US20070044708A1 - Ultrasonic sensor assembly and method - Google Patents
Ultrasonic sensor assembly and method Download PDFInfo
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- US20070044708A1 US20070044708A1 US11/213,221 US21322105A US2007044708A1 US 20070044708 A1 US20070044708 A1 US 20070044708A1 US 21322105 A US21322105 A US 21322105A US 2007044708 A1 US2007044708 A1 US 2007044708A1
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- Prior art keywords
- crystal
- circuit board
- transducer
- leg
- circuit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2968—Transducers specially adapted for acoustic level indicators
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2961—Acoustic waves for discrete levels
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
- Y10T117/10—Apparatus
- Y10T117/1004—Apparatus with means for measuring, testing, or sensing
Definitions
- This invention relates to an ultrasonic point level measurement instrument and, more particularly, to an improved transducer and method of assembling a transducer.
- Level measurement instruments may provide a continuous signal indicating level of the material in a tank or vessel, or may comprise point level measurement instruments that indicate the presence or absence of the material at a discrete level in the tank or vessel.
- Ultrasonic level measurement instruments are designed for non-contact sensing or contact sensing. Contact liquid level sensing for point measurement is achieved by using continuous-wave or pulse-signal technology.
- Continuous-wave instruments have two piezoelectric crystals mounted opposite each other in a transducer body, separated by a gap.
- the transmit crystal produces an acoustical signal when subjected to an implied voltage from an amplifier circuit.
- the receive crystal converts the acoustical signal that it receives into an electrical signal, which becomes the input of the same amplifier circuit.
- the amplifier becomes an oscillator causing a relay circuit in the electronics to indicate a wet gap condition.
- the amplifier returns to an idle state.
- a digital electronic amplifier produces a powerful pulse of ultrasonic energy more powerful than with most continuous-wave instruments. This allows measurement in conditions that include aeration, suspended solids, turbulence, and highly viscous liquids. Pulses of high-frequency ultrasonic energy milliseconds in duration are produced by the transmit crystal. In between each pulse, the receive crystal “listens” for the transmission. If liquid is present in the gap, the receive crystal detects the pulse and reports a wet gap condition to the electronics. When the gap is filled with air, the receive crystal cannot detect a pulse and reports a dry gap condition.
- a transducer in one known form sometimes referred to as tip-sensitive style, includes a housing with a pair of spaced apart legs to define a gap therebetween.
- Piezoelectric crystal assemblies that form the sensor drive and receive elements are hand assembled. They must have a plurality of spacers glued to one of the crystal surfaces to provide proper positioning. Wires must be attached to each side of the crystal for electrical connection. Electrical insulating spacers are placed inside the transducer housing. After the two crystal assemblies are placed in the sensor tip, the sensor assembly is potted. Thereafter, coaxial cables must be attached to the crystal wires, as by splicing. Thereafter, the electrical connections must be potted. This manual process can be time consuming. Also, there can be lack of uniformity in construction of the crystal assemblies and thus the sensor assembly.
- the present invention is directed to improvements in ultrasonic sensor assembly.
- an improvement in an ultrasonic point level measurement instrument comprising a measurement circuit and a transducer.
- the transducer transmits and receives acoustic signals under control of the measurement circuit.
- the improvement comprises a transducer housing including a pair of spaced apart legs to define a gap therebetween. Each leg includes an interior cavity.
- a pair of crystal assemblies each comprise a crystal mounted to a circuit board.
- the circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg.
- a pair of cables are each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
- each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board.
- Each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.
- each circuit board insulates one side of the crystal from the walls of the leg and an insulating spacer insulates another side of the crystal from the walls of the leg.
- the insulating spacer biases the circuit board against one of the walls of the leg.
- the interior cavities are encapsulated with a compound, such as an epoxy.
- a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit.
- the transducer transmits and receives acoustic signals under control of the measurement circuit.
- the transducer comprises a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body.
- the legs are generally semi-cylindrical with facing planar walls to define a gap therebetween.
- Each leg includes an interior cavity opening into the body.
- a pair of crystal assemblies each comprise a crystal mounted to a circuit board.
- the circuit board includes conduction paths for connection between the crystal and a terminal pad.
- Each crystal assembly is received in the interior cavity of one of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall.
