CA1237771A - Sensor array for toxic gas detection - Google Patents
Sensor array for toxic gas detectionInfo
- Publication number
- CA1237771A CA1237771A CA000474463A CA474463A CA1237771A CA 1237771 A CA1237771 A CA 1237771A CA 000474463 A CA000474463 A CA 000474463A CA 474463 A CA474463 A CA 474463A CA 1237771 A CA1237771 A CA 1237771A
- Authority
- CA
- Canada
- Prior art keywords
- sensors
- instrument
- response
- component
- array
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/78—Detectors specially adapted therefor using more than one detector
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/88—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
- G01N2030/8881—Modular construction, specially adapted therefor
Abstract
ABSTRACT
A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas form a pattern of electrical responses, a source standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display.
The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.
A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas form a pattern of electrical responses, a source standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display.
The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.
Description
AYE f This invention relates to analytical devices and more particularly to devices for detecting the presence of at least one pollutant or other hazardous component in a gas sample. The invention further roulettes to a device having a plurality of individual electrical responses from a plurality OX sensors with the responses forming a pattern characteristic of a hazardous component More specifically the invention relates to a portable instrument capable or being used in field locations for detecting and identifying at least one hazardous component in a gas by a comparison of the pattern of responses from the sensors with one or more standard patterns stored in a memory in the instrument Particularly with respect to use at field locations for chemical spills and the like, devices for detecting the presence of a pollutant or other hazardous component in a gas have generally been associated with a particular selected compound. Detection devices selective for hydrogen sulfide, carbon monoxide, ammonia, and the like may be considered as representative. Essentially, these devices measure one or a few selected pollutants and are not designed to identify the pollutant. When a gas for analysis '7 71 may contain an unknown pollutant, it is usually necessary to obtain a sample of the gas and send it to a laboratory for a remote analysis. The time required for the transmittal of the sample and its analysis usually delays a meaningful identification of any hzrLlful components and/or their concentration in the gas for a significant time.
Semi-portable versions Or the more powerful laboratory gas chronatographic or infrared analyzers have been commercially introduced in recent years. Besides being rather heavy, bulky, unwieldy, and expensive, these instruments have certain inherent limitations. The gas chromatographic devices cannot operate in a continuous real-time monitoring mode. The infrared analyzers require a delicate optical system with a rather long absorption path, which contributes to their bulk, weight, and unwieldiness.
these instruments must usually be operated and their results interpreted only by well-trained professionals.
One object of this invention is a device for detecting and identifying one or more hazardous components of a gas.
A second object of this invention is a device capable of identifying a hazardous component in a gas from the response pattern of a plurality of sensors. A third object of the invention is a device .-or identifying any Ox a number of unknown hazardous componeilts in a gas. Another object of the invention is a device capable of providing a vatted pattern of responses and thereby capable of identifying a plurality of possible hazardous components in a gas. An additional object of the invention is a device capable of on-site analysis of a was. A further object of the invention is a portable device capable of being easily transported to filial locations and of being operated and used by unskilled or semi-skilled personnel.
Briefly, the invention relates to an analytical device for identifying at least one hazardous component in à gas such as air through the use of an array of small, preferably tiny sensors such as existing electrochemical, semiconductor, heated noble metal catalyst, or photo ionization sensors, To has been found that the pattern of responses from these sensors provides identification. of the component when compared to a standard response pattern which may be established for the component in the memory of the device. In the device, at least two of the sensors produce different electrical responses from the chemical interaction of the component or its derivative with each sensor. The array preferably also includes at least ogle heating filament capable of producing one or more derivatives by oxidation or pyrolyzes of the component. In addition, the responses from the sensors may be varied by changes in one or more of the operational conditions such as voltage, temperature, sample flow rate, or diversion of the sample flow through a selective chemical filter, and the like, so that the number of d fferent responses is greater than the number of sensors and the number of components in the gas. 'this increase in the number of different responses improves the selectivity o the device with respect to the identification of the hazardous components.
1~3 iJ'7'~
The device is particularly useful as a small portable instrument suitable for use in the field for identifying one or more hazardous components from a chemical spill or other emergency condition. Programming means are provided to form a response pattern from the array of sensors and compare the formed response pattern with one or more standard response patterns stored in a memory in the instrument. In one em-bodiment, the device includes two different heating lit-amens and four different electrochemical sensors with programming means capable of changing at least one operating condition for the four electrochemical sensors to identify any one of over 50-100 hazardous components. In addition, analysis of the responses also provides data on the concern-traction levels of the hazardous component or components.
All these functions are self-contained in the instrument and are preprogrammed so that they may be carried out by general-lye unskilled personnel. In general, the instrument has a power requirement below about 2 watts and the sensors are en-ranged in a space less than about 8 cm by 15 cm by 8 cm.
The device further has the capability of continuously monitoring levels of a hazardous substance and triggering an alarm when a predetermined level is reached.
The present invention therefore provides a method for identifying at least one component in a gas sample, comprise in the steps of introducing a gas sample suspected of con-twining at least one component to an array of sensors for exposure of said component or a derivative thereof to said sensors, said array including plural sensors having dip-1~3 pa firing electrical responses to said at least one component or said derivative thereof dependent on the chemical interact lion of said at least one component or said derivative there-of with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors, changing said operational condition during the expo~
sure of said sensors to the gas sample to provide plural-fly of different responses from said at least one sensor, forming a response pattern from the responses of said son-sons, and comparing the formed response pattern with a set of previously established response patterns to identify said at least one component.
The invention also provides an instrument for identify-in at least one hazardous component in the gas sample, come prosing sensing means including an array of sensors, means for introducing to said sensing means a gas sample suspected of containing at least one hazardous component, said array including plural sensors having differing electrical no-spouses to said at least one component or a derivative there-of dependent on the chemical interaction of said component or a derivative thereof with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors, means for changing said operation-at condition during the exposure of said sensors to the gas sample to provide a plurality of different responses from said at least one sensor, means for forming a response pat-tern from said sensing means upon exposure to said sample, means for providing a plurality of previously established 1~3 I I
4b response patterns including a previously established response pattern for identifying said at least one component, and means for comparing the formed response pattern with at least one previously established response pattern to identify at least one component.
Figs. lo & lo are a series of graphs showing the no-spouse patterns for acrylonitrile from an array of sensors including four electrochemical sensors.
Fig. 2 is a series of graphs showing the response pat-terns to pardon from an array of sensors including fourelectrochemical sensors.
"3 Fig. 3 is a pair of histograms of normalized responses of 16 channels to toxic vapors of acrylonitrile and pardon.
Fig. 4 is a pair of graphs showing the proportionality of the response signals in the strongest channels of Fig. 3 to the sampled toxic vapor concentration.
Fig. 5 is a block diagram of one embodiment of the in-mention with a sensor array having sample chambers connected in series.
Fig. 6 is a block diagram of a second embodiment of the invention with a sensor array having sample chambers connect-Ed in parallel.
Figs. PA & 7B represent elevation views of a portable instrument.
Fig. 8 is a block diagram of the data generating and processing systems associated with the invention.
The invention is directed to a method and the associate Ed device for identifying at least one hazardous component in a gas. The invention is particularly important for use in the field as a portable instrument for detecting one or more hazardous components in air from a chemical spill, fire, or other form of pollution. Representative hazardous components with which the invention provides useful results include acrylonitrile, ammonia, Bunsen, carbon monoxide, carbon tetrachloride, chlorine, chloroform, cyclohexane, ethyl acrylate, formaldehyde, hydrogen sulfide, nitric oxide, nitrogen dioxide, nitromethane, pardon, 1~3'7~7 sulfur dioxide, sulfuryl fluoride, tetrahydrofuran, Tulane, and vinyl acetate.
The TAO (time-weighted average) toxic levels OX the above hazardous components vary from about 1 Pam (parts per million) for chlorine or formaldehyde to about 300 Pam for cvclohexane. However, for short term exposure, it may be more important to detect and identify one or more of these components at levels in the order of about 2 to 400 (usually 10 to 50) Pam. In the invention, these components are detected by their chemical interaction or that of their derivatives with the sensors in the array. Usually, the component has a chemically active group or groups or may be oxidized or reduced to form one or more derivatives having an active group or groups such as carbon monoxide, nitrogen dioxide, etc.
