CA1106452A - Telemetric temperature probe for microwave oven - Google Patents
Telemetric temperature probe for microwave ovenInfo
- Publication number
- CA1106452A CA1106452A CA277,600A CA277600A CA1106452A CA 1106452 A CA1106452 A CA 1106452A CA 277600 A CA277600 A CA 277600A CA 1106452 A CA1106452 A CA 1106452A
- Authority
- CA
- Canada
- Prior art keywords
- microwave
- oven
- circuit
- temperature
- signal
- 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
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/6447—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
- H05B6/6467—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using detectors with R.F. transmitters
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J36/00—Parts, details or accessories of cooking-vessels
- A47J36/02—Selection of specific materials, e.g. heavy bottoms with copper inlay or with insulating inlay
- A47J36/027—Cooking- or baking-vessels specially adapted for use in microwave ovens; Accessories therefor
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J36/00—Parts, details or accessories of cooking-vessels
- A47J36/32—Time-controlled igniting mechanisms or alarm devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C7/00—Stoves or ranges heated by electric energy
- F24C7/02—Stoves or ranges heated by electric energy using microwaves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
- G01K1/02—Means for indicating or recording specially adapted for thermometers
- G01K1/024—Means for indicating or recording specially adapted for thermometers for remote indication
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K13/00—Thermometers specially adapted for specific purposes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/32—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using change of resonant frequency of a crystal
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/6447—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
- H05B6/645—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using temperature sensors
- H05B6/6452—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using temperature sensors the sensors being in contact with the heated product
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K2207/00—Application of thermometers in household appliances
- G01K2207/02—Application of thermometers in household appliances for measuring food temperature
- G01K2207/06—Application of thermometers in household appliances for measuring food temperature for preparation purposes
Abstract
MICROWAVE OVEN TEMPERATURE INDICATOR
AND CONTROL MEANS
ABSTRACT OF THE DISCLOSURE
There is disclosed a telemetric temperature probe for telemetry of temperatures of comestibles which are heated within microwave ovens. The probe includes a temperature responsive circuit for generating a signal responsive to the temperature of the comestible and an electromagnetic wave broadcasting circuit for telemetric transmission of the signal to a remote receiver which can conveniently be incorporated in the microwave oven and coupled to its control circuit. The probe is provided with facilities to derive power necessary for its operation from the microwave energy generated by the oven and includes, for this purpose, an antenna to receive microwave energy, a rectifier circuit for developing direct current power therefrom and a voltage regulation circuit to produce a source of direct current of controlled voltage for operation of the temperature responsive circuit and the broadcasting circuit.
AND CONTROL MEANS
ABSTRACT OF THE DISCLOSURE
There is disclosed a telemetric temperature probe for telemetry of temperatures of comestibles which are heated within microwave ovens. The probe includes a temperature responsive circuit for generating a signal responsive to the temperature of the comestible and an electromagnetic wave broadcasting circuit for telemetric transmission of the signal to a remote receiver which can conveniently be incorporated in the microwave oven and coupled to its control circuit. The probe is provided with facilities to derive power necessary for its operation from the microwave energy generated by the oven and includes, for this purpose, an antenna to receive microwave energy, a rectifier circuit for developing direct current power therefrom and a voltage regulation circuit to produce a source of direct current of controlled voltage for operation of the temperature responsive circuit and the broadcasting circuit.
Description
1~06~5~
BACKGROUND OF THE INVENTION
Field of the Invention:
~ This invention relates to a telemetric temperature device and, in particular, to a telemetric temperature probe for microwave processing, typically microwave cooking.
Description of the Prior Art:
Microwave ovens are home appliances of increasîng popularity and sales. The advantages offered by the microwave ovens includes compactness and high thermal efficîencies and speed in cooking. The temperature of comestibles heated in ` the microwave ovens has not, heretofore, been precisely con-trolled because of a lack of precision in detection of temper-atures of comestibles within microwave ovens. Temperature l control is particularly difficult with small size comestibles j~;15~ ~gince the highly efficient microwave oven heats small comes-tibles so rapidly that ordinary timed control of the heating process fails to provide reliable temperature control.
A~number of at~tempts have been made to provide direct measuremen;t~of~temperatures of comestibles within a microwave 0~ oven~ Inc1uded in these~attempts have been positioning of microwave~absorbent material in an internal fixture of the oven~and;mea~suring the temperature of this material, thereby deriving a signal which is proportional to the total energy input~to~the oven. The difficulty with~this approach is that ;¦~ 25~ the~temperature~reached by~a comestLb1e placed within the oven depends on~its mass and condit~ion and only a direct tem~erature measurement~of the comest1b1e is, therefore, reIiable.
Another a~ttempt has been made to provide a thermom-eter~which càn be inserted~into the comestible. The~thexmom-30~ eter is~provided with a non-ionic temperature responsive fluîd ,. :: : :. : :
~: .
.
11~)6~S2 to avoid its interaction ~ith the microwave energy. While this device can be used as a thermometer, it does not provide for automatic control of the microwave oven in response to the sensed temperatures.
Another attempt has been made in which a temperature responsive circuit is positioned within a probe which is coupled through an umbilical cord to the oven control circuit.
The umbilical cord provides the power supply to the temperature responsive circuit and transnits the temperature responsive signal to the oven control circuit. This device is somewhat cumbersome 7 requiring that the probe be inserted and removed from the comestible or disconnected from the oven whenever the comestible is to be placed in or removed from the oven.
SUMMARY OF THE INVENTION
This invention comprises a telemetric temperature probe which can be placed within a comestible to be processed in a microwave oven. The telemetric probe includes power supply means comprising microwave receiver circuit means which ~ includes a microwave receiving antenna, and power control cir-cuit means in circuit therewith to provide a direct current of controlled voltage suitable for driving the telemetric probe circuits. The telemetric probe circuits include a temperature ~responsive circuit that develops a signal which is responsive to the sensed temperature of the comestible and a low fre-quency electromagnetic wave transmission circuit to broadcast the temperature responsive signal. ,, The microwave oven is provided with receiver means `
in~ludîng an antenna for receiving the low frequency broadcast `~ temperature responsive signal and logic circuitry for proces-~;30 sing of the received signal, preferably by digital techniques, ~, : ' - . ,, ,: '.
