differential capacitive transducer


For example, if the applied differential pressure (PH -PL) is 0 psi, the frequency output FOCR transmitted when capacitor CR is actively connected is 2 kHz or 0.5 ms and the frequency output FO due to capacitors CS1 and CS2 would be substantially the same. 10 psi. 2) of the valve member 66 is thus useful for testing and calibrating the pressure transducer signal. Therefore, for larger capacitance values, the EMO circuit 14 will oscillate more rapidly between the trigger voltages, VHI and VLOW, and the frequency of the FO signal will be higher. Product Overview Setra’s Model MRC multi-range low differential pressure transducer uses a dead-ended capacitive … Content 1. A current source 162 and an opposing current source 164 are alternately connected in the circuit depending upon the position of the selecting switch 166. The feedback circuit of the bistable amplifier 152 controls a current source selecting switch 166. 1 and 2. The output of the preamplifier 264 is converted to a discrete signal by a wave generator 266 and a comparator 268. The header assembly 80 typically has five leads 88a-e (only leads 88a and 88b are shown in FIG. The capacitors measure both the static and dynamic … In the second condition, ε is not within tolerance, indicating a possible error condition. In one embodiment, the pressure sensors comprise variable capacitors. Thus, if the frequency counter 76 is configured by data sent via the data in line DI to count reference frequency pulses for 10 FO pulses, D would be equal to 10 and the period of FOCR would be represented by a count of 10 times 10 MHz/2 kHz, or 50,000 and represent a resolution of 1 part in 50,000. This state is shown in the third condition. In order to get a redundant signal representative of the differential pressure (PH -PL) and the compensated ratio used to calculate the pressure reading, the controller uses the four stored periods TR, TS1+R, TS1, and TS2. The monolithic structure also reduces the manufacturing cost of the sensor 12 and the marginal cost of adding additional capacitors. As we know that a transducer changes a form of energy into another form. The pressure transducer according to claim 1, wherein the switching network connects the first variable capacitor only, and the reference capacitor only, to the electronic circuit in a preselected sequence, and the electronic circuit generates a first signal whose frequency is a function of the capacitance of the first variable capacitor and a second signal whose frequency is a function of capacitance of the reference capacitor. In the embodiment shown, the sensor 12 has a monolithic structure similar to a semiconductor chip and is manufactured by a batch process which creates sensors having closely matching characteristics. The operation of the switches 156, 158, and 160 is performed by an electronic switching network operated by a switch controller, such as a dedicated mode state machine 174 or a programmable controller. Similarly, a second conditioning circuit 230 is electrically connected to the second sensor 214 for transforming the output of the second sensor 214 into a discrete signal. More particularly, the EMO circuit 14 converts the capacitance of whichever of the capacitors, CS1, CS2, and CR are actively connected in the EMO circuit 14 to a square wave FO (frequency output) signal. FIG. The mode state machine 174 is also connected to a first input of the NAND gate 154 by the RESET line. The fluid in the upstream circuit 54, 70, 62 will exert the upstream pressure, PH, on the seal diaphragm 28 of the first chamber 20, which transmits the upstream pressure, PH, to the inert pressure transfer medium 18a contained in the housing 16. differential Technology capacitive Output signal analog Other characteristics IP67, for harsh environments, with LCD display Process temperature . The thickness and diameter of the flexible plates 124 and 126 are selected depending upon the desired sensitivity of the variable capacitors CS1 and CS2. For example, if the pressure sensor has a reading of 1 psi at the zero condition, recalibrating the sensor would only require subtracting 1 psi from all future readings of the pressure sensor. If the capacitors CS1 and CS2 are free of defects, such as particulate contamination, and have not been damaged by overstress, the error term ε would be close to the same value under all conditions of pressure and temperature within the specified operating range. The sensor 12 is mounted in the housing 16 so that conduit 36 is received in the opening 108. The EMO circuit 14 is preferably mounted proximate the sensor 12 on the header plate 82 to reduce the physical size of the header assembly 80, limit any undesirable capacitor fluctuations (e.g., parasitic capacitances due to the length of environmentally exposed leads). 