In the invention, each of the sensors in an array is provided with a housing or other gas containment system forming a sample chamber with the combination forming a sensing means. Ions are provided for introducing a gas sample to the sensing means which typically may be the sensing electrode of an electrochemical, especially of an amperometric, gas sensor. The sensors include at least two and preferably at least 3-4 sensors having different electrical responses to a component or its derivative to provide a plurality of different responses. Usually, the responses differ between sensors for the same component and between the same sensor for different components I 3'~'~7~
As an illustration of the operation of an instrumerlt embodying the invention, the instrument can be set to perform one of two principal functions -- monitoring or idcntificatioll. When monitoring for the presence of any unknown air contaminant, the sensor array is connected directly to a sampling probe, and a signal from any of the sensors indicates the presence of a possibly hazardous component near the probe intake. To identify the detected component, a sample is first drawn from the probe intake into a l-liter (L) sampling bag. The collected sample is then drawn through the sensor array at a rate of about 0.01-0.1 L per minute, and the sensors are switched into four differently selective modes at appropriate intervals (usually 40 seconds/interval). The responses o each sensor at the end of each interval are recorded in one of it independent data channels, and the relative magnitudes of these response signals provide the information needed to identify the particular component giving rise to the observed signals. The microprocessor-controller identifies a compound based on the recorded data and then sets the sensor array for maximum sensitivity to that compound in the monitoring mode. The number of sensors and time required may be varied according to the complexity of Lye analyze.
Simpler mixtures may require smaller arrays and fewer modes of operation than the more complex analyzes. It can also set the alarm to correspond to an appropriate level associated with the short term exposure limit (STEW.) or immediate danger to life and health (IDLY) concentration of the identified compound.
The sensor array may comprise electrochemical, catalyst-to or semiconductor-type sensors, or combinations of these and other types of portable low-power gas sensors, and prey-drably will be primarily electrochemical. The sensor array may also include one or more heating filaments having ox-posed catalytic surfaces. Suitable types of electrochemical sensors include amperometric sensors having gold or platinum sensing electrodes supported on either an ion-exchange, e.g., polyfluorosulfonic acid, membrane, which also serves as the sensor electrolyte, or on a gas-permeable electrolyte-impermeable porous polytetrafluoroethylene membrane, with the sensor electrolyte being either a strong acid, such as H2SO4 or POW, or a strong base, such as OH in aqueous solution. Sensors using other metal and non-metal electrodes in aqueous or non-aqueous solutions may also be used. The array may also include one or more heating filaments containing catalytic material, such as platinum, palladium, iridium, rhodium or gold, and preferably two separate filaments, e.g., one of platinum and one of rhodium. These filaments may function to provide different degrees of oxidation of the compound and also to act as sensors whose electrical current will vary with the concentration of the component.
When a gas sample is caused to flow past the filaments before being exposed to a sensor array, as indicated in of-then of Figs. 5 or 6, then the partial oxidation or I
pyrolyzes of a component caused by heating one of the lit-amens becomes equivalent to converting the sensor array to a differently selective operating mode.
An alternative or complementary way of increasing the number of differently selective operating modes, and thereby achieving improved selectivity, is to divert the sample past Jo I
one or more selective chemical fitters (e.g., cartridges con-twining materials having strong chemical affinity for con-lain compounds) by means of electronically controlled solenoid valves (not shown). Such fitters may comprise anti-voted charcoal or other adsorbent to remove organic vapors or chemical reagents such as triethanolamine on a support to remove nitrogen dioxide. By comparing the responses of the sensor array to a sample passed through no chemical filter with the responses to the same sample passed through one or more different chemical filters, identification of the test-Ed compound or compounds may be greatly facilitated.
In any case, for a number S of differently selective sensors in an array and a number M of differently selective operating modes, the maximum number of independent pram-ethers (or data channels) P that can be obtained upon expo-sure to a test sample is given by the product MS, i.e., P =
MS. The larger the value of P, the larger the number of dip-fervent components that can be identified by a sensor array.
As an illustration of the detection of hazardous combo-newts, Figs. I and 2 provide data for acrylonitrile andpyridine, respectively. The array includes four different electrochernical toxic gas sensors -- two with pure gold mesh sensing electrodes embedded in a polyfluorosulfonic acid ion-exchange membrane, one of the electrodes being kept a-t a potential 1.0 volt and one at a potential of 1.4 volt versus RYE (the reversible hydrogen electrode), one with a similar electrode made of platinized platinum mesh and kept at 1.3 volt versus THE and one with a sensing electrode of platinum I
pa black bonded to a porous tetrafluoroethylene membrane, imp messed in an approximately 25-30 wt.% sulfuric acid electron lyre, and potentiostated at 1.1 volt versus RYE -- and two heated noble metal filaments -- one of platinum and one of rhodium -- that function to oxidize or partially oxidize many compounds in air. The four sensors may be rapidly switched to one of the following four operating modes: (a) platinum filament heated to about 850C; (~) rhodium filament heated to about 900C; (c) rhodium filament heated to about 1000C; and (d) both filaments off. In this arrangement, four modes and four sensors provide a total of 16 independent data channels as illustrated in Figs. 1 and 3. In Fig. 1, each of four sensors was exposed to predetermined amounts of acrylonitrile ill air and was operating in each of the foregoing four modes. As indicated by the data, each sensor has a different electrical response pattern to exposure to acrylonitrile with the response changing with concentration. A similar result is shown in Fig. 2 for pardon. The responses in Figs. 1 and 2, when norr.lalized as set forth in Fig. 3, exhibit different histogram patterns for different compounds, thereby permitting identification of a sampled compound. Moreover, as illustrated in Fig. 4, the magnitude or amplitude of the strongest channels in Fig. 3 may be used as an indication of the concentration of the identified hazardous component.
Further with respect to Fig. 4, the data also show the tumid average threshold exposure level (To) and the STEW or IDLY concentrations of the two components.
The device may function either to monitor the level o a component or to identify unknown components. Fig. 3 shows that channel 6 provides the strongest signal for acrylonitrile while channel 7 provides the strongest signal for pardon. Therefore, the sensor array as a monitor will I 7'~'~7~
be tuned to channel 6 after having identified acrylonitrile or to channel 7 after having identified pardon.
Programming means are provided to form sensor responses into a response pattern. As illustrated in Fig. 3, the no-spouses may be positive, a-t or about zero, or negative.
These responses collectively form one or more response pat-terns which serve to identify the component.
Advantageously, the programming means include means for comparing the formed response pattern with one or more stank dart or previously established patterns each being character-fistic of a particular component or type of component.
Preferably, the programming means also include a memory which provides the standard patterns for the comparison.
Prior to the comparison, the initial or first response pattern is converted to a second pattern in which noise and blank readings are removed. As an illustration, the no-spouses in Fir,. 3 are obtained by dividing the responses in-tidally obtained by the corresponding toxic gas concentration and also by the average noise of each sensor corresponding to a given channel. The values in each channel are then nor-malized by dividing them by the highest response in the 16-channel response pattern to provide Fig. 3.
In environments where the number of possible detectable components exceeds the number P of independent parameters or data channels, gas samples containing mixtures of more than one unknown detectable component may be received To resolve such a mixture of unknown components in a gas same pie, tile programming means can first reject those candidate compounds whose response patterns call for significant sign nets in those channels in which the tested sample gave no significant response. In the examples of Figs. 1~3, an Jo insignificant response in Channel No. 1 (corresponding to Sensor No. 1 in Operating Mode No. I would exclude pardon as a candidate compound, but would be compatible with the presence of acrylonitrile. This can be followed by addition-at rescreening steps. For instance the programming means can then select those remaining candidate compounds whose no-spouse patterns exhibit strong responses in the same chant nets as in the actually observed response pattern. For instance, strong responses in Channel Nos. 5, 6 and 7 of Fig. 3, would point to acrylonitrile as a possible candidate compound. Finally, should this selection process yield more than one likely candidate compound, then the concentrations of each of these likely candidates may be estimated by solve in several simultaneous algebraic equations (developed from an analysis of the standard response pattern) based on a come prison of the actual response pattern with the response pat-terns of the likely candidate compounds. All of these comparisons can be performed rapidly using a microprocessor built into the instrument.
Fig. 5 and 6 provide schematic sketches of sensor array arrangements. As illustrated in Fig. 5, the sample inlet 10 includes pump I to cause a flow of sample to filaments 13 and 14 which may be individually switched on or off or both or. and off during the analysis. Filter 15 is provided to no-move particulate. The resulting sample may be the initial component or its derivative or derivatives depending on whether filaments 13 and/or 14 are utilized. The resulting sample is then fed sequentially to sensors 16, 17, ~'7'~71 18 and 19. These sensors are also arranged so that the first few sensors in the sequence interact with only minimal amounts of the sample without significantly altering the concentration introduced into the sample chambers of the subsequent sensors.
In Fix. 6, the sample is fed to filaments 40 arid 41 and then to sensors 42, 43, 44 and 45 arranged in parallel.
After interacting with these sensors, the sample is removed via pump 46. Data acquisition and potentiostat circuits 47 are provided to receive the responses and provide changes in the voltages of the sensors.
Fig. PA and 7B provides at arrangement of side and front views of a portable instrument. As illustrated, a housing 50 is provided which may be about 8 cm. by 28 cm. by 22 cm. ~lectrochemical cells 51 and filament 52 are provided as the array. Pump 53 acts to introduce the sample. Batteries 54 provide portable power. Filter 55 acts to remove particles. Four circuit boards are provided.