SZ
to provide an output signal that can be displayed in a conven-tional digital readout or that can be used as an input signal to a digital microprocessor for control of the microwave oven operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described by reference to the figures of which:
Fig. 1 illustrates the temperature probe in a micro-wave oven along a partial sectional view through the microwave cavity;
Fig. 2 is an electrical schematic of an operative circuit for the telemetric temperature probe;
Fig. 3 is asc~ematic of the microwave oven receiver circuit and the data processing facilities;
Fig. 4 illustrates the assembly of the components in a probe ho7~sing; and Fig. 5 is a partial sectional view of the closure end member on the probe housing.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Referring now to Fig. 1, the microwave oven 10 is shown with an outer housing 12 and internal walls to define an oven compartment 14. Typically, the magnetron tube 16 for generating the microwaves is located at the top of the oven, discharging towards wave guide 18 which is formed of microwave reflecting material such as metal, e.g., aluminum, brass, etc., which can have a reflective gold coating.
The wave guide 18 is positioned to reflect the microwaves through the open areas 20 and 22 in the roof 24 of the oven cavity 14. A microwave stirring means in the form of 1106~52 .
a fan 25 is provided in the upper portion of the oven cavity 14 and is slowly rotated by prime mover 26. This stirring means deflects the transmission path of the microwaves passing throu~h apertures 20 and 22 and thereby provides a uniform diffusion of the microwave energy transmitted into the oven cavity 14.
The comestible to be processed, e.g., solid materials such as meat and the like or liquids such as soup and the like, is positioned with the oven cavity 14, typically resting on the bottom floor 30 of the cavity or on a shelf supported within the oven cavity. Comestible 28 is contained within a cooking utensil 32 having a cover 34, both non-metallic. The telemetric temperature probe 36 of the invention is placed at a depth within the comestible 28 sufficient to insure that its temperature sensing portion, e.g., its tip 38, is in heat exchange relationship with the interior of the comestible 28.
The microwave oven 10 includes, in its structure, electromagnetic wave energy receiving means such as the ferrite antenna 40 which is illustrated as mounted near the ventilation apertures 21 of the oven. As shown by partial sectional view A-A, the roof 24 bears apertures 21 forward of the wave guide 18. This location shields antenna ~0 from the microwave energy, yet insures adequate detection sensitivity of the antenna, The microwave oven also includes the conventional facilities such as the on-off switch 52, a door interlock . switch 54 and the transformer and power supply components mounted in housing 55. The power supply cord 56 is connected to terminal block 58 provided with leads such as 6Q that extend to auxiliary equipment such as fans, infrared heater and the like.
Referring now to Fig. 2, the electrical schematic _ 5 _ B
. .
liO~;Z
of a suitable circuit for the telemetric temperature probe is illustrated. This circuit includes a power supply circuit means 62, temperature responsive circuit means 64 and signal broadcasting circuit means 66. These circui~ means are con-tained within the housing of the telemetric temperature probe36 in Fig. l.
The power supply circuit means 62 includes microwave receiver facilities such as loop antenna 70, rectifier circuit means such as diode 72 in circuit with antenna loop 70 and diode 74 in parallel circuit thereto to derive a half wave, direct current, input voltage across capacitor 76.
Due to the variable nature of the microwave energy received by the loop antenna 70, a voltage regulator is util- -ized to provide substantially constant voltage to the temper-lS ature responsive circuit within block 64. The voltage regula-' : tor includes resistors 78 and 80 together with transistor 82 and Zener diode 84 connected in a conventional series voltage regulator configuration whîch provides a substantially con-stant;~D.C. voltage across filter capacitor 86. The generated ~supp~ly~voltage across capacitor 86 powers a commercially available integrated circuit crystal oscillator 88 which :~
provides an oscillator output through a resistor 90 to a tuned circuit~including a capacitor 92 and a ferrite core inductor 94~which also serves as the telemetering transmitting antenna.
25 ~The integrated circuit crystal oscillator 88 utilized in the lllustrat~ed~embodiment is a~commercial unit, No. SQXO-2, ava11able~rom~5tatek Corporation, 1200 Alvarez Ave., Orange, alifornis~9~2668~
The~bas~ic 08cillator frequency is approximately ,~ 3P~ 32,~768~Hertz;~when~operated under normal ambient conditions. It ~ shou~ld~:be~appreciated that the crystal oscillator îs utilized.
:: :
1106~SZ
as the temperature sensin~ device and thus its frequency is variable with temperature as will be described in detail below. The frequency which is broadcast by the inductor antenna 94 is in the very low to low frequencY range. We have ~ 5 found that this frequency range, e.g., from lO,000 to about : 50,000 Hertz, preferably from 25,000 to about 40,000 Hertz, readily penetrates the shielding of the oven which blocks microwave transmission from the oven cavity. Despite the relatively low frequency of the broadcast signal, a sufficiently I0 strong signal can be broadcast with a very compact antenna, thereby providing a very small probe unit. The broadcast, very low to low frequency signal will propagate throughout the oven compartment 14 and through the microwave shielding within , ~ the oven to a receiving antenna as described below.
The telemetering receiver used in illustrated tem-~; perature indicating system of the invention is shown in Fig. 3.
:,~ The ~ery low frequency radio oscillations from the temperature probe transmitter are received by a ferrite loop antenna coil 96 which~form6~s~tuned circuit pickup together with capacitor ,20 ~9~8~:~and~:damping~resistor 100. The received very low to low frequency~energy is transmitted through a shielded cable 102 through capac~itor 104 to the input to an integrated circuit , . :
aud'io~amp1;LfLer 106. The illustrated audio amplifier includes ;,feedback~capacitors 110 and 112 conventionally connected to ~25~ ~the~ampl1f1er 106. The amplifier 106 is available as part L~382'~from National Semiconductor Corporation, Santa Clara, Ca11~ornia~
~ The~output o~f audio amplifier 106 is connected - ~ ~t ~ ùgh~series'capacitor~1~14~and resistor 116 to the primary w m ding~118~of a~conventiona1 and~;com~ercially available in-t~ermed~iate~freguency transfor~er ll9, 19 kHz transformer from ; ~ .