- a pair of cables is each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
- the method of assembling a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer for transmitting and receiving acoustic signals under control of the measurement circuit, comprising: providing a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body; assembling a plurality of crystal assemblies, for each comprising mounting a crystal to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad; inserting a crystal assembly in the interior cavity of each of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and electrically connecting a cable between the measurement circuit and the terminal pad of each of the crystal assemblies so that the measurement circuit can detect presence of a material in the gap.
- FIG. 1 is a side elevation view of an ultrasonic point level measurement instrument including an ultrasonic sensor assembly in accordance with the invention
- FIG. 2 is a side elevation view of the ultrasonic sensor assembly in accordance with the invention removed from the instrument of FIG. 1 ;
- FIG. 3 is a top plan view of the ultrasonic sensor assembly of FIG. 2 ;
- FIG. 4 is a sectional view taken along the line 4 - 4 of FIG. 2 ;
- FIG. 5 is a sectional view taken along the line 5 - 5 of FIG. 4 specifically illustrating a crystal circuit assembly with other parts removed for clarity;
- FIG. 6 is a schematic/block diagram of the point level measurement instrument of FIG. 1 .
- the process instrument 10 uses ultrasound technology for measuring point level. Particularly, an acoustic signal is transmitted between crystals to detect presence or absence of a material in a gap.
- the process instrument 10 includes a control housing 12 , a transducer 14 and an extension rod 16 connecting the transducer 14 to the control housing 12 .
- the extension rod 16 may include a threaded fitting 18 for connection to a process vessel. Alternatively, a flange or other structure may be used.
- the control housing 12 houses a measurement circuit 20 , see FIG. 6 .
- the measurement circuit 20 is electrically connected, as described more particularly below, to a sensor assembly in the form of the transducer 14 .
- a less expensive and more consistent process is used for producing the transducer 14 .
- the transducer, i.e., sensor assembly, 14 includes a metal housing 22 , a pair of crystal assemblies 24 A and 24 B, and a pair of cables 26 A and 26 B electrically connecting the respective crystal assemblies 24 A and 24 B to the measurement circuit 20 , see FIG. 6 .
- the housing 22 includes a generally cylindrical body 28 with a pair of spaced apart legs 30 A and 30 B extending from the body 28 .
- the legs 30 A and 30 B are generally semi-cylindrical.
- the first leg 30 A comprises a semi-cylindrical wall 32 A connected to a planar wall 34 A.
- the second leg 30 B includes a semi-cylindrical wall 32 B connected to a planar wall 34 B.
- a distal end of each leg 30 A and 30 B is closed by a respective bottom wall 36 A and 36 B.
- Each leg includes an interior cavity 38 A and 38 B opening to an interior space 40 of the body 28 .
- the radius of the semi-cylindrical walls 32 A and 32 B correspond to that of the body 28 to provide a continuous, seamless construction, as is particularly apparent in FIG. 4 .
- Upper ends of the planar walls 34 A and 34 B are connected by a bridge wall 42 .
- the planar walls 34 A and 34 B face one another to define a gap G therebetween.
- the transducer housing 22 can be formed of various materials such as, for example, stainless steel. The particular material used for the housing 22 does not itself form part of the invention. Moreover, while the housing 22 is illustrated as being cylindrical with generally semi-cylindrical legs, other constructions can be used to form a gap.
- a crystal assembly 24 is illustrated.
- the crystal surface 24 A and 24 B discussed above, are identical in construction. For simplicity, they are described generically relative to FIG. 5 and omitting the suffix A or B.
- the crystal assembly 24 includes a printed circuit board 50 .
- the printed circuit board includes conductive crystal pads 52 and terminal pads 54 .
- the printed circuit board 50 is made of an insulating material.
- the circuit board 50 has various conduction traces or paths on either side and some covered by insulating layers and the like.
- FIG. 5 does not specifically illustrate the conductive paths.
- the conductive paths connect the crystal pads 52 and the terminal pads 54 and other devices as illustrated schematically in FIG. 6 , discussed below. Where the paths are located and how they are traced on the printed circuit board 50 is generally a matter of choice.
- a crystal 56 is generally planar and include opposite first and second conductive surfaces 58 and 60 , respectively, see also FIG. 6 .
- the first conductive surface 58 contacts the crystal pads 52 so that the second conductive surface 60 faces away from the circuit board 50 , as shown in FIG. 5 .
- a two pin connector 62 is electrically connected between the second conductive surface 60 and the board 50 .
- a resistor 64 is also mounted to the circuit board 50 .
- Surface flow soldering is used to provide connections between the devices 56 , 62 and 64 and the circuit board 50 , with the connections from the connector 62 to the crystal second conductive surface 60 being made by soldering or the like.
- the terminal pad 54 is electrically connected to the coaxial cable 26 by soldering a center conductor 66 to one of the terminal pads 54 , and using a jumper 68 to connect a coaxial cable shield 69 to the other terminal pad 54 .
- the shield 69 serves as a ground.
- the center conductor 66 is electrically connected from the terminal pad 54 to one pin of the connector 62 to the crystal second conductive surface 60 .
- the other pin of the connector 62 is connected to one side of the resistor 64 .
- the resistor 64 may be, for example, a 10K resistor which can be used for testing or other purposes.
- the other side of the resistor 64 is electrically connected to the crystal pads 52 which are soldered to the crystal first conductive surface 58 .
- the crystal pads 52 are also electrically connected to the cable shield 68 .
- the crystal 56 is approximately 3 ⁇ 8′′ square and 0.040′′ thick.
- a conductive coating is placed on the opposite planar surfaces.
- the first conductive surface 58 makes contact with the terminal pads 52.
- the second conductive surface 60 makes contact with the connector 62.
- the circuit board 50 includes a generally square shaped opening 70 disposed between the four crystal pads 52 and thus beneath the crystal 56.
- the process or method for assembling the transducer 22 is now described.
- one housing 22 and two crystal assemblies 24 A and 24 B are used, along with two cables 26 A and 26 B.
- a contact cement or rubber cement is spread on the second conductive surface 60 of the crystal 56 to provide acoustic dampening.
- the circuit board 50 A is then inserted into the first leg interior cavity 38 A with the back side 72 A up against the planar wall 34 A.
- the width of the circuit board 50 A is slightly less than the width of the interior cavity 38 A so that it can be placed therein but it properly positions the crystal spaced from the planar wall 34 A and semi-cylindrical wall 32 A.
- a silicone insulating tube 74 A is inserted in the cavity spaced between the semi-cylindrical wall 32 A and the crystal second conductive surface 60 to bias the circuit board 50 A against the planar wall 34 A.
- a similar procedure is then used to install the second crystal assembly 24 B in the second cavity 38 B.
- a two part epoxy 76 is used to pot the interior space 40 and interior cavities 38 A and 38 B.
- the cable 26 A is soldered to the terminal pads 54 A as at 78 and a shrink tube 80 placed over this connection to insulate the connection.
- the measurement circuit 20 is connected to two of the crystal assemblies 24 .
- One crystal assembly is used for the transmit function, the other crystal assembly is used for the receive circuit.
- the particular function depends on electrical connections made to the measurement circuit 20 , rather than position in the transducer housing 22 .
- the transducer 14 transmits and receives acoustic signals under control of the measurement circuit 20 to detect presence or absence of a material in the gap cap G.
- the particular form of the acoustic signal and the control implemented by the measurement circuit 20 do not form part of the invention. Instead, the invention is directed to the transducer, or sensor assembly, construction and the method of making the same.
- the printed circuit board is used to provide numerous advantages over prior sensor assemblies.
- the circuit board 50 provides electrical connection to the crystal 56 .
- the thickness of the circuit board 50 acts as a spacer between the crystal 56 and the walls 34 A or 34 B.
- the circuit board 50 assures proper location of the crystal 56 so that other electrical insulating materials are not required.
- the use of a printed circuit board enables use of automated assembly technology.
- the resultant crystal assembly 24 is more consistent and reliable.
- the circuit board 50 is designed to mate directly to the coaxial cable 26 .
- the printed circuit board 50 provides for additional functional test capability.
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
An ultrasonic point level measurement instrument comprises a measurement circuit and a transducer. The transducer transmits and receives acoustic signals under control of the measurement circuit. An improvement in the transducer comprises a transducer housing including a pair of spaced apart legs to define a gap therebetween. Each leg includes an interior cavity. A pair of crystal assemblies each comprise a crystal mounted to a circuit board. The circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg. A pair of cables are each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
Description
- There are no related applications.
- This invention relates to an ultrasonic point level measurement instrument and, more particularly, to an improved transducer and method of assembling a transducer.
- Knowledge of level in industrial process tanks or vessels has long been required for safe and cost-effective operation of plants. Many technologies exist for making level measurements. These include buoyancy, capacitance, ultrasonic and microwave radar, to name a few. Level measurement instruments may provide a continuous signal indicating level of the material in a tank or vessel, or may comprise point level measurement instruments that indicate the presence or absence of the material at a discrete level in the tank or vessel.
- Ultrasonic level measurement instruments are designed for non-contact sensing or contact sensing. Contact liquid level sensing for point measurement is achieved by using continuous-wave or pulse-signal technology. Continuous-wave instruments have two piezoelectric crystals mounted opposite each other in a transducer body, separated by a gap. The transmit crystal produces an acoustical signal when subjected to an implied voltage from an amplifier circuit. The receive crystal converts the acoustical signal that it receives into an electrical signal, which becomes the input of the same amplifier circuit. When liquid is present in the transducer gap, the amplifier becomes an oscillator causing a relay circuit in the electronics to indicate a wet gap condition. When liquid vacates the gap, the amplifier returns to an idle state.
- In pulse-signal units, a digital electronic amplifier produces a powerful pulse of ultrasonic energy more powerful than with most continuous-wave instruments. This allows measurement in conditions that include aeration, suspended solids, turbulence, and highly viscous liquids. Pulses of high-frequency ultrasonic energy milliseconds in duration are produced by the transmit crystal. In between each pulse, the receive crystal “listens” for the transmission. If liquid is present in the gap, the receive crystal detects the pulse and reports a wet gap condition to the electronics. When the gap is filled with air, the receive crystal cannot detect a pulse and reports a dry gap condition.
- A transducer in one known form, sometimes referred to as tip-sensitive style, includes a housing with a pair of spaced apart legs to define a gap therebetween. Piezoelectric crystal assemblies that form the sensor drive and receive elements are hand assembled. They must have a plurality of spacers glued to one of the crystal surfaces to provide proper positioning. Wires must be attached to each side of the crystal for electrical connection. Electrical insulating spacers are placed inside the transducer housing. After the two crystal assemblies are placed in the sensor tip, the sensor assembly is potted. Thereafter, coaxial cables must be attached to the crystal wires, as by splicing. Thereafter, the electrical connections must be potted. This manual process can be time consuming. Also, there can be lack of uniformity in construction of the crystal assemblies and thus the sensor assembly.
- The present invention is directed to improvements in ultrasonic sensor assembly.
- In accordance with the invention, there is provided an improved ultrasonic sensor assembly and method.
- There is disclosed in accordance with one aspect of the invention, an improvement in an ultrasonic point level measurement instrument comprising a measurement circuit and a transducer. The transducer transmits and receives acoustic signals under control of the measurement circuit. The improvement comprises a transducer housing including a pair of spaced apart legs to define a gap therebetween. Each leg includes an interior cavity. A pair of crystal assemblies each comprise a crystal mounted to a circuit board. The circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg. A pair of cables are each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
- It is a feature of the invention that each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board. Each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.
- It is another feature of the invention that each circuit board insulates one side of the crystal from the walls of the leg and an insulating spacer insulates another side of the crystal from the walls of the leg. The insulating spacer biases the circuit board against one of the walls of the leg.
- It is still another feature of the invention that the interior cavities are encapsulated with a compound, such as an epoxy.
- There is disclosed in accordance with another aspect of the invention a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit. The transducer transmits and receives acoustic signals under control of the measurement circuit. The transducer comprises a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body. The legs are generally semi-cylindrical with facing planar walls to define a gap therebetween. Each leg includes an interior cavity opening into the body. A pair of crystal assemblies each comprise a crystal mounted to a circuit board. The circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall. A pair of cables is each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
- There is disclosed in accordance with a further aspect of the invention the method of assembling a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer for transmitting and receiving acoustic signals under control of the measurement circuit, comprising: providing a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body; assembling a plurality of crystal assemblies, for each comprising mounting a crystal to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad; inserting a crystal assembly in the interior cavity of each of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and electrically connecting a cable between the measurement circuit and the terminal pad of each of the crystal assemblies so that the measurement circuit can detect presence of a material in the gap.
- Further features and advantages of the invention will be readily apparent from the specification and from the drawings.
-
FIG. 1 is a side elevation view of an ultrasonic point level measurement instrument including an ultrasonic sensor assembly in accordance with the invention; -
FIG. 2 is a side elevation view of the ultrasonic sensor assembly in accordance with the invention removed from the instrument ofFIG. 1 ; -
FIG. 3 is a top plan view of the ultrasonic sensor assembly ofFIG. 2 ; -
FIG. 4 is a sectional view taken along the line 4-4 ofFIG. 2 ; -
FIG. 5 is a sectional view taken along the line 5-5 ofFIG. 4 specifically illustrating a crystal circuit assembly with other parts removed for clarity; and -
FIG. 6 is a schematic/block diagram of the point level measurement instrument ofFIG. 1 . - Referring to
FIG. 1 , aprocess instrument 10 according to the invention is illustrated. Theprocess instrument 10 uses ultrasound technology for measuring point level. Particularly, an acoustic signal is transmitted between crystals to detect presence or absence of a material in a gap. - The
process instrument 10 includes acontrol housing 12, atransducer 14 and anextension rod 16 connecting thetransducer 14 to thecontrol housing 12. Theextension rod 16 may include a threadedfitting 18 for connection to a process vessel. Alternatively, a flange or other structure may be used. - The
control housing 12 houses ameasurement circuit 20, seeFIG. 6 . Themeasurement circuit 20 is electrically connected, as described more particularly below, to a sensor assembly in the form of thetransducer 14. In accordance with the invention, a less expensive and more consistent process is used for producing thetransducer 14. - Referring particularly to
FIGS. 2-4 , the transducer, i.e., sensor assembly, 14 includes ametal housing 22, a pair ofcrystal assemblies cables respective crystal assemblies measurement circuit 20, seeFIG. 6 . - The
housing 22 includes a generallycylindrical body 28 with a pair of spaced apartlegs body 28. Thelegs first leg 30A comprises asemi-cylindrical wall 32A connected to aplanar wall 34A. Similarly, thesecond leg 30B includes asemi-cylindrical wall 32B connected to aplanar wall 34B. A distal end of eachleg bottom wall interior cavity interior space 40 of thebody 28. As is apparent, the radius of thesemi-cylindrical walls body 28 to provide a continuous, seamless construction, as is particularly apparent inFIG. 4 . Upper ends of theplanar walls bridge wall 42. Theplanar walls - The
transducer housing 22 can be formed of various materials such as, for example, stainless steel. The particular material used for thehousing 22 does not itself form part of the invention. Moreover, while thehousing 22 is illustrated as being cylindrical with generally semi-cylindrical legs, other constructions can be used to form a gap. - Referring to
FIG. 5 , acrystal assembly 24 is illustrated. In accordance with the invention, thecrystal surface FIG. 5 and omitting the suffix A or B. - The
crystal assembly 24 includes a printedcircuit board 50. The printed circuit board includesconductive crystal pads 52 andterminal pads 54. As is conventional, the printedcircuit board 50 is made of an insulating material. Thecircuit board 50 has various conduction traces or paths on either side and some covered by insulating layers and the like.FIG. 5 does not specifically illustrate the conductive paths. However, as will be apparent to one skilled in the art, the conductive paths connect thecrystal pads 52 and theterminal pads 54 and other devices as illustrated schematically inFIG. 6 , discussed below. Where the paths are located and how they are traced on the printedcircuit board 50 is generally a matter of choice. - A
crystal 56 is generally planar and include opposite first and secondconductive surfaces FIG. 6 . The firstconductive surface 58 contacts thecrystal pads 52 so that the secondconductive surface 60 faces away from thecircuit board 50, as shown inFIG. 5 . A twopin connector 62 is electrically connected between the secondconductive surface 60 and theboard 50. Aresistor 64 is also mounted to thecircuit board 50. Surface flow soldering is used to provide connections between thedevices circuit board 50, with the connections from theconnector 62 to the crystal secondconductive surface 60 being made by soldering or the like. - Particularly, with reference also to
FIG. 6 , the electrical connections made by the various conduction paths are illustrated. Theterminal pad 54 is electrically connected to thecoaxial cable 26 by soldering acenter conductor 66 to one of theterminal pads 54, and using ajumper 68 to connect acoaxial cable shield 69 to theother terminal pad 54. Theshield 69 serves as a ground. - The