Board 56 provides the CPU (central processing unit), board 57 provides the potentiometer and self-test circuits, board 58 provides the analog circuit, and board 59 provides power, alarm and display circuits. Display module 60 provides a display of data from each test.
Fig. 8 illustrates the interconnection of the parts of the device. Electrochemical ceils 70 are controlled by potentiostats 71 with the responses from cells 70 being fed to an analog input/output 72 which also receives data anger instructions from oxygen sensor 73, alarm 74, flammable gas sensor 75, filament control 77, and CPU 78. Digital input-output 79 also is operated by switch register 80, battery monitor 76, filament control 77, CPU 78, and pump control 81. Display and alarm signals are provided by digital in-put/output 79.
The device is provided with microprocessor programming means in which a master program is used to select any of a plurality of functional programs which in turn may utilize one or more of certain of the other functional programs and one or more utility programs. Selection of the functional program in the preferred embodiment is by the use of an apt propriety key on the face of the housing. A display is pro-voided to show the name of the component identified by the programming means in the test or the component being monitored.
In one preferred embodiment, the functional programs are named the Indent mode, the Select mode, the Universal mode, the Zero mode, the Calibrate mode, and the Test mode.
All of these programs are operated using key strokes by the individual operators that activate the microprocessor to run the desired program. As illustrations of these modes, the following description is provided with the term "gas" intend-Ed to refer to the "component" being detected.
The Indent mode collects a set of data from an unknown gas (16 data points, 4 electrochemical cells in 4 modes), subtracts a set of zero data (the signals obtained from background air), multiplies by calibration data (obtained from a calibration gas to take into account -the changing 7 7 ;' .
performance of cells, if any, and by treating the result as a 16-coordinate equator, compares the data to a series of pattern data sets stored in a library for various gases (the unknown gas data is normalized, and a Euclidian distance calculation is performed between it and every pattern set).
The gas having the pattern data which is the closest to the unknown is selected as the proper identification for the gas, and any pattern data sets having a distance from the unknown equal to or less than twice the minimum distance are lo selected as possible or incipient identifications. The concentratioll of the gas is calculated by multiplying the data front the strongest channel by a concentration coefficient stored in the pattern data library, and from the results of this calculation the percent IDLY level is also determined. All of this information is displayed, and alarms are set off at the 25% and 100% IDLY level (a beeping buzzer and flashing Lids (light-emittin~ diodes) at 25% or greater, and a steady buzzer and Lids at 100% and higher).
Finally, the option is provided to the operator to review Thea information (gas identified, concentration, percent IDLY, number of incipient misidentifications, and a sty of incipient misidentifications) or to exit back to master program or a routine "fain" by pressing the proper key.
Exiting back to Main shuts off any alarms.
The Select move allows the operator to choose which of the gases in the pattern library to monitor. The gas is chosen by advancing forwards or backwards through the library, using the keyboard (only the name of the gas is 12~7771 displayed. When the proper gas is located, the operator can choose to either initiate the mode or exit back to MAIN
Once initiated, the device is operated only in the most sensitive mode, so that only four channels of data are taken. The Euclidian distance is calculated based on only four channels to give a measure of how well the measured gas fits the pattern vector. This feature is intended to warn of mixtures of vapors or of mislabeling of chemicals.
Select mode provides a measurement in a time appropriate for the mode (32 to 50 sea). The program may be interrupted after any cycle.
The Universal mode is to detect possibly hazardous compounds prior to their identification. A Pi or Rho filament cycles on and off with sickened duty cycles.
'he sensor responses are reported to the operator as a set of four arbitrary numbers; the alarm is triggered when any cell output exceeds a predetermined threshold.
The no-signal state of the device must be frequently measured. Upon entering the Zero mode, the 16 chanTIels of information are acquired using the same routine (Volts) that is called by the Indent mode. Afterward, the 16-element vector is transferred to a special resister. In subsequent measurements, this value is subtracted front all incoming data in the Into, Select, or Universal modes.
Sir.lilarly, the aging of electrochemical cells and filaments is expected to cause gradual changes in responses over tire. The Calibrate mode is designed to calculate a correction factor for each channel. A sample of a I
calibration gas such as sulfur dioxide is attached to the device. The data acquisition subroutine (Volts) is called.
The resulting vector is compared to that stored in the pattern library, and the ratio is stored in a special register. Each subsequent measurement in the Indent or Select modes is corrected by this ratio. If Caleb is not selected, a default vector is loaded into the calibrate register, representing the state of the cells at the time the library was compiled.
The lest mode gives access to the same monitor program that was used in program development on the device. The monitor program permits these functions.
(a) Reading any portion of memory.
(b) Changing values in ROY memory.
(c) Resetting the instrument.
(d) Calling certain subroutines used for device testing. For example, Control can be used to manually control pump speed and both filaments.
Test mode is not intended for routine operator use. of Test mode is inadvertently entered, two keystrokes will escape this mode.
As covered by the abcsve disclosure, the invention provides an analytical device useful in the field for performing the three functions of detecting, identifying and measuring a component in a gas. Advantageously, the device is portable and includes microprocessor programming means by which multiple functions may be carried out with respect to 1~3'^~'7~
I
a gas component and the results depicted on a display on the device.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching.
Semi-portable versions Or the more powerful laboratory gas chronatographic or infrared analyzers have been commercially introduced in recent years. Besides being rather heavy, bulky, unwieldy, and expensive, these instruments have certain inherent limitations. The gas chromatographic devices cannot operate in a continuous real-time monitoring mode. The infrared analyzers require a delicate optical system with a rather long absorption path, which contributes to their bulk, weight, and unwieldiness.
these instruments must usually be operated and their results interpreted only by well-trained professionals.
One object of this invention is a device for detecting and identifying one or more hazardous components of a gas.
A second object of this invention is a device capable of identifying a hazardous component in a gas from the response pattern of a plurality of sensors. A third object of the invention is a device .-or identifying any Ox a number of unknown hazardous componeilts in a gas. Another object of the invention is a device capable of providing a vatted pattern of responses and thereby capable of identifying a plurality of possible hazardous components in a gas. An additional object of the invention is a device capable of on-site analysis of a was. A further object of the invention is a portable device capable of being easily transported to filial locations and of being operated and used by unskilled or semi-skilled personnel.
Briefly, the invention relates to an analytical device for identifying at least one hazardous component in à gas such as air through the use of an array of small, preferably tiny sensors such as existing electrochemical, semiconductor, heated noble metal catalyst, or photo ionization sensors, To has been found that the pattern of responses from these sensors provides identification. of the component when compared to a standard response pattern which may be established for the component in the memory of the device. In the device, at least two of the sensors produce different electrical responses from the chemical interaction of the component or its derivative with each sensor. The array preferably also includes at least ogle heating filament capable of producing one or more derivatives by oxidation or pyrolyzes of the component. In addition, the responses from the sensors may be varied by changes in one or more of the operational conditions such as voltage, temperature, sample flow rate, or diversion of the sample flow through a selective chemical filter, and the like, so that the number of d fferent responses is greater than the number of sensors and the number of components in the gas. 'this increase in the number of different responses improves the selectivity o the device with respect to the identification of the hazardous components.
1~3 iJ'7'~
The device is particularly useful as a small portable instrument suitable for use in the field for identifying one or more hazardous components from a chemical spill or other emergency condition. Programming means are provided to form a response pattern from the array of sensors and compare the formed response pattern with one or more standard response patterns stored in a memory in the instrument. In one em-bodiment, the device includes two different heating lit-amens and four different electrochemical sensors with programming means capable of changing at least one operating condition for the four electrochemical sensors to identify any one of over 50-100 hazardous components. In addition, analysis of the responses also provides data on the concern-traction levels of the hazardous component or components.
All these functions are self-contained in the instrument and are preprogrammed so that they may be carried out by general-lye unskilled personnel. In general, the instrument has a power requirement below about 2 watts and the sensors are en-ranged in a space less than about 8 cm by 15 cm by 8 cm.
The device further has the capability of continuously monitoring levels of a hazardous substance and triggering an alarm when a predetermined level is reached.
The present invention therefore provides a method for identifying at least one component in a gas sample, comprise in the steps of introducing a gas sample suspected of con-twining at least one component to an array of sensors for exposure of said component or a derivative thereof to said sensors, said array including plural sensors having dip-1~3 pa firing electrical responses to said at least one component or said derivative thereof dependent on the chemical interact lion of said at least one component or said derivative there-of with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors, changing said operational condition during the expo~
sure of said sensors to the gas sample to provide plural-fly of different responses from said at least one sensor, forming a response pattern from the responses of said son-sons, and comparing the formed response pattern with a set of previously established response patterns to identify said at least one component.