J. W. Miller, Division of Bell Industries, 19070 Reyes ~ve., Compton, California.
The secondary 120 of the transformer 119 forms part of a tuned circuit with capacltor 112 connected ~hrough cap-5 acitor 124 to the input of a phase locked loop oscillator 126.The phase locked loop oscillator 126 is commercially available as #567 from Signetics Corporation, 811 E. Arques Avenue, Sunnyvale, California.
The phase locked loop oscillator 126 is convention-ally compensated by means of capacitors 130 and 132 and timingcompensa~or capacitor 134, resistor 136 and potentiometer 138.
The power supply is connected through resistor 140 and light emitting diode (LED) 142 to the load terminal. The clock out-put of line 144 is substantially a s~uare wave pulse ~ignal corresponding to the oscillator frequency of the probe and serves as the input to the digital circuitry which provides a digital readout of the probe temperature.
When utilizing the integrated circuit crystal oscil-lator 88 in the probe configuration described above, it has been determined that the temperature variable oscillator output changes only one Hertz for every six degrees Fahrenheit change in temperature. Therefore, to detect a change in temperature of one degree Fahrenheit, a sample time equal to approximately six times the number of basic oscillator pulses is required so that the total number of pulses changes by one over the sample time for each degree of temperature change.
To this end, a temperature stable reference oscil-lator 1~6 is provided which feeds a driving transistor 148 to provide pulses on line 1~0 at the same basic rate as those 3Q generated by the oscillator 88 within the probe. The reference oscillator is a conventionally available Model CK-IV ~rom ffff~
Statek Corp., 1200 Alvarez ~venue, Orange, California 92668.
Transistor 148 has a base limiting resistor 152 and a collector resistor 154 in a conven~ional switch configuration. The ref-erence oscillator 146 provides pulses on line 150 of a nominal 32,768 Hertz which are applied to the input of a string of series-connected decade counters 156 through 168. The decade '-~
; counters 156-168 are conventional units in the 54~74 Series of transistor-transistor logic devices available from numerous manufacturers.
The decade counters 156 through 168 count pulses from the reference oscillator 146 until a preset number appears - ~ in the three most significant digit positions of the sample count. As noted above, the number of pulses which are counted is approximately six ~imes the basic oscillator frequency and, : 15 : in the illustrated embodiment, the predetermined number is ' 170,000 which is detected by three BCD-to-decimal decoders 170, 172,~and 174 connected to the outputs of the decade counters 162, 164 and 168 containing the three most significant digits of~the sample count.~ The BCD-to-decimal decoders are also de-` vices~in~the 54/74 Series and readily avaiLable.
When~the;count of 170,000 is decoded, appropriate f~ s'i&nals on~lines 176, 178 and 1;80 are connected'through in-verters~l82,~184, and lfff'6~,~the outputs of which, on lines 188, 190~and~l92,~are connected as inputs to a NAND gate 194 which 25~ generates~;a~sample complete~signal on an output line 196.
Whi~le the~reference osfrillator pulses are being nted by~the~seriès~of~ decade counters 156-168, the probe outpuè;~pulses~on~line~144 a~re being fed to three seri;es- ' ~ -o~nne~cted~up-d~wn decade~counters~198, 200 and 202. The 3`0~ de~fffadé~frou~ters l9f~l~ 200 and 202 are also available as part of~the~54/74 Series.~It~should be appreciated that the up-f ~ 9 ~.. ~, . . ,.. . ,, , ,. , . - ; .
~ 2 down decade counters 198, 200 and 202 will contain only the three least significant digits of the probe frequency, and any number in those decade counters at the completion of the sample time represents a difference in frequency between the probe oscillator and the reference oscillator. As it is desired that the count in the decade counters 198, 200 and 202 at the completion of the sample time represent an actual temperature, a calibration number is preset into the decade counters prior to the beginning of the sample time. Thus, by properly pre-setting the decade counters, at the termination of the sampletime, the number remaining in the decade counters 198, 200 and 202 will be a number indicating actual probe temperature.
In order to display the number in the decade counters 198, 200 and 202, at the completion of the sample time, the sample complete signal on line 196 is fed through an inverter 204 to generate a latch signal on line 206 which is applied to the load inputs of a series of four-bit latches 208, 210 and 212, also from the 54/74 Series, which hold the final number in the decade counters 198, 200 and 202 at the completion of the sample time. The output of the latches 208, 210 and 212 is connected to a series of seven-segment light emitting diode display drivers 214, 216 and 218 which in turn drive three light emitting diode display devices 220, 222 and 224, conven-tionally connected to the drivers through resistors 226. The light emitting diode display devices are conventional units available as part #FND507 from Fairchild Camera & Instrument Corp., Syosset, N. Y, When the number in the decade counters 198, 200 and 202 has been trarlsferred to the latches 208, 210 and 212 by means of the latch signal on line 206, the decade counters must then be reset ~o the predeter~ined calibration number for - : . . . . .
' " ' ' 1 ~0 6~
the ne~t sample time and the sam~le time counters 156-168 must also be reset. This is effected by connecting the sample com-plete signal on line 196 to one of the inputs of each of a pair of NAND gates 228 and 230. The NAND gate 230 is enabled by one of the pulses from the reference oscillator on line 150 which is fed through an inverter 234 to a NAND gate 236 which supplies an enabling input on lîne 238 to the NAND gate 230 which then generates a reset pulse on line 240 connected to the decade counters 156-168. The reset pulse on line 240 also enables the NA~ID gate 228 which then generates a load si~nal on line 242 which causes the predetermined calibration number to be loaded into the up-down decade counters 198, 200 and 202. The next sample time is then evaluated.