center conductor 66 is electrically connected from theterminal pad 54 to one pin of theconnector 62 to the crystal secondconductive surface 60. The other pin of theconnector 62 is connected to one side of theresistor 64. Theresistor 64 may be, for example, a 10K resistor which can be used for testing or other purposes. The other side of theresistor 64 is electrically connected to thecrystal pads 52 which are soldered to the crystal firstconductive surface 58. Thecrystal pads 52 are also electrically connected to thecable shield 68. - In the illustrated embodiment of the invention, the
crystal 56 is approximately ⅜″ square and 0.040″ thick. A conductive coating is placed on the opposite planar surfaces. The firstconductive surface 58 makes contact with theterminal pads 52. The secondconductive surface 60 makes contact with theconnector 62. Thecircuit board 50 includes a generally square shapedopening 70 disposed between the fourcrystal pads 52 and thus beneath thecrystal 56. - The process or method for assembling the
transducer 22 is now described. To assemble thetransducer 14, onehousing 22 and twocrystal assemblies cables conductive surface 60 of thecrystal 56 to provide acoustic dampening. Thecircuit board 50A is then inserted into the first leginterior cavity 38A with theback side 72A up against theplanar wall 34A. The width of thecircuit board 50A is slightly less than the width of theinterior cavity 38A so that it can be placed therein but it properly positions the crystal spaced from theplanar wall 34A andsemi-cylindrical wall 32A. Asilicone insulating tube 74A is inserted in the cavity spaced between thesemi-cylindrical wall 32A and the crystal secondconductive surface 60 to bias thecircuit board 50A against theplanar wall 34A. A similar procedure is then used to install thesecond crystal assembly 24B in thesecond cavity 38B. Next, a twopart epoxy 76 is used to pot theinterior space 40 andinterior cavities cable 26A is soldered to the terminal pads 54A as at 78 and ashrink tube 80 placed over this connection to insulate the connection. - Referring to
FIG. 6 , themeasurement circuit 20 is connected to two of thecrystal assemblies 24. One crystal assembly is used for the transmit function, the other crystal assembly is used for the receive circuit. The particular function depends on electrical connections made to themeasurement circuit 20, rather than position in thetransducer housing 22. As is conventional, thetransducer 14 transmits and receives acoustic signals under control of themeasurement circuit 20 to detect presence or absence of a material in the gap cap G. The particular form of the acoustic signal and the control implemented by themeasurement circuit 20 do not form part of the invention. Instead, the invention is directed to the transducer, or sensor assembly, construction and the method of making the same. - Thus, in accordance with the invention, the printed circuit board is used to provide numerous advantages over prior sensor assemblies. Particularly, the
circuit board 50 provides electrical connection to thecrystal 56. The thickness of thecircuit board 50 acts as a spacer between thecrystal 56 and thewalls circuit board 50 assures proper location of thecrystal 56 so that other electrical insulating materials are not required. Also, the use of a printed circuit board enables use of automated assembly technology. Theresultant crystal assembly 24 is more consistent and reliable. Also, thecircuit board 50 is designed to mate directly to thecoaxial cable 26. Finally, the printedcircuit board 50 provides for additional functional test capability. - Thus, in accordance with the invention, there is disclosed an improved sensor assembly and method of manufacturing the sensor assembly.
Claims (18)
1. In an ultrasonic point level measurement instrument comprising a measurement circuit and a transducer, the transducer transmitting and receiving acoustic signals under control of the measurement circuit, the improvement comprising:
a transducer housing including a pair of spaced apart legs to define a gap therebetween, each leg including an interior cavity;
a pair of crystal assemblies each comprising a crystal mounted to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad, each crystal assembly being received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg; and
a pair of cables each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
2. The improvement of claim 1 wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board.
3. The improvement of claim 2 wherein each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.
4. The improvement of claim 1 wherein each circuit board insulates one side of the crystal from the walls of the leg and an insulating spacer insulates another side of the crystal from the walls of the leg.