The invention also provides an instrument for identify-in at least one hazardous component in the gas sample, come prosing sensing means including an array of sensors, means for introducing to said sensing means a gas sample suspected of containing at least one hazardous component, said array including plural sensors having differing electrical no-spouses to said at least one component or a derivative there-of dependent on the chemical interaction of said component or a derivative thereof with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors, means for changing said operation-at condition during the exposure of said sensors to the gas sample to provide a plurality of different responses from said at least one sensor, means for forming a response pat-tern from said sensing means upon exposure to said sample, means for providing a plurality of previously established 1~3 I I
4b response patterns including a previously established response pattern for identifying said at least one component, and means for comparing the formed response pattern with at least one previously established response pattern to identify at least one component.
Figs. lo & lo are a series of graphs showing the no-spouse patterns for acrylonitrile from an array of sensors including four electrochemical sensors.
Fig. 2 is a series of graphs showing the response pat-terns to pardon from an array of sensors including fourelectrochemical sensors.
"3 Fig. 3 is a pair of histograms of normalized responses of 16 channels to toxic vapors of acrylonitrile and pardon.
Fig. 4 is a pair of graphs showing the proportionality of the response signals in the strongest channels of Fig. 3 to the sampled toxic vapor concentration.
Fig. 5 is a block diagram of one embodiment of the in-mention with a sensor array having sample chambers connected in series.
Fig. 6 is a block diagram of a second embodiment of the invention with a sensor array having sample chambers connect-Ed in parallel.
Figs. PA & 7B represent elevation views of a portable instrument.
Fig. 8 is a block diagram of the data generating and processing systems associated with the invention.
The invention is directed to a method and the associate Ed device for identifying at least one hazardous component in a gas. The invention is particularly important for use in the field as a portable instrument for detecting one or more hazardous components in air from a chemical spill, fire, or other form of pollution. Representative hazardous components with which the invention provides useful results include acrylonitrile, ammonia, Bunsen, carbon monoxide, carbon tetrachloride, chlorine, chloroform, cyclohexane, ethyl acrylate, formaldehyde, hydrogen sulfide, nitric oxide, nitrogen dioxide, nitromethane, pardon, 1~3'7~7 sulfur dioxide, sulfuryl fluoride, tetrahydrofuran, Tulane, and vinyl acetate.
The TAO (time-weighted average) toxic levels OX the above hazardous components vary from about 1 Pam (parts per million) for chlorine or formaldehyde to about 300 Pam for cvclohexane. However, for short term exposure, it may be more important to detect and identify one or more of these components at levels in the order of about 2 to 400 (usually 10 to 50) Pam. In the invention, these components are detected by their chemical interaction or that of their derivatives with the sensors in the array. Usually, the component has a chemically active group or groups or may be oxidized or reduced to form one or more derivatives having an active group or groups such as carbon monoxide, nitrogen dioxide, etc.
In the invention, each of the sensors in an array is provided with a housing or other gas containment system forming a sample chamber with the combination forming a sensing means. Ions are provided for introducing a gas sample to the sensing means which typically may be the sensing electrode of an electrochemical, especially of an amperometric, gas sensor. The sensors include at least two and preferably at least 3-4 sensors having different electrical responses to a component or its derivative to provide a plurality of different responses. Usually, the responses differ between sensors for the same component and between the same sensor for different components I 3'~'~7~
As an illustration of the operation of an instrumerlt embodying the invention, the instrument can be set to perform one of two principal functions -- monitoring or idcntificatioll. When monitoring for the presence of any unknown air contaminant, the sensor array is connected directly to a sampling probe, and a signal from any of the sensors indicates the presence of a possibly hazardous component near the probe intake. To identify the detected component, a sample is first drawn from the probe intake into a l-liter (L) sampling bag. The collected sample is then drawn through the sensor array at a rate of about 0.01-0.1 L per minute, and the sensors are switched into four differently selective modes at appropriate intervals (usually 40 seconds/interval). The responses o each sensor at the end of each interval are recorded in one of it independent data channels, and the relative magnitudes of these response signals provide the information needed to identify the particular component giving rise to the observed signals. The microprocessor-controller identifies a compound based on the recorded data and then sets the sensor array for maximum sensitivity to that compound in the monitoring mode. The number of sensors and time required may be varied according to the complexity of Lye analyze.
Simpler mixtures may require smaller arrays and fewer modes of operation than the more complex analyzes. It can also set the alarm to correspond to an appropriate level associated with the short term exposure limit (STEW.) or immediate danger to life and health (IDLY) concentration of the identified compound.
The sensor array may comprise electrochemical, catalyst-to or semiconductor-type sensors, or combinations of these and other types of portable low-power gas sensors, and prey-drably will be primarily electrochemical. The sensor array may also include one or more heating filaments having ox-posed catalytic surfaces. Suitable types of electrochemical sensors include amperometric sensors having gold or platinum sensing electrodes supported on either an ion-exchange, e.g., polyfluorosulfonic acid, membrane, which also serves as the sensor electrolyte, or on a gas-permeable electrolyte-impermeable porous polytetrafluoroethylene membrane, with the sensor electrolyte being either a strong acid, such as H2SO4 or POW, or a strong base, such as OH in aqueous solution. Sensors using other metal and non-metal electrodes in aqueous or non-aqueous solutions may also be used. The array may also include one or more heating filaments containing catalytic material, such as platinum, palladium, iridium, rhodium or gold, and preferably two separate filaments, e.g., one of platinum and one of rhodium. These filaments may function to provide different degrees of oxidation of the compound and also to act as sensors whose electrical current will vary with the concentration of the component.
When a gas sample is caused to flow past the filaments before being exposed to a sensor array, as indicated in of-then of Figs. 5 or 6, then the partial oxidation or I
pyrolyzes of a component caused by heating one of the lit-amens becomes equivalent to converting the sensor array to a differently selective operating mode.
An alternative or complementary way of increasing the number of differently selective operating modes, and thereby achieving improved selectivity, is to divert the sample past Jo I
one or more selective chemical fitters (e.g., cartridges con-twining materials having strong chemical affinity for con-lain compounds) by means of electronically controlled solenoid valves (not shown). Such fitters may comprise anti-voted charcoal or other adsorbent to remove organic vapors or chemical reagents such as triethanolamine on a support to remove nitrogen dioxide. By comparing the responses of the sensor array to a sample passed through no chemical filter with the responses to the same sample passed through one or more different chemical filters, identification of the test-Ed compound or compounds may be greatly facilitated.
In any case, for a number S of differently selective sensors in an array and a number M of differently selective operating modes, the maximum number of independent pram-ethers (or data channels) P that can be obtained upon expo-sure to a test sample is given by the product MS, i.e., P =
MS. The larger the value of P, the larger the number of dip-fervent components that can be identified by a sensor array.
As an illustration of the detection of hazardous combo-newts, Figs. I and 2 provide data for acrylonitrile andpyridine, respectively. The array includes four different electrochernical toxic gas sensors -- two with pure gold mesh sensing electrodes embedded in a polyfluorosulfonic acid ion-exchange membrane, one of the electrodes being kept a-t a potential 1.0 volt and one at a potential of 1.4 volt versus RYE (the reversible hydrogen electrode), one with a similar electrode made of platinized platinum mesh and kept at 1.3 volt versus THE and one with a sensing electrode of platinum I
pa black bonded to a porous tetrafluoroethylene membrane, imp messed in an approximately 25-30 wt.% sulfuric acid electron lyre, and potentiostated at 1.1 volt versus RYE -- and two heated noble metal filaments -- one of platinum and one of rhodium -- that function to oxidize or partially oxidize many compounds in air. The four sensors may be rapidly switched to one of the following four operating modes: (a) platinum filament heated to about 850C; (~) rhodium filament heated to about 900C; (c) rhodium filament heated to about 1000C; and (d) both filaments off. In this arrangement, four modes and four sensors provide a total of 16 independent data channels as illustrated in Figs. 1 and 3. In Fig. 1, each of four sensors was exposed to predetermined amounts of acrylonitrile ill air and was operating in each of the foregoing four modes. As indicated by the data, each sensor has a different electrical response pattern to exposure to acrylonitrile with the response changing with concentration. A similar result is shown in Fig. 2 for pardon. The responses in Figs. 1 and 2, when norr.lalized as set forth in Fig. 3, exhibit different histogram patterns for different compounds, thereby permitting identification of a sampled compound. Moreover, as illustrated in Fig. 4, the magnitude or amplitude of the strongest channels in Fig. 3 may be used as an indication of the concentration of the identified hazardous component.
Further with respect to Fig. 4, the data also show the tumid average threshold exposure level (To) and the STEW or IDLY concentrations of the two components.
The device may function either to monitor the level o a component or to identify unknown components. Fig. 3 shows that channel 6 provides the strongest signal for acrylonitrile while channel 7 provides the strongest signal for pardon. Therefore, the sensor array as a monitor will I 7'~'~7~
be tuned to channel 6 after having identified acrylonitrile or to channel 7 after having identified pardon.