Referring to Fig. 4, the temperature probe 36 is shown in partial assembly. The housing 35 is a generally tub-ular member of a non-magnetic corrosion resistant metal such as stainless steel witfi a pointed tip 38 to facilitate insertion - into a comestible.
The electronic components can be assembled in a ~ generally linear array for mounting within the tubular housing :
35. The temperature responsive crystal oscillator 88 is located at a forward position to be carried în the tip 3~ of housing 35, preferably in direct contact therewith, thereby insuring that it will be in a heat exchange position to a comestible receiving the probe 36. The electronic components are secured within tubular housing 35 by collar 39 which has a eleeve 41 that is pressed into the open end 43 of housin~ 35.
The metal walls of housing 35 provide shielding that limits transmission of the microwaves, thereby isolating the , .
electronic components from the microwave energy. If desired, the transmission of the broadcast very low to low requency ; ' ' 1~0~
-temperature modulated signal from ferrite core inductor 94 can be enhanced by reducing the thickness of the wall of housing 35 in region 53 surrounding inductor 94. Alternatively, apertures could be provided in the wall of region 53 and these apertures could be filled or covered with a plastic film for hermetically sealing housing 35. As shown in Fig. 5, the collar 39 has an annular flange 45 which provides a mounting for metal disc 55 which centrally bears a ceramic bushing 57. The bushing 57 has inner and outer metal coatings and is connected in the circuit to provide capacitor 76 shown in Fig. 2. The bushing also provides for passage of wire leads that extend to microwave receiving antennas 70 and 70' (shown in Fig. 4) which are preferably oriented at right angles for maximum reception of microwave energy. Diodes 72 and 74 can also be located outside of housing 35.
The housing is closed with end cap 47 which can be of non-meta1lic construction, ~.g_, formed of Teflon, for maximum reception of microwave energy. The cap 47 fits over collar 39 and seals the interior of housing 35.
Fig. S also illustrates the assembly with collar 39 pressed into end 43 of housing 35 and surrounded by cap 47~
The collar 39 has an annular lip 49 and cap 47 bears an annular groove 51 cooperative therewith to lock the cap to the collar.
Preferably lip 47 is bevelled, as shown, to facilitate seating of cap 47 over collar 39.
The invention has been described with reference to the illustrated, presently preferred embodiment. It is not ntended that the invention be unduly limited by this illustra-tion. Instead, the invention is intended to be defined by the :
~ 30 means~and equivalents thereof set forth in the following claims. ~ ~
.
' ,` ~~ ' ~ ' ' .
BACKGROUND OF THE INVENTION
Field of the Invention:
~ This invention relates to a telemetric temperature device and, in particular, to a telemetric temperature probe for microwave processing, typically microwave cooking.
Description of the Prior Art:
Microwave ovens are home appliances of increasîng popularity and sales. The advantages offered by the microwave ovens includes compactness and high thermal efficîencies and speed in cooking. The temperature of comestibles heated in ` the microwave ovens has not, heretofore, been precisely con-trolled because of a lack of precision in detection of temper-atures of comestibles within microwave ovens. Temperature l control is particularly difficult with small size comestibles j~;15~ ~gince the highly efficient microwave oven heats small comes-tibles so rapidly that ordinary timed control of the heating process fails to provide reliable temperature control.
A~number of at~tempts have been made to provide direct measuremen;t~of~temperatures of comestibles within a microwave 0~ oven~ Inc1uded in these~attempts have been positioning of microwave~absorbent material in an internal fixture of the oven~and;mea~suring the temperature of this material, thereby deriving a signal which is proportional to the total energy input~to~the oven. The difficulty with~this approach is that ;¦~ 25~ the~temperature~reached by~a comestLb1e placed within the oven depends on~its mass and condit~ion and only a direct tem~erature measurement~of the comest1b1e is, therefore, reIiable.
Another a~ttempt has been made to provide a thermom-eter~which càn be inserted~into the comestible. The~thexmom-30~ eter is~provided with a non-ionic temperature responsive fluîd ,. :: : :. : :
~: .
.
11~)6~S2 to avoid its interaction ~ith the microwave energy. While this device can be used as a thermometer, it does not provide for automatic control of the microwave oven in response to the sensed temperatures.
Another attempt has been made in which a temperature responsive circuit is positioned within a probe which is coupled through an umbilical cord to the oven control circuit.
The umbilical cord provides the power supply to the temperature responsive circuit and transnits the temperature responsive signal to the oven control circuit. This device is somewhat cumbersome 7 requiring that the probe be inserted and removed from the comestible or disconnected from the oven whenever the comestible is to be placed in or removed from the oven.
SUMMARY OF THE INVENTION
This invention comprises a telemetric temperature probe which can be placed within a comestible to be processed in a microwave oven. The telemetric probe includes power supply means comprising microwave receiver circuit means which ~ includes a microwave receiving antenna, and power control cir-cuit means in circuit therewith to provide a direct current of controlled voltage suitable for driving the telemetric probe circuits. The telemetric probe circuits include a temperature ~responsive circuit that develops a signal which is responsive to the sensed temperature of the comestible and a low fre-quency electromagnetic wave transmission circuit to broadcast the temperature responsive signal. ,, The microwave oven is provided with receiver means `
in~ludîng an antenna for receiving the low frequency broadcast `~ temperature responsive signal and logic circuitry for proces-~;30 sing of the received signal, preferably by digital techniques, ~, : ' - . ,, ,: '.
SZ
to provide an output signal that can be displayed in a conven-tional digital readout or that can be used as an input signal to a digital microprocessor for control of the microwave oven operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described by reference to the figures of which:
Fig. 1 illustrates the temperature probe in a micro-wave oven along a partial sectional view through the microwave cavity;
Fig. 2 is an electrical schematic of an operative circuit for the telemetric temperature probe;
Fig. 3 is asc~ematic of the microwave oven receiver circuit and the data processing facilities;
Fig. 4 illustrates the assembly of the components in a probe ho7~sing; and Fig. 5 is a partial sectional view of the closure end member on the probe housing.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Referring now to Fig. 1, the microwave oven 10 is shown with an outer housing 12 and internal walls to define an oven compartment 14. Typically, the magnetron tube 16 for generating the microwaves is located at the top of the oven, discharging towards wave guide 18 which is formed of microwave reflecting material such as metal, e.g., aluminum, brass, etc., which can have a reflective gold coating.