5. The improvement of claim 4 wherein each insulating spacer biases the circuit board against one of the walls of the leg.
6. The improvement of claim 1 wherein the interior cavities are encapsulated with a potting compound.
7. A transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer transmitting and receiving acoustic signals under control of the measurement circuit, the transducer comprising:
a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body;
a pair of crystal assemblies each comprising a crystal mounted to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad, each crystal assembly being received in the interior cavity of one of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and
a pair of cables each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.
8. The transducer of claim 7 wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board.
9. The transducer of claim 8 wherein each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.
10. The transducer of claim 7 wherein each circuit board insulates one side of the crystal from the planar wall and an insulating spacer insulates another side of the crystal from other walls of the leg.
11. The transducer of claim 10 wherein each insulating spacer biases the circuit board against the planar wall.
12. The transducer of claim 7 wherein the interior cavities are encapsulated with a potting compound.
13. The method of assembling a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer for transmitting and receiving acoustic signals under control of the measurement circuit, comprising:
providing a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body;
assembling a plurality of crystal assemblies, for each comprising mounting a crystal to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad;
inserting a crystal assembly in the interior cavity of each of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and
electrically connecting a cable between the measurement circuit and the terminal pad of each of the crystal assemblies so that the measurement circuit can detect presence of a material in the gap.
14. The method of claim 13 wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface is soldered to conductive pads on the circuit board.
15. The method of claim 14 wherein assembling a plurality of crystal assemblies further comprises electrically connecting connectors between the second conductive surfaces and conduction paths on the circuit boards.
16. The method of claim 13 wherein each circuit board insulates one side of the crystal from the planar wall and further comprising inserting an insulating spacer between another side of the crystal and other walls of the leg.
17. The method of claim 16 wherein each insulating spacer biases the circuit board against the planar wall.
18. The method of claim 13 further comprising encapsulating the interior cavities with a potting compound.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US11/213,221 US20070044708A1 (en) | 2005-08-26 | 2005-08-26 | Ultrasonic sensor assembly and method |
US12/290,082 US7874210B2 (en) | 2005-08-26 | 2008-10-27 | Ultrasonic sensor assembly and method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US11/213,221 US20070044708A1 (en) | 2005-08-26 | 2005-08-26 | Ultrasonic sensor assembly and method |
Related Child Applications (1)
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US12/290,082 Division US7874210B2 (en) | 2005-08-26 | 2008-10-27 | Ultrasonic sensor assembly and method |
Publications (1)
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US20070044708A1 true US20070044708A1 (en) | 2007-03-01 |
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US11/213,221 Abandoned US20070044708A1 (en) | 2005-08-26 | 2005-08-26 | Ultrasonic sensor assembly and method |
US12/290,082 Expired - Fee Related US7874210B2 (en) | 2005-08-26 | 2008-10-27 | Ultrasonic sensor assembly and method |
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US12/290,082 Expired - Fee Related US7874210B2 (en) | 2005-08-26 | 2008-10-27 | Ultrasonic sensor assembly and method |
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WO2010117536A3 (en) * | 2009-04-08 | 2010-12-09 | Illinois Tool Works Inc. | Ultrasonic sensor for detecting the presence or absence of liquid in a tube |
US7959732B1 (en) * | 2005-06-17 | 2011-06-14 | Saint-Gobain Ceramics & Plastics, Inc. | Apparatus and method for monitoring and controlling crystal growth |
CN103500870A (en) * | 2013-10-10 | 2014-01-08 | 中国科学院上海技术物理研究所 | Reflection type resonant cavity for measuring sample surface state in profound hypothermia high-intensity magnetic field |
CN103500869A (en) * | 2013-10-10 | 2014-01-08 | 中国科学院上海技术物理研究所 | Absorption type resonant cavity for measuring sample surface state in profound hypothermia high-intensity magnetic field |
US10072963B1 (en) * | 2014-07-11 | 2018-09-11 | Nick V. Solokhin | Ultrasonic volume-sensing transducer instrument with concave transceiver element |
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US9285261B2 (en) | 2012-09-12 | 2016-03-15 | Street Smart Sensors Llc | Acoustic flexural order level sensor |
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Also Published As
Publication number | Publication date |
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US20090056451A1 (en) | 2009-03-05 |
US7874210B2 (en) | 2011-01-25 |
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