Programming means are provided to form sensor responses into a response pattern. As illustrated in Fig. 3, the no-spouses may be positive, a-t or about zero, or negative.
These responses collectively form one or more response pat-terns which serve to identify the component.
Advantageously, the programming means include means for comparing the formed response pattern with one or more stank dart or previously established patterns each being character-fistic of a particular component or type of component.
Preferably, the programming means also include a memory which provides the standard patterns for the comparison.
Prior to the comparison, the initial or first response pattern is converted to a second pattern in which noise and blank readings are removed. As an illustration, the no-spouses in Fir,. 3 are obtained by dividing the responses in-tidally obtained by the corresponding toxic gas concentration and also by the average noise of each sensor corresponding to a given channel. The values in each channel are then nor-malized by dividing them by the highest response in the 16-channel response pattern to provide Fig. 3.
In environments where the number of possible detectable components exceeds the number P of independent parameters or data channels, gas samples containing mixtures of more than one unknown detectable component may be received To resolve such a mixture of unknown components in a gas same pie, tile programming means can first reject those candidate compounds whose response patterns call for significant sign nets in those channels in which the tested sample gave no significant response. In the examples of Figs. 1~3, an Jo insignificant response in Channel No. 1 (corresponding to Sensor No. 1 in Operating Mode No. I would exclude pardon as a candidate compound, but would be compatible with the presence of acrylonitrile. This can be followed by addition-at rescreening steps. For instance the programming means can then select those remaining candidate compounds whose no-spouse patterns exhibit strong responses in the same chant nets as in the actually observed response pattern. For instance, strong responses in Channel Nos. 5, 6 and 7 of Fig. 3, would point to acrylonitrile as a possible candidate compound. Finally, should this selection process yield more than one likely candidate compound, then the concentrations of each of these likely candidates may be estimated by solve in several simultaneous algebraic equations (developed from an analysis of the standard response pattern) based on a come prison of the actual response pattern with the response pat-terns of the likely candidate compounds. All of these comparisons can be performed rapidly using a microprocessor built into the instrument.
Fig. 5 and 6 provide schematic sketches of sensor array arrangements. As illustrated in Fig. 5, the sample inlet 10 includes pump I to cause a flow of sample to filaments 13 and 14 which may be individually switched on or off or both or. and off during the analysis. Filter 15 is provided to no-move particulate. The resulting sample may be the initial component or its derivative or derivatives depending on whether filaments 13 and/or 14 are utilized. The resulting sample is then fed sequentially to sensors 16, 17, ~'7'~71 18 and 19. These sensors are also arranged so that the first few sensors in the sequence interact with only minimal amounts of the sample without significantly altering the concentration introduced into the sample chambers of the subsequent sensors.
In Fix. 6, the sample is fed to filaments 40 arid 41 and then to sensors 42, 43, 44 and 45 arranged in parallel.
After interacting with these sensors, the sample is removed via pump 46. Data acquisition and potentiostat circuits 47 are provided to receive the responses and provide changes in the voltages of the sensors.
Fig. PA and 7B provides at arrangement of side and front views of a portable instrument. As illustrated, a housing 50 is provided which may be about 8 cm. by 28 cm. by 22 cm. ~lectrochemical cells 51 and filament 52 are provided as the array. Pump 53 acts to introduce the sample. Batteries 54 provide portable power. Filter 55 acts to remove particles. Four circuit boards are provided.
Board 56 provides the CPU (central processing unit), board 57 provides the potentiometer and self-test circuits, board 58 provides the analog circuit, and board 59 provides power, alarm and display circuits. Display module 60 provides a display of data from each test.
Fig. 8 illustrates the interconnection of the parts of the device. Electrochemical ceils 70 are controlled by potentiostats 71 with the responses from cells 70 being fed to an analog input/output 72 which also receives data anger instructions from oxygen sensor 73, alarm 74, flammable gas sensor 75, filament control 77, and CPU 78. Digital input-output 79 also is operated by switch register 80, battery monitor 76, filament control 77, CPU 78, and pump control 81. Display and alarm signals are provided by digital in-put/output 79.
The device is provided with microprocessor programming means in which a master program is used to select any of a plurality of functional programs which in turn may utilize one or more of certain of the other functional programs and one or more utility programs. Selection of the functional program in the preferred embodiment is by the use of an apt propriety key on the face of the housing. A display is pro-voided to show the name of the component identified by the programming means in the test or the component being monitored.
In one preferred embodiment, the functional programs are named the Indent mode, the Select mode, the Universal mode, the Zero mode, the Calibrate mode, and the Test mode.
All of these programs are operated using key strokes by the individual operators that activate the microprocessor to run the desired program. As illustrations of these modes, the following description is provided with the term "gas" intend-Ed to refer to the "component" being detected.
The Indent mode collects a set of data from an unknown gas (16 data points, 4 electrochemical cells in 4 modes), subtracts a set of zero data (the signals obtained from background air), multiplies by calibration data (obtained from a calibration gas to take into account -the changing 7 7 ;' .
performance of cells, if any, and by treating the result as a 16-coordinate equator, compares the data to a series of pattern data sets stored in a library for various gases (the unknown gas data is normalized, and a Euclidian distance calculation is performed between it and every pattern set).
The gas having the pattern data which is the closest to the unknown is selected as the proper identification for the gas, and any pattern data sets having a distance from the unknown equal to or less than twice the minimum distance are lo selected as possible or incipient identifications. The concentratioll of the gas is calculated by multiplying the data front the strongest channel by a concentration coefficient stored in the pattern data library, and from the results of this calculation the percent IDLY level is also determined. All of this information is displayed, and alarms are set off at the 25% and 100% IDLY level (a beeping buzzer and flashing Lids (light-emittin~ diodes) at 25% or greater, and a steady buzzer and Lids at 100% and higher).
Finally, the option is provided to the operator to review Thea information (gas identified, concentration, percent IDLY, number of incipient misidentifications, and a sty of incipient misidentifications) or to exit back to master program or a routine "fain" by pressing the proper key.
Exiting back to Main shuts off any alarms.
The Select move allows the operator to choose which of the gases in the pattern library to monitor. The gas is chosen by advancing forwards or backwards through the library, using the keyboard (only the name of the gas is 12~7771 displayed. When the proper gas is located, the operator can choose to either initiate the mode or exit back to MAIN
Once initiated, the device is operated only in the most sensitive mode, so that only four channels of data are taken. The Euclidian distance is calculated based on only four channels to give a measure of how well the measured gas fits the pattern vector. This feature is intended to warn of mixtures of vapors or of mislabeling of chemicals.
Select mode provides a measurement in a time appropriate for the mode (32 to 50 sea). The program may be interrupted after any cycle.
The Universal mode is to detect possibly hazardous compounds prior to their identification. A Pi or Rho filament cycles on and off with sickened duty cycles.
'he sensor responses are reported to the operator as a set of four arbitrary numbers; the alarm is triggered when any cell output exceeds a predetermined threshold.
The no-signal state of the device must be frequently measured. Upon entering the Zero mode, the 16 chanTIels of information are acquired using the same routine (Volts) that is called by the Indent mode. Afterward, the 16-element vector is transferred to a special resister. In subsequent measurements, this value is subtracted front all incoming data in the Into, Select, or Universal modes.
Sir.lilarly, the aging of electrochemical cells and filaments is expected to cause gradual changes in responses over tire. The Calibrate mode is designed to calculate a correction factor for each channel. A sample of a I
calibration gas such as sulfur dioxide is attached to the device. The data acquisition subroutine (Volts) is called.
The resulting vector is compared to that stored in the pattern library, and the ratio is stored in a special register. Each subsequent measurement in the Indent or Select modes is corrected by this ratio. If Caleb is not selected, a default vector is loaded into the calibrate register, representing the state of the cells at the time the library was compiled.
The lest mode gives access to the same monitor program that was used in program development on the device. The monitor program permits these functions.
(a) Reading any portion of memory.
(b) Changing values in ROY memory.
(c) Resetting the instrument.
(d) Calling certain subroutines used for device testing. For example, Control can be used to manually control pump speed and both filaments.
Test mode is not intended for routine operator use. of Test mode is inadvertently entered, two keystrokes will escape this mode.
As covered by the abcsve disclosure, the invention provides an analytical device useful in the field for performing the three functions of detecting, identifying and measuring a component in a gas. Advantageously, the device is portable and includes microprocessor programming means by which multiple functions may be carried out with respect to 1~3'^~'7~
I
a gas component and the results depicted on a display on the device.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching.