The wave guide 18 is positioned to reflect the microwaves through the open areas 20 and 22 in the roof 24 of the oven cavity 14. A microwave stirring means in the form of 1106~52 .
a fan 25 is provided in the upper portion of the oven cavity 14 and is slowly rotated by prime mover 26. This stirring means deflects the transmission path of the microwaves passing throu~h apertures 20 and 22 and thereby provides a uniform diffusion of the microwave energy transmitted into the oven cavity 14.
The comestible to be processed, e.g., solid materials such as meat and the like or liquids such as soup and the like, is positioned with the oven cavity 14, typically resting on the bottom floor 30 of the cavity or on a shelf supported within the oven cavity. Comestible 28 is contained within a cooking utensil 32 having a cover 34, both non-metallic. The telemetric temperature probe 36 of the invention is placed at a depth within the comestible 28 sufficient to insure that its temperature sensing portion, e.g., its tip 38, is in heat exchange relationship with the interior of the comestible 28.
The microwave oven 10 includes, in its structure, electromagnetic wave energy receiving means such as the ferrite antenna 40 which is illustrated as mounted near the ventilation apertures 21 of the oven. As shown by partial sectional view A-A, the roof 24 bears apertures 21 forward of the wave guide 18. This location shields antenna ~0 from the microwave energy, yet insures adequate detection sensitivity of the antenna, The microwave oven also includes the conventional facilities such as the on-off switch 52, a door interlock . switch 54 and the transformer and power supply components mounted in housing 55. The power supply cord 56 is connected to terminal block 58 provided with leads such as 6Q that extend to auxiliary equipment such as fans, infrared heater and the like.
Referring now to Fig. 2, the electrical schematic _ 5 _ B
. .
liO~;Z
of a suitable circuit for the telemetric temperature probe is illustrated. This circuit includes a power supply circuit means 62, temperature responsive circuit means 64 and signal broadcasting circuit means 66. These circui~ means are con-tained within the housing of the telemetric temperature probe36 in Fig. l.
The power supply circuit means 62 includes microwave receiver facilities such as loop antenna 70, rectifier circuit means such as diode 72 in circuit with antenna loop 70 and diode 74 in parallel circuit thereto to derive a half wave, direct current, input voltage across capacitor 76.
Due to the variable nature of the microwave energy received by the loop antenna 70, a voltage regulator is util- -ized to provide substantially constant voltage to the temper-lS ature responsive circuit within block 64. The voltage regula-' : tor includes resistors 78 and 80 together with transistor 82 and Zener diode 84 connected in a conventional series voltage regulator configuration whîch provides a substantially con-stant;~D.C. voltage across filter capacitor 86. The generated ~supp~ly~voltage across capacitor 86 powers a commercially available integrated circuit crystal oscillator 88 which :~
provides an oscillator output through a resistor 90 to a tuned circuit~including a capacitor 92 and a ferrite core inductor 94~which also serves as the telemetering transmitting antenna.
25 ~The integrated circuit crystal oscillator 88 utilized in the lllustrat~ed~embodiment is a~commercial unit, No. SQXO-2, ava11able~rom~5tatek Corporation, 1200 Alvarez Ave., Orange, alifornis~9~2668~
The~bas~ic 08cillator frequency is approximately ,~ 3P~ 32,~768~Hertz;~when~operated under normal ambient conditions. It ~ shou~ld~:be~appreciated that the crystal oscillator îs utilized.
:: :
1106~SZ
as the temperature sensin~ device and thus its frequency is variable with temperature as will be described in detail below. The frequency which is broadcast by the inductor antenna 94 is in the very low to low frequencY range. We have ~ 5 found that this frequency range, e.g., from lO,000 to about : 50,000 Hertz, preferably from 25,000 to about 40,000 Hertz, readily penetrates the shielding of the oven which blocks microwave transmission from the oven cavity. Despite the relatively low frequency of the broadcast signal, a sufficiently I0 strong signal can be broadcast with a very compact antenna, thereby providing a very small probe unit. The broadcast, very low to low frequency signal will propagate throughout the oven compartment 14 and through the microwave shielding within , ~ the oven to a receiving antenna as described below.
The telemetering receiver used in illustrated tem-~; perature indicating system of the invention is shown in Fig. 3.
:,~ The ~ery low frequency radio oscillations from the temperature probe transmitter are received by a ferrite loop antenna coil 96 which~form6~s~tuned circuit pickup together with capacitor ,20 ~9~8~:~and~:damping~resistor 100. The received very low to low frequency~energy is transmitted through a shielded cable 102 through capac~itor 104 to the input to an integrated circuit , . :
aud'io~amp1;LfLer 106. The illustrated audio amplifier includes ;,feedback~capacitors 110 and 112 conventionally connected to ~25~ ~the~ampl1f1er 106. The amplifier 106 is available as part L~382'~from National Semiconductor Corporation, Santa Clara, Ca11~ornia~
~ The~output o~f audio amplifier 106 is connected - ~ ~t ~ ùgh~series'capacitor~1~14~and resistor 116 to the primary w m ding~118~of a~conventiona1 and~;com~ercially available in-t~ermed~iate~freguency transfor~er ll9, 19 kHz transformer from ; ~ .
J. W. Miller, Division of Bell Industries, 19070 Reyes ~ve., Compton, California.
The secondary 120 of the transformer 119 forms part of a tuned circuit with capacltor 112 connected ~hrough cap-5 acitor 124 to the input of a phase locked loop oscillator 126.The phase locked loop oscillator 126 is commercially available as #567 from Signetics Corporation, 811 E. Arques Avenue, Sunnyvale, California.
The phase locked loop oscillator 126 is convention-ally compensated by means of capacitors 130 and 132 and timingcompensa~or capacitor 134, resistor 136 and potentiometer 138.