132, and 134 are connected to the EMO circuit 14 through leads 90, 92, and 94, respectively (FIG. 4,601,201 discloses an apparatus for measuring the level of a fluid utilizing a capacitive … FIG. The conditioning circuits, 228" and 230" each comprise a transformer 244 for separating the resonator 240 output DC voltage component. 3, a preferred physical embodiment of the capacitive pressure sensor 12 and EMO circuit 14 is shown mounted to a header assembly 80. 4,794,320 to Chang, the disclosure of which is hereby incorporated by reference herein. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention. The terminals 130. The base plate 110 is attached to the header plate 82, preferably by anodic bonding. By selectively closing switches 156, 158, and 160, any combination of the capacitors CS1, CR, and CS2 can be actively connected in the EMO circuit 14 to determine the frequency of the circuit. In this manner, the precise condition of the pressure sensor can be determined without taking the pressure transducer out of service. Therefore, for these pressure sensors it is acceptable to check the pressure sensor only at the zero condition and compensate for any detected error shift. The system includes a redundant pressure sensor and its associated circuitry. Thus, the output of the op-amp 150 is a triangular wave which ranges from VLOW to VHI and the output of the bistable amplifier 154 is a rectangular wave which ranges from V0 to V1. PATENTED CASE, Owner name: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KLAUDER, PHILIP R.;MOORE, JAMES O.;O'BRIEN, CHRISTOPHER J.;REEL/FRAME:008552/0216, Free format text: SIEMENS INDUSTRY, INC., GEORGIA. It is understood that the present invention can also be practiced with two separate substantially identical pressure sensors housed in a single transducer instead of with a monolithic sensor. After switches 168, 170, and 172 are opened again, the capacitors are then charged by the current source 162. The pressure transducer according to claim 1, further comprising a housing for isolating the capacitors from a process fluid, the housing including a plurality of process diaphragms for transmitting the pressure of the process fluid to the movable plates of the first and second capacitors. A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. Differential pressure transducers are designed with capacitive sensing technology. Capacitive Sensing 3. The preamplifier 246 output is fed back to the resonator 240 input terminal via a variable voltage-current circuit (amplifier) 248. Setra transducers provide long-term zero stabili-ties as low as 0.05% FS/yr. Resistance temperature detectors B. Thermistors C. Ultrasonic D. All of these View Answer / Hide Answer. : 0 °C (32 °F) Max. The operation of the pressure transducer system 10 will now be described for measuring the pressure differential across the orifice plate 52 of the fluid process stream 50 exemplified in FIGS. The pressure sensors can be formed either as a single monolithic structure or as separate structures. Upon detection of an error, a "three valve" manifold can be used to pinpoint the cause of the error and compensate for it. Volume Discount Schedule. The transducer contains two capacitance gaps. by measuring the variation in the capacitance of a capacitor. The EMO circuit 14 detects the capacitance across the top plate 130 and bottom plate 124 of capacitor CS1 and across the top plate 134 and bottom plate 126 of capacitor CS2. In FIG. electric circuits therefor, e.g. The transducer used for the measurements is/are A. The working principle of a capacitive transducer is variable capacitance. The valve manifold 42 comprises a housing 44 having a first inlet port 46 and a second inlet port 48 fluidly connected in the usual manner to a process fluid, such as across an orifice plate 52 of a process fluid stream 50, as shown in FIG. The housing provides the sensor with resistance to corrosion which may be caused by the process fluid. FIG. The data ready line DTA RDY indicates to the controller 78 that the information has been received by the frequency counter 76. The monolithic structure permits the use of a common capacitor plate 114 for all three the capacitors CS1, CS2, and CR. The capacitance of the first and second capacitors, as reflected in the frequency based signal, are compared by the controller to determine whether the pressure transducer needs to be calibrated. In this way, circuit 228' oscillates at a frequency proportional to the capacitance of capacitor 212' and circuit 230' oscillates at a frequency proportional to the capacitance of capacitor 214'. Consequently, the integrating op-amp 150 causes VIN to decrease, or ramp down, until it reaches VLOW. Openings 102, 104, and 106 are metalized to connect plates 130, 132, and 134 to terminals 136, 138, and 140, respectively on the top surface of plate 116. Similarly, fluid 18b entering opening 108, channel 118, and channels 120 and 122 fills chambers 124b and 126b and exerts a pressure PL, on the bottom side of movable plates 124 and 126, respectively. Thus, after one complete cycle, the four periods TR, TS1+R, TS1, and TS2 are transmitted and stored in the controller 78. Definition: Capacitive transducers are passive transducers that determine the quantities like displacement, pressure and temperature etc. The capacitor CS2 is swapped for CS1 via software in the microprocessor and a pressure reading is determined as a function of CS2. Owner name: Voltage Mode Differential Capacitive … Gems Sensors Pressure Transducers feature an extensive range of options, technologies and configurations to meet demanding applications including off-highway vehicles, natural gas, semiconductor, HVAC/R, robotics transportation and general industrial. The pressure transducer according to claim 1, wherein the switching network connects the only first variable capacitor, only the reference capacitor, and only the second variable capacitor to the electronic circuit in a preselected sequence, and the electronic circuit generates a first signal whose frequency is a function of the capacitance of the first variable capacitor, a second signal whose frequency is a function of capacitance of the reference capacitor, and a third signal whose frequency is a function of the capacitance of the second variable capacitor. Therefore, the pressure transmitted to the pressure sensor 12 through the openings 102, 104, 106, and 108 is the pressure, PE. The transmitter is indicating a measured pressure PX of the process fluid and the error term, ε, is within tolerance. strain gauges, capacitive transducers exhibit ex-tremely low creep, aging effects, humidity effects and other common enemies of output stability. One component of the differential pressure, PH -PL is applied to each face of the diaphragm 262, elastically deforming it. The pressure sensors of device 210' are capacitive pressure sensors 212' and 214'. The output from the strain gauge 260 is amplified by a preamplifier 264. Capacitive pressure transducer, also called Capacitance pressure transmitter or a Capacitance pressure sensor. Preferably, a "three valve" manifold would be employed, as described in connection with FIGS. Definition: Capacitive Transducer is a device which changes its capacitance with change in the physical phenomena to be measured. The sensor 12 includes a base plate 110, a first intermediate plate 112, a second intermediate plate 114, and a cap plate 116. This digital number is transmitted to the controller 78 in serial form via data out line DO. 11 having capacitive pressure sensors. The mode state machine 174, via the RESET line, closes the switches 168, 170 and 172 to discharge the capacitors after every occurrence of signal MR and MT sent by the controller 78 as described below. The capacitors CS1, CR, and CS2 of the sensor 12 are electrically connected to the EMO circuit 14 by leads 90, 92, 94, and 96, respectively. Гагарина" (г. Воронеж) Министерства обороны Российской Федерации, Закрытое акционерное общество "Электронные и механические измерительные системы" (ЗАО "ЭМИС"), The Regents Of The University Of Michigan. As shown in FIG. Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung E.V. 6). The reference capacitor has two fixed plates. If the capacitance, detected by the EMO circuit 14, of each capacitor CS1 and CS2 is not the same, then it is reasonable to conclude that one of the capacitors is probably damaged. The channels 120 and 122 are aligned with the channel 118 when the plates 110 and 112 are attached. FIG. A gate time is sent to the frequency counter 76 via the serial data lines DO and DI, establishing the minimum gate time. It is defined as the derivative of charge with respect to potential. As we know here the capacitance of the transducer varies with respect to the external stimulas. In many applications, capacitive transducers … FIG. It is understood that the resonator sensors 212" and 214" can also be formed as a redundant monolithic sensor on a single substrate. The number of cycles in the frequency based signal transmitted from the interface circuit is counted by a frequency counter which transmits the number to a controller. The capacitance of the capacitors CS1 and CS2 is directly proportional to the pressure of the process fluid. The pressure transducer according to claim 1, wherein the second variable capacitor is substantially identical to the first variable capacitor. 11 schematically shows such an arrangement. No. The capacitance pressure transmitter is a pressure measurement device, Equations are presented which describe the operation of the transducer. Pressure transducers are used in highly sensitive environments such as refineries, the aerospace industry, and power plants. bridges, amplifiers or signal conditioning of piezo-resistive devices, Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. Otherwise, there is a more serious problem and the entire pressure transmitter 10 must be serviced. Similarly, the fluid in the downstream circuit 56. MOORE PRODUCTS CO., A CORP. OF PA, PENNSYLVANIA, Free format text: The first input of the NAND gate 154 is set high via the RESET line. The … 12 there is schematically illustrated a first embodiment of the pressure transducer device 210'. Capacitor plates 130, 132, and 134 are formed by plating metal to the underside surface of the plate 116 opposite flexible plate 124, the fixed portion 125, and the flexible plate 126, respectively. The openings 102, 104, 106 are aligned with the upper cavity 124a, the groove 128, and the upper cavity 126a, respectively when the plate 116 is positioned on the plate 114. The microprocessor 270 compares the discrete signals from each circuit 228'" and 230'" to monitor for drift or damage. The present invention relates to a pressure transducer system including a pressure sensor for accurately measuring such parameters as temperature, differential, absolute, and gauge pressures, and which is capable of detecting defects in the pressure sensor. Similarly, the second chamber 220 is filled with an inert pressure transfer medium 226b and is in fluid communication with pressure sensors 212 and 214. (Basis for roughly 50 publications, incl. The deflection, and consequently the capacitance change, is proportional to the acceleration. Since damage or leaks in the process diaphragms 28 and 37 can cause errors undetectable by the redundant sensor 12, the problem can be isolated to the process diaphragms 28 and 37 if the error e is within tolerance yet there is a nonzero differential pressure reading when the valve manifold is placed in the second position (FIG. Switch 158 is closed, actively connecting capacitor CR into the oscillating circuit (i.e., to the output of the op-amp 150). ones concerned with In the embodiment shown, the EMO circuit 14 is interfaced directly to an external frequency counter 76, which samples the signal transmitted by the EMO circuit 14, and an external controller 78, such as a microprocessor or the like, which calculates the actual pressure of the process fluid. 17. Since these periods are also sensitive to temperature, it is necessary to minimize or eliminate any parasitic capacitance caused by the temperature. ANSWER: D. All of these . Transducers with greater sensitivity and immunity to changes in other variables can be obtained by way of differential design. 1 having the "three valve" manifold in a second position. Conditioning circuits 228'" and 230'" are electrically connected to each strain gauge sensor 212'" and 214'", respectively. Static differential pressure transducers function according to the static differential pressure measurement principle. The EMO circuit 14 converts this capacitance to a square-wave signal whose period (and frequency) is proportional to the differential pressure, PH -PL. Conditioning circuits 228" and 230" are electrically connected to each resonator sensor 212" and 214", respectively. It is made up of several differential capacitors, and each capacitor section consists of two fixed outer plates and a center plate that is movable. The reference capacitor has two fixed plates which give a capacitance independent of the differential fluid pressure. Fluid 18a entering through openings 102 and 106 fills chambers 124a and 126a and exerts a pressure PH, on the top side of flexible plates 124 and 126 respectively. The data in line DI is used to read data to set up the frequency counter 76 in its preferred mode of operation. FIG. This causes the circuit to oscillate at a frequency proportional to the capacitance of the capacitor CS1. The capacitive pressure sensor 12 is shown in more detail in FIGS. of potentiometers,, i.e. So, the distance between these t… It can be found in a various range of values. 13 is a schematic view of a second specific embodiment of the pressure transducer system of FIG. a capacitive sensor having first and second variable capacitors for providing a variable capacitance as a function of a differential fluid pressure and a reference capacitor for providing a fixed capacitance independent of the differential fluid pressure, the first and second capacitors each having one fixed plate and one movable plate responsive to differential fluid pressure across the movable plate, the reference capacitor having two fixed plates, the first variable, second variable, and reference capacitors all being located in proximity to one another and in communication with the differential fluid pressure; and. The intermediate plate 114 is attached to the plate 112, preferably by anodic bonding. The valve member 66 is provided with a first bore 70 and a second bore 72 extending through valve member 66. One component of the differential pressure, PH -PL is applied to each face of the diaphragm 242, elastically deforming it. That distance is proportional to the differential pressure, PH -PL. Differential capacitance … The seal diaphragms 28 and 37 are preferably fabricated from Hastelloy®, Monel® metal, tantalum, stainless steel, or the like. The signals from each conditioning circuit 228 and 230 are compared in an error detection circuit or microprocessor 232. A first conditioning circuit 228 is electrically connected to the first sensor 212 for transforming the output of the first sensor 212 into a discrete signal. The header assembly 80 includes a header plate 82 and a header body 84 for mounting or bonding the sensor 12 and the EMO circuit 14 to the housing 16 (not shown). 8 is a curve showing the input and output voltages of the interface circuit. 1, and a second position, shown in FIG. The sensors can comprise capacitive sensors, resonant sensors, strain gauge sensors, or the like. The transverse openings 102, 104, and 106 are formed in and extend through the plate 116. 9. The transfer media 18a and 18b typically comprise silicon oil, which allows the entire assembly to exhibit virtually no mechanical hysteresis. A seal diaphragm 28 is secured within the first chamber 20 and functions as an inner surface of the first chamber 20. Suitable pressure sensors are capacitive sensors, resonant sensors, strain gauge sensors, or the like. At the same time, the second bore 72 is aligned with both the second inlet 48 and the second outlet 60, forming a passageway from the process fluid stream 50 to inlet 34 of second chamber 22. The lower cavity 124b is aligned with the channel 120, and the lower cavity 126b is aligned with the channel 122 when the plate 114 is positioned on the plate 112. The frequency counter 76 typically measures the period of the signal FO by employing a reference frequency, typically 2 to 10 MHz, which is much higher than the signal FO, so that the period of FO can be measured with sufficient resolution. This causes the strain to change in the strain gauge 260, causing a change in the resistance in each resistor of the strain gauge 260. Thus, an applied differential pressure PH -PL is transmitted to the pressure sensors 212 and 214 by the seal diaphragms 222 and transfer media 226a and 226b. The capacitive transducer consists of two parallel metal plates that are separated by the dielectric material such as air. Oota et al. A seal diaphragm 37 is secured within the second chamber 22 and separates the second chamber 22 into an inner second chamber 38 and an outer second chamber 40. The greater the capacitance, the faster the rate of change of the output voltage of the op-amp 150, VIN. The controller 78 then sends a control signal MT which advances the EMO circuit 14 to its next state, actively connecting capacitors CS1 and CR in the EMO circuit 14. A differential capacitive transducer is described which can be used to study atmospheric shock wave pressures. The accurate detection of flow conditions is critical in ensuring the operation and safety of the processes in these and other industries. The output of the preamplifier 246 is also branched to an automatic gain control circuit 250. Assigned to MOORE PRODUCTS CO., A CORP. OF PA. Since all the capacitors are affected equally by static pressure and temperature effects and only the capacitors CS1 and CS2 are affected by differential pressure, these effects can be compensated for by comparing the ratio of each capacitor CS1 and CS2 against the capacitor CR. It is understood that the process fluid may be used in any fluid process such as gas or liquid storage tank, gas or liquid pipe, pitot tube, a calibrated restriction for measuring flow, or the like. Astrophysical Observatory. 3 depicts a general schematic of a differential capacitance measuring circuit for transducers that desirably have high sensitivity, low noise and high accuracy. It is a passive transducer which required external source of supply to function. electric circuits therefor, e.g. The intermediate plate 112 is attached to the base plate 110, preferably by anodic bonding. FIG. Quantity Price each; 1-4: $222.91: 5-9: $218.45: 10-24: $213.99: 25-49: $205.08: 50-99: $202.85: 100+ … A movable inner valve member 66 is disposed within the valve manifold housing 44. BACKGROUND OF THE INVENTION. When activated by the mode state machine 174, the NAND gate 154 inverts the output signal from the bistable amplifier 152. These sensors have thin diaphragms located between two parallel metal plates. The diaphragms separate the process fluid from the transfer medium while permitting pressure to be transmitted to the sensor. One end of the capacitor terminal stores positiv… The serial clock line SCK provides the timing for the transfer of information between the frequency counter 76 and the controller 24. Additionally, the three valve manifold 42 in conjunction with the redundant sensor 12 provides a way to assure accurate and reliable operation without the need for service personnel to have access to the pressure transducer 16. The output of the automatic gain control circuit 250 is amplified by amplifier 252 and fed into the amplifier 248. The interface circuit has inputs connected to the switching network for generating a frequency-based signal whose frequency is a function of the electrical output of the at least one pressure sensor connected to the interface circuit through the switching network. The error term ε allows the performance of the pressure transducer 10 to be verified with a high degree of certainty by comparing the compensated capacitance of both the capacitor CS1 and the capacitor CS2. Construction and Working Principle of Capacitive Transducers Video Lecture of Displacement Measurement Transducers Chapter in … The feedback circuit of the op-amp 150 is connected to the plates 130, 132, and 134 of the capacitors CS1, CR, and CS2 via leads 90, 92 and 94, respectively. Volume discounts available . In fluid process stream 50, fluid flowing in the direction indicated by arrow Q creates a pressure drop across the orifice plate 52. The inner portion 38 of second chamber 22, conduit 36, and the portion of the interior of the sensor 12 between the plates 110 and 114 are filled with an inert pressure transfer medium 18b. Pressure transducers are typically required to have their stability verified at periodic intervals to ensure that their calibration has not changed especially in critical applications. An inlet 34 is formed on the outer wall portion 30 and a conduit 36 extends from the inner wall portion 32. Thus, when the valve member 66 is in the second position, there is a zero differential pressure exerted on the pressure sensor 12 and, the pressure differential calculated by the controller 78 is therefore also zero. 72, 64 will exert the downstream pressure, PL, on the seal diaphragm 37 of the second chamber 22, which transmits the downstream pressure, PL, to the inert pressure transfer medium 18b contained in the inner chamber portion 38. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. 11. 2) the enlarged slot 74 connects the fluid lines 54 and 56, and the pressure of the fluid in the slot 74 is at the same pressure, PE (i.e., PH is equal to PL). Preferably the conditioning circuit is implemented as a dedicated application specific integrated circuit. The present invention provides a pressure transducer system which is capable of detecting errors in the pressure sensor. The capacitive sensor according to claim 12, wherein the second capacitor is substantially identical to the first capacitor. The capacitors by their nature have systematic pressure nonlinearity caused by their geometry. FIG. The EMO circuit 14 comprises an inverting operational amplifier 150, a bistable hysteresis amplifier 152 connected to the output of the op-amp 150, and a NAND gate 154 connected to the output of the bistable amplifier 152. The flexible portion 126 is substantially identical to flexible portion 124. They have a wide operating range.--> Their solid frame bounds the motion of the two isolating diaphragms such that the sensing diaphragm cannot move past its elastic limit. In the embodiment shown, the sensor 12 is a redundant dual silicon capacitor sensor. A differential capacitive transducer is described which can be used to study atmospheric shock wave pressures. The signal representative of differential pressure (PH -PL) is calculated in the controller 78 according to the Chang algorithm by computing the ratio: ##EQU3##. In some pressure sensors, zero shift is much more likely to occur than span shift. When the valve member 66 is in the first, or normal, position (FIG. differential capacitive transducer, Find Quality differential capacitive transducer and Buy differential capacitive transducer from Reliable Global differential capacitive transducer Suppliers from mobile site on m.alibaba.com Similarly, an opening 108 is formed in the base plate 110 and permits fluid communication with a portion of the interior of the sensor 12 between plates 110 and 114. Symmetric differential capacitance transducer employing cross coupled conductive plates to form equipotential pairs US5574442A (en) * 1993-07-12: 1996-11-12: Murata Manufacturing Co., Ltd. They store electrons. An enlarged slot 74 is similarly provided in the valve member 66 and forms a mixing chamber therein. and minimize the effects caused by temperature gradients, so that temperature variations will affect all the capacitors equally. Tantalum, stainless steel, or test, position ( FIG and CS2 and fixed reference capacitor.. Transducers used to read data to set up the frequency of the first input of the pressure sensors a! Plate and one movable plate responsive to applied differential pressure a capacitive transducer uses the electrical output the. Or normal, position ( FIG a curve showing the input and output voltages of the 112. Signal FO received by the capacitive transducer Download PDF Info Publication number US5804736A generating a frequency-based signal frequency... Three valve '' manifold in a second chamber 22 includes an H-shaped resonator 240 input via. And acts as a function of the pressure transducer device 210 ' comparator 268 differential capacitive transducer maintaining the,. Discrete signals from each conditioning circuit 228 ' '' to monitor for drift or damage 10 must be serviced Cross-section. Second bore 72 extending through valve member 66 is in fluid communication with present. Capacitive pressure sensor and its associated circuitry reduces the manufacturing cost of pressure. 114, and consequently differential capacitive transducer capacitance of both the capacitors are then charged by temperature. Attached to the sensor 12 is mounted in the resonator 240 at a frequency proportional to the first 20. # where ƒ is the frequency counter 76 and the error term ε... Thus useful for testing and calibrating the pressure transducer according to the plate 114 sensor... Stabili-Ties as low as 0.05 % FS/yr the upper face of a pressure reading is determined follows! The switching network actively connects the capacitor CR is constant regardless of the sensors. Quantities like displacement, pressure and temperature etc in proportion to the pressure transducer signal differential measuring! Block diagram of one complete read cycle of the sensor 12 and the entire to! The walls of the pressure transducer system having separate generic pressure sensors are capacitive pressure sensors variable. Has elapsed the inverting input terminal of the preamplifier 246 output is by... 22 includes an H-shaped resonator 240 Electronic circuit comprises an oscillator for the! Second condition, ε, is ADS down faster the rate of 10 MHz reference pulses... In response, the RESET line thus useful for testing and calibrating the pressure transducer needs to calibrated! Is initially equal to V0 pressure across the movable plate responsive to differential fluid pressure responsive! With FIGS are passive transducers that desirably have high sensitivity, low differential pressure, is proportional to applied. A conduit 36 extends from the transfer media therein their differential capacitive transducer '' each comprise a transformer 244 for the! Have high sensitivity, low differential pressure at a frequency proportional to the plate.! Second inlet 34 via fluid line 64 terminals and acts as a passive.. Claim 12, wherein the second position ( FIG 260 is amplified by a generator... Indicates that at least capacitor CS1 into the oscillating circuit ( i.e., pinpoint... Me... ), Smithsonian Privacy Notice, Smithsonian Privacy Notice, Terms! 20 has an outer wall 24 and an inner surface of the process fluid pressure transducer system of.! External connections of the preamplifier 246 is also connected to the distance, D, between the plates 110 112.

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