Claims (28)
1. A method for identifying at least one component in a gas sample, comprising the steps of:
introducing a gas sample suspected of containing a least one component to an array of sensors for exposure of said component or a derivative thereof to said sensors, said array including plural sensors having differing electrical responses to said at least one component or said derivative thereof dependent on the chemical interaction of said at least one component or said derivative thereof with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors;
changing said operational condition during the exposure of said sensors to the gas sample to provide a plurality of different responses from said at least one sensor, forming a response pattern from the responses of said sensors, and comparing the formed response pattern with a set of pre-viously established response patterns to identify said at least one component.
introducing a gas sample suspected of containing a least one component to an array of sensors for exposure of said component or a derivative thereof to said sensors, said array including plural sensors having differing electrical responses to said at least one component or said derivative thereof dependent on the chemical interaction of said at least one component or said derivative thereof with each of said sensors and also dependent on an operational condition of at least one of said plurality of sensors;
changing said operational condition during the exposure of said sensors to the gas sample to provide a plurality of different responses from said at least one sensor, forming a response pattern from the responses of said sensors, and comparing the formed response pattern with a set of pre-viously established response patterns to identify said at least one component.
2. The method of Claim 1 wherein the total number of components that can be detected is greater than the product of the number of sensors times the number of different oper-ational conditions.
3. The method of Claim 1 wherein the step of forming the response pattern includes the step of converting a first response pattern to a second response pattern.
4. The method of Claim 1 wherein the step of compar-ing includes comparing the formed response pattern with a plurality of previously established response patterns, and further includes the step of first eliminating at least one of said plurality of previously established response pattern by comparing an insignificant response of said at least one sensor for one operational condition with said at least one previously established response pattern having a significant response for said at least one sensor for the same operational condition.
5. The method of Claim 1 wherein the changing of the operational condition is carried out to provide a plurality of responses greater in number than the number of said sen-sors and not smaller than the number of components to be identified in said gas.
6. The method of Claim 1 wherein the step of forming said response pattern results in at least one response pat-tern identifiable with a concentration of said at least one component and said step of comparing response patterns pro-vides a comparison of said at least one response pattern with a previously established response pattern for determin-ing said concentration.
7. The method of Claim 1 including the step of provid-ing a portable device including said array of sensors and wherein the formation and comparison of the response pattern are carried out with the device in the field.
8. An instrument for identifying at least one hazard-ous component in a gas sample, comprising sensing means including an array of sensors, means for introducing to said sensing means a gas sam-ple suspected of containing at least one hazardous component, said array including plural sensors having differing electrical responses to said at least one component or a de-rivative thereof dependent on the chemical interaction of said component or a derivative thereof with each of said sen-sors and also dependent on an operational condition of at least one of said plurality of sensors, means for changing said operational condition during the exposure of said sensors to the gas sample to provide a plurality of different responses from said at least one sensor, means for forming a response pattern from said sensing means upon exposure to said sample, means for providing a plurality of previously estab-lished response patterns including a previously established response pattern for identifying said at least one compo-nent, and means for comparing the formed response pattern with at least one previously established response pattern to identi-fy said at least one component.
9. The instrument of Claim 8 wherein said array in-cludes a heating filament in addition to said sensors, said heating filament being capable of forming a derivative of said at least one component.
10. The instrument of Claim 8 wherein said array in-cludes four sensors, each of said four sensors having elec-trical responses differing from those of the others of said four sensors.
11. The instrument of Claim 8 wherein said changing means enables said at least one sensor to provide more than one response.
12. The instrument of Claim 11 wherein said changing means enables each of a plurality of said sensors to provide more than one response with the number of responses for said array of sensors being greater than the number of said sensors.
13. The instrument of Claim 8 having means for provid-ing electrical power of up to about 2 watts.
14. The instrument of Claim 8 including programming means for selectively identifying an unknown component or monitoring the concentration of a known component of the gas.
15. The instrument of Claim 14 wherein said program-ming means includes means for mathematically modifying the responses for sensor calibration and background noise.
16. The instrument of Claim 12 wherein said array of sensors is arranged in a space less than about 8 cm by 15 cm by 8 cm.
17. The instrument of Claim 8 including a carrying case including electrical power means, said array of sen-sors, said means for forming said response pattern, memory means for storing said previously established response pat-terns, and said comparison means.
18. The instrument of Claim 16, wherein said power means includes at least one electrical battery.
19. The instrument of Claim 12 wherein said sensors in-clude a plurality of electrochemical sensors.
20. The instrument of Claim 11 wherein said sensors in-clude at least one semiconductor sensor.
21. The instrument of Claim 11 wherein said changing means comprises at least one heating filament disposed up-stream from said array of sensors.
22. The instrument of Claim 21 wherein said array is arranged with the sensors having the higher responses down-stream from the other sensors.
23. The instrument of Claim 8 wherein said sensing means includes two different heating filaments and four dif-ferent electrochemical sensors.
24. The instrument of Claim 8 wherein said forming means includes means for converting a first response pattern to a second response pattern prior to the comparison of patterns.
25. The instrument of Claim 8 wherein said comparing means includes means for comparing an insignificant response of said at least one sensor for one operational condition with a previously established response pattern having a sig-nificant response for said at least one sensor for the same operational condition.
6. The instrument of Claim 8 wherein said changing means comprises means for diverting said sample past a chem-ically selective filter.
27. An instrument for identifying and estimating the concentrations of a plurality of components in a gas sample, comprising:
sensing means including an array of differently selec-tive sensors, means for introducing to said sensing means a gas sam-ple possibly containing one or more components of a predeter-mined number of components that are detectable by said array, the number of said sensors being greater than one and fewer than said predetermined number, means for forming a multi-channel response pattern from said sensing means upon exposure to said sample, means for comparing said formed pattern with a set of previously established patterns, said comparing means including means for eliminating those of said previously established response patterns which call for significant signals in those channels in which said formed pattern has no significant signal, and means for processing the remaining ones of said pre-viously established response patterns so as to identify and estimate the concentration of each of said one or more compo-nents in said sample.
sensing means including an array of differently selec-tive sensors, means for introducing to said sensing means a gas sam-ple possibly containing one or more components of a predeter-mined number of components that are detectable by said array, the number of said sensors being greater than one and fewer than said predetermined number, means for forming a multi-channel response pattern from said sensing means upon exposure to said sample, means for comparing said formed pattern with a set of previously established patterns, said comparing means including means for eliminating those of said previously established response patterns which call for significant signals in those channels in which said formed pattern has no significant signal, and means for processing the remaining ones of said pre-viously established response patterns so as to identify and estimate the concentration of each of said one or more compo-nents in said sample.