The power supply is connected through resistor 140 and light emitting diode (LED) 142 to the load terminal. The clock out-put of line 144 is substantially a s~uare wave pulse ~ignal corresponding to the oscillator frequency of the probe and serves as the input to the digital circuitry which provides a digital readout of the probe temperature.
When utilizing the integrated circuit crystal oscil-lator 88 in the probe configuration described above, it has been determined that the temperature variable oscillator output changes only one Hertz for every six degrees Fahrenheit change in temperature. Therefore, to detect a change in temperature of one degree Fahrenheit, a sample time equal to approximately six times the number of basic oscillator pulses is required so that the total number of pulses changes by one over the sample time for each degree of temperature change.
To this end, a temperature stable reference oscil-lator 1~6 is provided which feeds a driving transistor 148 to provide pulses on line 1~0 at the same basic rate as those 3Q generated by the oscillator 88 within the probe. The reference oscillator is a conventionally available Model CK-IV ~rom ffff~
Statek Corp., 1200 Alvarez ~venue, Orange, California 92668.
Transistor 148 has a base limiting resistor 152 and a collector resistor 154 in a conven~ional switch configuration. The ref-erence oscillator 146 provides pulses on line 150 of a nominal 32,768 Hertz which are applied to the input of a string of series-connected decade counters 156 through 168. The decade '-~
; counters 156-168 are conventional units in the 54~74 Series of transistor-transistor logic devices available from numerous manufacturers.
The decade counters 156 through 168 count pulses from the reference oscillator 146 until a preset number appears - ~ in the three most significant digit positions of the sample count. As noted above, the number of pulses which are counted is approximately six ~imes the basic oscillator frequency and, : 15 : in the illustrated embodiment, the predetermined number is ' 170,000 which is detected by three BCD-to-decimal decoders 170, 172,~and 174 connected to the outputs of the decade counters 162, 164 and 168 containing the three most significant digits of~the sample count.~ The BCD-to-decimal decoders are also de-` vices~in~the 54/74 Series and readily avaiLable.
When~the;count of 170,000 is decoded, appropriate f~ s'i&nals on~lines 176, 178 and 1;80 are connected'through in-verters~l82,~184, and lfff'6~,~the outputs of which, on lines 188, 190~and~l92,~are connected as inputs to a NAND gate 194 which 25~ generates~;a~sample complete~signal on an output line 196.
Whi~le the~reference osfrillator pulses are being nted by~the~seriès~of~ decade counters 156-168, the probe outpuè;~pulses~on~line~144 a~re being fed to three seri;es- ' ~ -o~nne~cted~up-d~wn decade~counters~198, 200 and 202. The 3`0~ de~fffadé~frou~ters l9f~l~ 200 and 202 are also available as part of~the~54/74 Series.~It~should be appreciated that the up-f ~ 9 ~.. ~, . . ,.. . ,, , ,. , . - ; .
~ 2 down decade counters 198, 200 and 202 will contain only the three least significant digits of the probe frequency, and any number in those decade counters at the completion of the sample time represents a difference in frequency between the probe oscillator and the reference oscillator. As it is desired that the count in the decade counters 198, 200 and 202 at the completion of the sample time represent an actual temperature, a calibration number is preset into the decade counters prior to the beginning of the sample time. Thus, by properly pre-setting the decade counters, at the termination of the sampletime, the number remaining in the decade counters 198, 200 and 202 will be a number indicating actual probe temperature.
In order to display the number in the decade counters 198, 200 and 202, at the completion of the sample time, the sample complete signal on line 196 is fed through an inverter 204 to generate a latch signal on line 206 which is applied to the load inputs of a series of four-bit latches 208, 210 and 212, also from the 54/74 Series, which hold the final number in the decade counters 198, 200 and 202 at the completion of the sample time. The output of the latches 208, 210 and 212 is connected to a series of seven-segment light emitting diode display drivers 214, 216 and 218 which in turn drive three light emitting diode display devices 220, 222 and 224, conven-tionally connected to the drivers through resistors 226. The light emitting diode display devices are conventional units available as part #FND507 from Fairchild Camera & Instrument Corp., Syosset, N. Y, When the number in the decade counters 198, 200 and 202 has been trarlsferred to the latches 208, 210 and 212 by means of the latch signal on line 206, the decade counters must then be reset ~o the predeter~ined calibration number for - : . . . . .
' " ' ' 1 ~0 6~
the ne~t sample time and the sam~le time counters 156-168 must also be reset. This is effected by connecting the sample com-plete signal on line 196 to one of the inputs of each of a pair of NAND gates 228 and 230. The NAND gate 230 is enabled by one of the pulses from the reference oscillator on line 150 which is fed through an inverter 234 to a NAND gate 236 which supplies an enabling input on lîne 238 to the NAND gate 230 which then generates a reset pulse on line 240 connected to the decade counters 156-168. The reset pulse on line 240 also enables the NA~ID gate 228 which then generates a load si~nal on line 242 which causes the predetermined calibration number to be loaded into the up-down decade counters 198, 200 and 202. The next sample time is then evaluated.
Referring to Fig. 4, the temperature probe 36 is shown in partial assembly. The housing 35 is a generally tub-ular member of a non-magnetic corrosion resistant metal such as stainless steel witfi a pointed tip 38 to facilitate insertion - into a comestible.
The electronic components can be assembled in a ~ generally linear array for mounting within the tubular housing :
35. The temperature responsive crystal oscillator 88 is located at a forward position to be carried în the tip 3~ of housing 35, preferably in direct contact therewith, thereby insuring that it will be in a heat exchange position to a comestible receiving the probe 36. The electronic components are secured within tubular housing 35 by collar 39 which has a eleeve 41 that is pressed into the open end 43 of housin~ 35.