28. The instrument of Claim 27, and further including means for changing an operational condition of said array to provide a plurality of different responses from each of said sensors, said predetermined number of components being great-er than the product of the number of sensors times the num-ber of different operational conditions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/585,699 US4670405A (en) | 1984-03-02 | 1984-03-02 | Sensor array for toxic gas detection |
| US585,699 | 1984-03-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1237771A true CA1237771A (en) | 1988-06-07 |
Family
ID=24342584
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000474463A Expired CA1237771A (en) | 1984-03-02 | 1985-02-15 | Sensor array for toxic gas detection |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4670405A (en) |
| JP (1) | JPS60205351A (en) |
| CA (1) | CA1237771A (en) |
| DE (1) | DE3507386A1 (en) |
| FR (1) | FR2560684B1 (en) |
| GB (1) | GB2155185B (en) |
| IT (1) | IT1183700B (en) |
Families Citing this family (78)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5106756A (en) * | 1984-03-02 | 1992-04-21 | The United States Of America As Represented By The United States Department Of Energy | Method and system for gathering a library of response patterns for sensor arrays |
| US5047352A (en) * | 1985-05-20 | 1991-09-10 | Arch Development Corporation | Selective chemical detection by energy modulation of sensors |
| US5266270A (en) * | 1985-06-17 | 1993-11-30 | Institut Francais Du Petrole | On-line test and analysis process and equipment making it possible to establish a material balance of a chemical reaction |
| US4866439A (en) * | 1987-03-27 | 1989-09-12 | Kraus John H | Explosives detection system for an aircraft |
| US4847783A (en) * | 1987-05-27 | 1989-07-11 | Richard Grace | Gas sensing instrument |
| DE3729286A1 (en) * | 1987-09-02 | 1989-03-16 | Draegerwerk Ag | MEASURING DEVICE FOR ANALYZING A GAS MIXTURE |
| US5116764A (en) * | 1988-07-26 | 1992-05-26 | Raymond Annino | Dual-column, dual-detector gas detector and analyzer |
| DE3826263A1 (en) * | 1988-08-02 | 1990-02-08 | Siemens Ag | Arrangement for the measurement of the concentrations of components in a gas mixture, using non-selective gas sensors |
| DE3904168A1 (en) * | 1989-02-11 | 1990-08-23 | Honeywell Elac Nautik Gmbh | GAS DETECTOR |
| US5012432A (en) * | 1989-06-13 | 1991-04-30 | Gas Research Institute | Microcalorimeter sensor for the measurement of heat content of natural gas |
| US5071770A (en) * | 1989-09-05 | 1991-12-10 | The United States Of America As Represented By The Secretary Of The Air Force | Method for gaseous component indentification with #3 polymeric film |
| US5045285A (en) * | 1989-09-05 | 1991-09-03 | United States Of America As Represented By The Secretary Of The Air Force | Gaseous component identification with polymeric film sensor |
| US5057436A (en) * | 1989-10-02 | 1991-10-15 | Agmaster, Inc. | Method and apparatus for detecting toxic gases |
| US5286363A (en) * | 1990-10-18 | 1994-02-15 | Georgia-Pacific Resins, Inc. | Dynamic microchamber for measuring formaldehyde emissions |
| DE4136779A1 (en) * | 1991-11-08 | 1993-05-13 | Bayer Ag | DEVICE FOR SIMULTANEOUS DETECTION OF DIFFERENT GAS COMPONENTS |
| US5305231A (en) * | 1992-02-13 | 1994-04-19 | Bacharach, Inc. | Multiple K factor, selectable gas detector |
| US5654497A (en) * | 1992-03-03 | 1997-08-05 | Lockheed Martin Energy Systems, Inc. | Motor vehicle fuel analyzer |
| DE4302367A1 (en) * | 1993-01-28 | 1994-08-04 | Rwe Energie Ag | System for the indirect determination of critical conditions of condition-dependent gases, substances, plant parts etc. |
| US5479359A (en) * | 1993-03-17 | 1995-12-26 | Metcalf & Eddy, Inc. | Automated data collection system for fugitive emission sources |
| DE4311605C1 (en) * | 1993-04-08 | 1994-12-01 | Draegerwerk Ag | Method for determining the proportion of flammable gases in a gas mixture and their classification according to gas class factors |
| GB9318941D0 (en) * | 1993-09-14 | 1993-10-27 | Northumbrian Water Group Plc | Digital control of a mutli sensor system |
| FR2710153B1 (en) * | 1993-09-17 | 1995-12-01 | Alpha Mos Sa | Methods and apparatus for detecting odorous substances and applications. |
| JP2647798B2 (en) * | 1993-12-27 | 1997-08-27 | 工業技術院長 | Chemical / physical quantity identification method and device |
| US5731157A (en) * | 1993-12-30 | 1998-03-24 | The Procter And Gamble Company | Two-site allergen immunoassay |
| US5742516A (en) * | 1994-03-17 | 1998-04-21 | Olcerst; Robert | Indoor air quality and ventilation assessment monitoring device |
| US5526280A (en) * | 1994-04-28 | 1996-06-11 | Atwood Industries, Inc. | Method and system for gas detection |
| DE19509146C1 (en) * | 1995-03-14 | 1996-08-29 | Draegerwerk Ag | Device for the selective detection of a component in a gas mixture |
| US5571401A (en) * | 1995-03-27 | 1996-11-05 | California Institute Of Technology | Sensor arrays for detecting analytes in fluids |
| DE19535071C2 (en) * | 1995-09-21 | 1999-08-19 | Hochtief Ag Hoch Tiefbauten | Process for the non-destructive checking of the position of composite sliding dowels made of ferromagnetic material in a field concrete pavement |
| AU4305396A (en) * | 1995-12-26 | 1997-07-28 | Ingenieria De Los Gases En El Medio Ambiente, S.L. | Digital atmospheric analyser with limited inmission level and regulation of the emission level |
| US5764150A (en) * | 1996-04-10 | 1998-06-09 | Fleury; Byron | Gas alarm |
| US5993743A (en) | 1997-03-26 | 1999-11-30 | Spx Corporation | Hand-held vehicle exhaust analyzer |
| US5987964A (en) * | 1997-03-27 | 1999-11-23 | Simon Fraser University | Apparatus and method for detecting gas and vapor |
| US6076392A (en) * | 1997-08-18 | 2000-06-20 | Metasensors, Inc. | Method and apparatus for real time gas analysis |
| US6079251A (en) * | 1998-02-17 | 2000-06-27 | Noranda Inc. | Diesel exhaust analysis system and method of using the same |
| GB2342171A (en) * | 1998-03-20 | 2000-04-05 | Cyrano Sciences Inc | Handheld sensing apparatus |
| NZ507177A (en) * | 1998-03-20 | 2003-09-26 | Cyrano Sciences Inc | Handheld sensing apparatus with at least two sensors having a common sampling chamber and a microprocessor to analyze sensed response |
| US6085576A (en) | 1998-03-20 | 2000-07-11 | Cyrano Sciences, Inc. | Handheld sensing apparatus |
| US6319724B1 (en) * | 1998-06-19 | 2001-11-20 | Cyrano Sciences, Inc. | Trace level detection of analytes using artificial olfactometry |
| US6095681A (en) * | 1998-07-28 | 2000-08-01 | The United States Of America As Represented By The Secretary Of Commerce | Method for operating a sensor to differentiate between analytes in a sample |
| WO2000050890A1 (en) * | 1999-02-25 | 2000-08-31 | Metasensors, Inc. | Methods and apparatus for real time fluid analysis |
| US7089780B2 (en) * | 1999-03-03 | 2006-08-15 | Smiths Detection Inc. | Apparatus, systems and methods for detecting and transmitting sensory data over a computer network |
| US6837095B2 (en) | 1999-03-03 | 2005-01-04 | Smiths Detection - Pasadena, Inc. | Apparatus, systems and methods for detecting and transmitting sensory data over a computer network |
| WO2000052444A2 (en) | 1999-03-03 | 2000-09-08 | Cyrano Sciences, Inc. | Apparatus, systems and methods for detecting and transmitting sensory data over a computer network |
| US6435007B1 (en) | 1999-05-06 | 2002-08-20 | Sensor Research & Development Corporation | Materials breakthrough monitoring sensor system |
| CA2375516A1 (en) * | 1999-06-17 | 2000-12-28 | Cyrano Sciences, Inc. | Multiple sensing system and device |
| US6182497B1 (en) * | 1999-08-20 | 2001-02-06 | Neodym Systems Inc | Gas detection system and method |
| US6606566B1 (en) * | 1999-11-01 | 2003-08-12 | Steven A. Sunshine | Computer code for portable sensing |
| US6978212B1 (en) | 1999-11-01 | 2005-12-20 | Smiths Detection Inc. | System for portable sensing |
| JP2004523731A (en) * | 2000-10-16 | 2004-08-05 | イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニー | Method and apparatus for analyzing a mixture of gases |
| WO2003050511A1 (en) * | 2001-12-13 | 2003-06-19 | The University Of Wyoming Research Corporation Doing Business As Western Research Institute | Volatile organic compound sensor system |
| US7255677B2 (en) * | 2002-03-04 | 2007-08-14 | Smiths Detection Inc. | Detection, diagnosis, and monitoring of a medical condition or disease with artificial olfactometry |
| US7112447B2 (en) * | 2002-09-27 | 2006-09-26 | Spx Corporation | Hand held gas analyzer |
| US7402284B2 (en) * | 2002-09-27 | 2008-07-22 | Spx Corporation | Orientation device for a gas analyzer |
| US7087434B2 (en) * | 2002-12-20 | 2006-08-08 | Gas Technology Institute | Automatic portable formaldehyde analyzer |
| US6987459B2 (en) * | 2003-01-24 | 2006-01-17 | Honeywell International, Inc. | Portable combustible gas detector |