The metal walls of housing 35 provide shielding that limits transmission of the microwaves, thereby isolating the , .
electronic components from the microwave energy. If desired, the transmission of the broadcast very low to low requency ; ' ' 1~0~
-temperature modulated signal from ferrite core inductor 94 can be enhanced by reducing the thickness of the wall of housing 35 in region 53 surrounding inductor 94. Alternatively, apertures could be provided in the wall of region 53 and these apertures could be filled or covered with a plastic film for hermetically sealing housing 35. As shown in Fig. 5, the collar 39 has an annular flange 45 which provides a mounting for metal disc 55 which centrally bears a ceramic bushing 57. The bushing 57 has inner and outer metal coatings and is connected in the circuit to provide capacitor 76 shown in Fig. 2. The bushing also provides for passage of wire leads that extend to microwave receiving antennas 70 and 70' (shown in Fig. 4) which are preferably oriented at right angles for maximum reception of microwave energy. Diodes 72 and 74 can also be located outside of housing 35.
The housing is closed with end cap 47 which can be of non-meta1lic construction, ~.g_, formed of Teflon, for maximum reception of microwave energy. The cap 47 fits over collar 39 and seals the interior of housing 35.
Fig. S also illustrates the assembly with collar 39 pressed into end 43 of housing 35 and surrounded by cap 47~
The collar 39 has an annular lip 49 and cap 47 bears an annular groove 51 cooperative therewith to lock the cap to the collar.
Preferably lip 47 is bevelled, as shown, to facilitate seating of cap 47 over collar 39.
The invention has been described with reference to the illustrated, presently preferred embodiment. It is not ntended that the invention be unduly limited by this illustra-tion. Instead, the invention is intended to be defined by the :
~ 30 means~and equivalents thereof set forth in the following claims. ~ ~
.
' ,` ~~ ' ~ ' ' .
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A telemetric temperature probe for determining the temperature of a comestible placed within a microwave oven including:
microwave receiver circuit means;
power supply circuit means in circuit with said microwave receiver circuit means to generate a power supply from received microwave radiation;
temperature sensitive means carried by said probe in heat exchanging relationship to said comestible;
oscillator circuit means driven by said power supply circuit means to generate an oscillatory signal modulated by said temperature sensitive means and of a frequency distinct from said microwave frequency;
electromagnetic wave transmission means to broadcast said oscillatory signal; and a probe housing for insertion in a comestible placed within said oven and having shielding means (metal walls of housing) surrounding said power supply means, oscillator circuit means and wave transmission means of selective permeability to limit transmission of microwave energy while permitting trans-mission of said broadcast oscillatory signal.
microwave receiver circuit means;
power supply circuit means in circuit with said microwave receiver circuit means to generate a power supply from received microwave radiation;
temperature sensitive means carried by said probe in heat exchanging relationship to said comestible;
oscillator circuit means driven by said power supply circuit means to generate an oscillatory signal modulated by said temperature sensitive means and of a frequency distinct from said microwave frequency;
electromagnetic wave transmission means to broadcast said oscillatory signal; and a probe housing for insertion in a comestible placed within said oven and having shielding means (metal walls of housing) surrounding said power supply means, oscillator circuit means and wave transmission means of selective permeability to limit transmission of microwave energy while permitting trans-mission of said broadcast oscillatory signal.
2. The combination of a microwave oven and the tel-emetric temperature probe of Claim 1 also including:
a microwave oven housing having internal walls de-fining and providing microwave shielding about an oven cavity;
signal receiver means mounted in said oven to receive said broadcast oscillatory signal; and shielding means, of selective permeability to limit transmission of microwave energy while permitting transmission of said broadcast oscillatory signal, in said oven and surround-ing said signal receiver means.
a microwave oven housing having internal walls de-fining and providing microwave shielding about an oven cavity;
signal receiver means mounted in said oven to receive said broadcast oscillatory signal; and shielding means, of selective permeability to limit transmission of microwave energy while permitting transmission of said broadcast oscillatory signal, in said oven and surround-ing said signal receiver means.
3. The combination of Claim 1 including signal pro-cessing means connected to visual temperature display means.
4. The combination of Claim 1 wherein said microwave oven includes a digital microprocessor operatively connected to oven control means including signal processing means to provide a digital control signal and means to input said digital control signal to said microprocessor.
5. The combination of Claim 1 wherein said oscil-lator circuit generates an oscillatory signal having a frequency from 10,000 to about 50,000 Hertz.
6. The combination of Claim 1 wherein said power supply circuit means includes rectifier circuit means to develop a D.C. power supply from received microwave energy and a voltage regulation means to maintain a constant predetermined voltage of said D.C. power supply.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/682,198 US4297557A (en) | 1976-05-03 | 1976-05-03 | Microwave oven temperature indicator and control means |
| US682,198 | 1976-05-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106452A true CA1106452A (en) | 1981-08-04 |
Family
ID=24738649
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA277,600A Expired CA1106452A (en) | 1976-05-03 | 1977-05-02 | Telemetric temperature probe for microwave oven |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4297557A (en) |
| JP (1) | JPS52134461A (en) |
| CA (1) | CA1106452A (en) |
| DE (1) | DE2719588A1 (en) |
| GB (1) | GB1530217A (en) |
| SE (1) | SE7704932L (en) |
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| JPS592156B2 (en) * | 1976-11-25 | 1984-01-17 | 松下電器産業株式会社 | High frequency heating device |
| JPS53101144A (en) * | 1977-02-15 | 1978-09-04 | Matsushita Electric Ind Co Ltd | High frequency heating apparatus |
| JPS5823715B2 (en) * | 1977-03-16 | 1983-05-17 | 松下電器産業株式会社 | High frequency heating device |
| JPS59954B2 (en) * | 1977-04-20 | 1984-01-09 | 松下電器産業株式会社 | High frequency heating device |
| JPS54134479A (en) * | 1978-04-10 | 1979-10-18 | Sharp Corp | Wireless temperature measuring device |
| US4377733A (en) * | 1978-08-31 | 1983-03-22 | Sharp Kabushiki Kaisha | Temperature-sensing probe structure for wireless temperature-sensing system |
| US4340796A (en) * | 1978-08-31 | 1982-07-20 | Sharp Kabushiki Kaisha | Wireless temperature-sensing system inclusive of thermally-responsive oscillator |
| JPS5688294A (en) * | 1979-12-21 | 1981-07-17 | Tokyo Shibaura Electric Co | Electronic range |
| JPS578416U (en) * | 1980-06-17 | 1982-01-16 | ||
| DE3219558C2 (en) * | 1982-05-25 | 1986-10-23 | Norbert H.L. Dr.-Ing. 5173 Aldenhoven Koster | Device for determining the local temperature in living tissue |
| FR2535833A1 (en) * | 1982-11-08 | 1984-05-11 | Levalois Daniel | Domestic or kitchen system intended for regulating means for heating the contents of a container. |
| US4685047A (en) * | 1986-07-16 | 1987-08-04 | Phillips Raymond P Sr | Apparatus for converting radio frequency energy to direct current |
| US5320804A (en) * | 1989-05-15 | 1994-06-14 | Cem Corporation | Process and apparatus for controlled microwave heating under pressure |
| JP2797657B2 (en) * | 1990-06-01 | 1998-09-17 | 松下電器産業株式会社 | High frequency heating equipment |
| IL109502A (en) * | 1994-05-02 | 1996-09-12 | Target Custom Made Software An | Control system for domestic water tank |
| DE4421373A1 (en) * | 1994-06-18 | 1995-12-21 | Wiesheu Wiwa Gmbh | Oven for the heat treatment of lumpy foods |
| USH1744H (en) * | 1995-09-21 | 1998-08-04 | Clayton; Stanley R. | Wireless remote sensing thermometer |
| AU4169099A (en) * | 1998-06-19 | 2000-01-05 | Matsushita Electric Industrial Co., Ltd. | Data transmitting/receiving method and device, and program recorded medium |
| US7075442B2 (en) * | 2003-07-07 | 2006-07-11 | Mastrad Sa | Food temperature monitoring device |
| DE102004013621A1 (en) * | 2004-03-19 | 2005-10-06 | BSH Bosch und Siemens Hausgeräte GmbH | Remote monitoring system for steamer and parts thereof |
| DE102004047756B4 (en) * | 2004-09-30 | 2012-03-01 | BSH Bosch und Siemens Hausgeräte GmbH | Temperature sensor device |
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| US8569050B1 (en) * | 2009-05-04 | 2013-10-29 | John D. Ericsson | Enclosed bioreactor system and methods associated therewith |
| AU2010268197A1 (en) * | 2009-07-03 | 2012-01-19 | Nestec S.A. | Capsule for the preparation of a beverage embedding an identification element |
| DE102010062162A1 (en) * | 2010-11-30 | 2012-05-31 | BSH Bosch und Siemens Hausgeräte GmbH | Household microwave oven, implement and method of reading data |
| KR20140058646A (en) | 2011-08-31 | 2014-05-14 | 고지 엘티디. | Object processing state sensing using rf radiation |
| EP2807902B1 (en) * | 2012-01-23 | 2020-08-19 | CONNORS, Robert W. | Compact microwave oven |
| WO2016162499A1 (en) * | 2015-04-10 | 2016-10-13 | Danmarks Tekniske Universitet | Medical preparation container comprising microwave powered sensor assembly |
| US11946812B2 (en) * | 2015-06-25 | 2024-04-02 | Apption Labs Limited | Food thermometer and method of using thereof |
| US11506545B2 (en) * | 2015-06-25 | 2022-11-22 | Apption Labs Limited | Food thermometer and method of using thereof |
| EP3722761B1 (en) | 2015-06-25 | 2023-06-07 | Apption Labs Ltd. | Method of using a food thermometer |
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| EP3308683B1 (en) * | 2016-10-11 | 2020-07-01 | Electrolux Appliances Aktiebolag | Cooking vessel for an oven cavity of a cooking oven |
| KR20190062528A (en) * | 2016-10-12 | 2019-06-05 | 덴마크스 텍니스케 유니버시테트 | Sensor assembly for microwave oven cooking chamber and method of controlling energy consumption of such sensor assembly |
| FI127116B (en) * | 2016-12-02 | 2017-11-30 | Wiciot Oy | Protective cover and measuring system |
| US11056763B2 (en) | 2017-06-01 | 2021-07-06 | Apption Labs Limited | Wireless communication improvements for cooking appliances |
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| CN114980360A (en) * | 2021-04-23 | 2022-08-30 | 深圳市安服优智能互联科技有限公司 | Wireless low-frequency communication method and system |
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| US2813242A (en) * | 1954-03-12 | 1957-11-12 | Lloyd R Crump | Powering electrical devices with energy abstracted from the atmosphere |
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| US3434678A (en) * | 1965-05-05 | 1969-03-25 | Raytheon Co | Microwave to dc converter |
| US3582921A (en) * | 1968-08-06 | 1971-06-01 | Charles R Krieger | Temperature transducer and telemetry system |
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| US3872728A (en) * | 1972-10-10 | 1975-03-25 | Michael F Joyce | Electronic temperature measuring instrument |
| US4001798A (en) * | 1975-09-18 | 1977-01-04 | Rockwell International Corporation | Self-contained sensor |
| US3988929A (en) * | 1975-12-22 | 1976-11-02 | General Electric Company | Handle and reflector assembly for microwave oven food temperature sensing probe |
-
1976
- 1976-05-03 US US05/682,198 patent/US4297557A/en not_active Expired - Lifetime
-
1977
- 1977-04-28 SE SE7704932A patent/SE7704932L/en unknown
- 1977-05-02 CA CA277,600A patent/CA1106452A/en not_active Expired
- 1977-05-02 DE DE19772719588 patent/DE2719588A1/en not_active Withdrawn
- 1977-05-02 GB GB18281/77A patent/GB1530217A/en not_active Expired
- 1977-05-02 JP JP5112477A patent/JPS52134461A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2719588A1 (en) | 1977-11-17 |
| SE7704932L (en) | 1977-11-04 |
| JPS52134461A (en) | 1977-11-10 |
| GB1530217A (en) | 1978-10-25 |
| US4297557A (en) | 1981-10-27 |
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