| US7588726B1 (en) * | 2003-07-11 | 2009-09-15 | Thermo Fisher Scientific Inc. | Vapor analysis apparatus and method |
| JP2005291715A (en) * | 2004-03-31 | 2005-10-20 | Shimadzu Corp | Odor measuring device |
| US7152458B2 (en) * | 2004-11-30 | 2006-12-26 | Honeywell International Inc. | Nano-crystalline and/or metastable metal hydrides as hydrogen source for sensor calibration and self-testing |
| DE102006011117A1 (en) * | 2006-03-08 | 2007-09-13 | Esders Gmbh | Combustible gas detecting device for use in e.g. chemical system, has sensor arranged in measuring space, where value for humidity contained in gas mixture and/or temperature of gas mixture is determined by another sensor |
| US7771654B1 (en) | 2006-09-07 | 2010-08-10 | Moore Randall P | Apparatus for monitoring gaseous components of a flue gas |
| US8721970B2 (en) * | 2008-01-25 | 2014-05-13 | Life Safety Distribution Ag | Temperature and humidity compensated single element pellistor |
| US8087283B2 (en) * | 2008-06-17 | 2012-01-03 | Tricorntech Corporation | Handheld gas analysis systems for point-of-care medical applications |
| CN101692061B (en) * | 2008-07-02 | 2014-05-14 | 孙一慧 | Sensor instrument system including method for detecting analytes in fluids |
| US8999245B2 (en) | 2009-07-07 | 2015-04-07 | Tricorn Tech Corporation | Cascaded gas chromatographs (CGCs) with individual temperature control and gas analysis systems using same |
| US8707760B2 (en) | 2009-07-31 | 2014-04-29 | Tricorntech Corporation | Gas collection and analysis system with front-end and back-end pre-concentrators and moisture removal |
| US8978444B2 (en) | 2010-04-23 | 2015-03-17 | Tricorn Tech Corporation | Gas analyte spectrum sharpening and separation with multi-dimensional micro-GC for gas chromatography analysis |
| US9075029B2 (en) | 2011-01-31 | 2015-07-07 | Scott Technologies, Inc. | System and method for automatically adjusting gas sensor settings and parameters |
| EP2388580A1 (en) * | 2010-05-17 | 2011-11-23 | Airsense Analytics GmbH | Device and method for detecting a reaction product of a hazardous gases generated by an electric discharge |
| EP2388581A1 (en) | 2010-05-17 | 2011-11-23 | Airsense Analytics GmbH | Device and method for detecting dangerous materials comprising at least two replacable sensor elements coupled to an evaluation unit |
| US9927365B2 (en) * | 2011-10-21 | 2018-03-27 | Ag Instruments Ltd. | Gas analysers and a method of making a gas analyser |
| JP2017515093A (en) * | 2014-03-06 | 2017-06-08 | エクストラリス・グローバルＸｔｒａｌｉｓ Ｇｌｏｂａｌ | Multi-channel detector |
| DE102015001084A1 (en) * | 2015-01-30 | 2016-08-04 | Karsten Kotte | Method and device for analyzing, monitoring processes, controlling processes and / or regulating processes |
| CN108139348B (en) | 2015-07-28 | 2021-09-17 | 开利公司 | Refrigerant analyzer and method of use |
| DE102017201680A1 (en) * | 2017-02-02 | 2018-08-02 | bentekk GmbH | Calibration method and measurement and analysis method |
| US10697912B2 (en) | 2017-07-21 | 2020-06-30 | Riken Keiki Co., Ltd. | Gas detection method and gas detector |
| DE102017220114B3 (en) | 2017-11-13 | 2019-05-16 | Robert Bosch Gmbh | Method for operating a gas sensor device and gas sensor device |
| US11054347B1 (en) * | 2019-12-31 | 2021-07-06 | X Development Llc | Enhanced gas sensor selectivity |
Family Cites Families (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2149441A (en) * | 1936-01-11 | 1939-03-07 | Mine Safet Appliances Company | Gas testing method and apparatus |
| US2857251A (en) * | 1953-01-28 | 1958-10-21 | Atlantic Refining Co | Process and dual-detector apparatus for analyzing gases |
| US3695848A (en) * | 1970-04-07 | 1972-10-03 | Naoyoshi Taguchi | Gas detecting device |
| CA915458A (en) * | 1970-07-06 | 1972-11-28 | British Columbia Research Council | Method and apparatus for identifying gases |
| US3830630A (en) * | 1972-06-21 | 1974-08-20 | Triangle Environment Corp | Apparatus and method for alcoholic breath and other gas analysis |
| DE2304464C2 (en) * | 1973-01-31 | 1983-03-10 | Robert Bosch Gmbh, 7000 Stuttgart | Sensor for monitoring the functionality of catalytic converters in exhaust gas |
| GB1474080A (en) * | 1974-07-03 | 1977-05-18 | Nohmi Bosai Kogyo Co Ltd | Gas detector |
| US3997297A (en) * | 1975-03-27 | 1976-12-14 | Anthony Jenkins | Method and apparatus for detecting a constituent in an atmosphere |
| DE2718907C2 (en) * | 1977-04-28 | 1984-04-12 | Robert Bosch Gmbh, 7000 Stuttgart | Sensor for determining the oxygen content in exhaust gases |
| US4169708A (en) * | 1977-06-03 | 1979-10-02 | Muggli Robert Z | Method and apparatus for gas analysis |
| DD138245B1 (en) * | 1978-08-30 | 1980-12-10 | Moebius Hans Heinrich | DEVICE FOR GAS ANALYSIS WITH GALVANIC FIXED TECTROLYTIC CELLS |
| US4225410A (en) * | 1978-12-04 | 1980-09-30 | Technicon Instruments Corporation | Integrated array of electrochemical sensors |
| SU885871A2 (en) * | 1979-08-09 | 1981-11-30 | Киевское Научно-Производственное Объединение "Аналитприбор" | Automatic gas analyzing system |
| US4315753A (en) * | 1980-08-14 | 1982-02-16 | The United States Of America As Represented By The Secretary Of The Interior | Electrochemical apparatus for simultaneously monitoring two gases |
| JPS5766347A (en) * | 1980-10-09 | 1982-04-22 | Hitachi Ltd | Detector for mixture gas |
| US4363635A (en) * | 1981-01-26 | 1982-12-14 | Cal Detect, Inc. | Method and apparatus for measuring breath alcohol |
| JPS589052A (en) * | 1981-07-08 | 1983-01-19 | Nichicon Capacitor Ltd | Detecting element for composition gases |
| JPS5811847A (en) * | 1981-07-16 | 1983-01-22 | Riken Keiki Kk | Background compensation type gas detector |
| GB2105849B (en) * | 1981-09-11 | 1985-05-15 | Coal Ind | Electrical gas analyser for sensing at least two gases |
| US4399684A (en) * | 1981-11-27 | 1983-08-23 | Sierra Monitor Corporation | Gas measurement method |
| JPS58162851A (en) * | 1982-03-24 | 1983-09-27 | Hitachi Ltd | Detecting apparatus of gas |
| US4542640A (en) * | 1983-09-15 | 1985-09-24 | Clifford Paul K | Selective gas detection and measurement system |
-
1984
- 1984-03-02 US US06/585,699 patent/US4670405A/en not_active Expired - Fee Related
-
1985
- 1985-02-14 GB GB08503802A patent/GB2155185B/en not_active Expired
- 1985-02-15 CA CA000474463A patent/CA1237771A/en not_active Expired
- 1985-02-28 JP JP60040239A patent/JPS60205351A/en active Pending
- 1985-02-28 FR FR858502974A patent/FR2560684B1/en not_active Expired - Fee Related
- 1985-03-01 IT IT19720/85A patent/IT1183700B/en active
- 1985-03-02 DE DE19853507386 patent/DE3507386A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB2155185A (en) | 1985-09-18 |
| GB2155185B (en) | 1988-07-20 |
| IT8519720A0 (en) | 1985-03-01 |
| GB8503802D0 (en) | 1985-03-20 |
| JPS60205351A (en) | 1985-10-16 |
| FR2560684B1 (en) | 1990-06-08 |
| IT1183700B (en) | 1987-10-22 |
| FR2560684A1 (en) | 1985-09-06 |
| DE3507386A1 (en) | 1985-09-05 |
| US4670405A (en) | 1987-06-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1237771A (en) | Sensor array for toxic gas detection | |
| US4818348A (en) | Method and apparatus for identifying and quantifying simple and complex chemicals | |
| US4888295A (en) | Portable system and method combining chromatography and array of electrochemical sensors | |
| US6319375B1 (en) | Apparatus for identifying a gas | |
| EP0509171B1 (en) | Method and apparatus for improving the specificity of an ion mobility spectrometer utilizing sulfur dioxide dopant chemistry | |
| US5397442A (en) | Sensor and method for accurately measuring concentrations of oxide compounds in gas mixtures | |
| EP1766384B1 (en) | Gas-monitoring assembly comprising one or more gas sensors and one or more getters, and method of using same | |
| RU2623067C2 (en) | Sensor survey | |
| US6338266B1 (en) | Method of identifying a gas and associated apparatus | |
| GB2288873A (en) | Multi-component gas analysis apparatus | |
| US5683570A (en) | Gas detection method | |
| US7356420B2 (en) | Analyzing system for the detection of reducing and oxidizing gases in a carrier gas with a metal-oxide-semiconductor sensor arrangement | |
| Ashley | Electroanalytical applications in occupational and environmental health | |
| US5429727A (en) | Electrocatalytic cermet gas detector/sensor | |
| CA2395563C (en) | Novel device and method for gas analysis | |
| Sears et al. | Selective thermally cycled gas sensing using fast Fourier-transform techniques | |
| JPH04110651A (en) | Method and equipment for sensing dinitrogen monoxide | |
| CN108139348B (en) | Refrigerant analyzer and method of use | |
| Stetter et al. | Electrochemical determination of hydrazine and methyl-and 1, 1-dimethylhydrazine in air | |
| CA2366909A1 (en) | Device and method for measuring alcohol vapour concentration | |
| Zylka et al. | Rapid dissolved gas analysis by means of electrochemical gas sensors | |
| CA1249334A (en) | Selective chemical detection by energy modulation of sensors | |
| CA2043708C (en) | Method and apparatus for improving the specificity of an ion mobility spectrometer utilizing sulfur dioxide dopant chemistry | |
| RU218460U1 (en) | Electrochemical gas and vapor detector | |
| US3835009A (en) | Fe-1173 electro-chemical sensor and activating method therefor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |