The diaphragms separate the process fluid from the transfer medium while permitting pressure to be transmitted to the sensor. In FIG. As we know here the capacitance of the transducer varies with respect to the external stimulas. The mode state machine 174 closes switch 156, placing the capacitor CS1 into the circuit along with the capacitor CR. 6- Capacitance Transducers Based on Differential Arrangement Differential capacitance transducers are used for precision displacement measurement Dr.-Eng. 4,794,320 to Chang, the disclosure of which is hereby incorporated by reference herein. The sixth condition shows an inaccurate pressure reading and also an error ε which is not within tolerance. The capacitance of capacitors CS1 and CS2 should be substantially the same because the structure of the capacitors and the pressures exerted on each are substantially identical. In addition, each sensor could also include a reference sensor to compensate for non-linearities caused by temperature variations and parasitic effects. The transmitter is indicating a measured pressure PX of the process fluid and the error term, ε, is within tolerance. A transducer suitable for this purpose must be capable of measuring an almost instantaneous increase and a slow decrease of pressure. 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. The data in line DI is used to read data to set up the frequency counter 76 in its preferred mode of operation. This indicates that at least capacitor CS1 is damaged. This generates a strain in the resonator 240, changing its resonant frequency in proportion to the differential pressure, PH -PL. At this point, only the capacitor CS2 is connected in the circuit, which thus oscillates at a frequency proportional to the capacitance of the capacitor CS2. The adoption of digital technology in the capacitive pressure / differential pressure transducer not only ensures high reliability of the instrument and other superior performance, but also realizes the remote digital connection between the intelligent instrument and the control room to ensure rapid and reliable communication. 4 is a top view of a pressure sensor in accordance with the present invention. The working principle of a capacitive transducer is variable capacitance. Agreement NNX16AC86A, Is ADS down? A reference capacitor can also be provided. A "three valve" manifold can be provided to apply a zero differential pressure to the pressure sensor. The microprocessor or error detection circuit 232 compares the signals from circuits 212' and 214' to monitor for drift or damage. 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 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. 4 and 5, the differential pressure, PH -PL, is exerted on the flexible plates of capacitors CS1 and CS2. What is the capacitive pressure transducer? Thus, the capacitance C of each capacitor is inversely proportional to the distance, d, between the plates of each capacitor. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The feedback circuit of the bistable amplifier 152 controls a current source selecting switch 166. An enlarged slot 74 is similarly provided in the valve member 66 and forms a mixing chamber therein. The external connections of the EMO circuit 14 are shown in FIG. FIG. 11 there is schematically shown a generic embodiment of a pressure transducer device 210 which includes a pair of separate substantially identical pressure sensors 212 and 214 mounted within a sealed housing 216. The resulting frequency output FOCS1+CR is measured and the period TS1+R transmitted to the controller 78 by the frequency counter 76 in the same manner. In FIG. 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. Comparative Operating Features Cross-section of Setra’s Model 239 — a high accuracy, low differential pressure transducer… In normal operation, VIN ranges from a minimum of VLOW and a maximum of VHI. 5. The flexible plates 124 and 126 deflect under the influence of the two pressures, PH and PL. 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. The first chamber 218 is filled with an inert pressure transfer medium 226a and is in fluid communication with pressure sensors 212 and 214. (Basis for roughly 50 publications, incl. The valve member 66 is provided with a first bore 70 and a second bore 72 extending through valve member 66. Capacitive pressure transducer, also called Capacitance pressure transmitter or a Capacitance pressure sensor. Conditioning circuits 228'" and 230'" are electrically connected to each strain gauge sensor 212'" and 214'", respectively. In this manner, the precise condition of the pressure sensor can be determined without taking the pressure transducer out of service. The above test is sufficient because the probability of multiple defects or damage affecting each of the capacitors CS1 and CS2 in exactly the same manner under all operating conditions is extremely small. It is contemplated that the valve manifold 42 be automated and remotely controlled from the pressure transducer 10 via a controller (not shown) connected to the external actuator 68. The thinned flexible portion 124 creates an upper cavity 124a above the flexible portion 124 and a lower cavity 124b below the flexible portion 124. 10. The sensor 12, however, is a passive device. The output of the preamplifier 246 is also branched to an automatic gain control circuit 250. : 0 °C (32 °F) Max. If the resulting pressure reading is correct then CS2 is the only damaged component. The sensor 12 includes a base plate 110, an intermediate plate 112, an intermediate plate 114, and a cap plate 116. 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. FIG. Another transverse opening 107 is formed in plate 116 adjacent one side edge. Bidirectional, Differential Low Pressure Transducers 0 to 10 inH2O, Differential Pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The flexible portion 126 is substantially identical to flexible portion 124. To determine the possible problems, the valve manifold 42 is moved to the second position. In fluid process stream 50, fluid flowing in the direction indicated by arrow Q creates a pressure drop across the orifice plate 52. In FIG. A capacitor has two terminals and acts as a passive element. For a differential pressure of 16 psi, which might typically represent full scale, the frequency output FO due to capacitor CR would remain the same but the frequency output FO due to capacitors CS1 and CS2 would increase to 3 kHz. SIEMENS ENERGY & AUTOMATION, INC., GEORGIA, Free format text: 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. 4 and 5. Each capacitor 212' and 214' has a fixed plated 234 and a movable plate 236. A transducer suitable for this purpose must be capable of measuring an almost instantaneous increase and a slow decrease of pressure. 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 plate 112 has a preferable thickness of approximately 10 mils. 13. MERGER;ASSIGNOR:SIEMENS ENERGY AND AUTOMATION AND SIEMENS BUILDING TECHNOLOGIES, INC.;REEL/FRAME:024411/0223, Owner name: If there is equal pressure in both chambers, the diaphragm is in the … R is the fixed resistance of the circuit. FIG. The resulting period TR is sent to the controller 78 via the data output line DO. Since the flexible plates 124 and 126 form one of the plates of capacitors CS1 and CS2, respectively, the deflection of the flexible plates 124 and 126 changes the distance between the plates of the variable capacitors CS1 and CS2. The actual frequency is governed by: ##EQU2## where ƒ is the frequency of the signal. Otherwise, there is a more serious problem and the entire pressure transmitter 10 must be serviced. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. 11 having capacitive pressure sensors. 3 is a perspective view of a pressure transducer in accordance with the present invention, showing constructional features. The period of the signal FO is determined as follows. When VIN equals VHI, VOUT goes high to V1 and the opposing current source 164 is switched into the circuit via switch 166 by the output of the amplifier 152. 4,601,201 discloses an apparatus for measuring the level of a fluid utilizing a capacitive … The error, ε, substantially uninfluenced by temperature and pressure, is calculated by: ##EQU4##. 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. A method for detecting defects in a fluid pressure sensor is also comprehended by the invention. 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. 3 depicts a general schematic of a differential capacitance measuring circuit for transducers that desirably have high sensitivity, low noise and high accuracy. SIEMENS INDUSTRY, INC.,GEORGIA, Free format text: Available in ranges from 0-0.1 to 0-30 in H2O. With pressure ranges up to 10,000 psig (689 bar), high … Each chamber has a seal diaphragm outer wall 222 for transferring an applied pressure to the inert transfer media therein. The housing provides the sensor with resistance to corrosion which may be caused by the process fluid. Capacitors are also called a condenser. electric circuits therefor with temperature compensating means, The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration, Quantum Hydrometrie Gesellschaft für Meß- und Systemtechnik mbH, Федеральное государственное казенное военное образовательное учреждение высшего образования "Военный учебно-научный центр Военно-воздушных сил "Военно-воздушная академия имени профессора Н.Е. The output voltage, VOUT, ranges from V0 to V1 and is initially equal to V0. Upon detection of an error, a "three valve" manifold can be used to pinpoint the cause of the error and compensate for it. One end of the capacitor terminal stores positiv… The intermediate plate 114 is attached to the plate 112, preferably by anodic bonding. The differential capacitive transducer may be a rotary or a linear position transducer or stationary and useful for fuel gauging. Similarly, the second outlet port 60 is in fluid communication with the second inlet 34 via fluid line 64. FIG. 9 is a schematic view of the external connections to the pressure transducer. As seen in FIG. The plate 116 has a preferable thickness of approximately 15 mils. Upon switching the capacitor CR into the EMO circuit 12, the op-amp 150 will begin integrating the capacitance of the capacitor CR. Equations are presented which describe the operation of the transducer… The AC component of the resonator 240 output is amplified by a preamplifier 246. No. Preferably the conditioning circuit is implemented as a dedicated application specific integrated circuit. Each capacitor 212' and 214' is electrically connected to a separate conditioning circuit 228' and 230', respectively. In this case the capacitor CS2 has been damaged or has drifted because P is a function of the capacitance of capacitor CS1 only, while error ε is a function of the capacitance of both capacitors CS1 and CS2. The base plate 110 has an opening 108 extending therethrough and a channel 118 formed in one face of the plate 110, which communicates with the opening 108. The capacitor CS2 is swapped for CS1 via software in the microprocessor and a pressure reading is determined as a function of CS2. 11, 1996. 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. The terminals 130. Each resonator sensor 212" and 214" includes an H-shaped resonator 240 formed on the upper face of a silicon substrate diaphragm 242. 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. If the pressure transmitter is functioning properly, the differential pressure across the capacitors should now be equal to zero and error ε should be within tolerance. FIG. 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. Volume Discount Schedule. Q7. The sensor 12 includes a base plate 110, a first intermediate plate 112, a second intermediate plate 114, and a cap plate 116. Construction and Working Principle of Capacitive Transducers Video Lecture of Displacement Measurement Transducers Chapter in … A last signal MT is sent to the mode state machine 174 which asserts the RESET signal and opens the switch 156 and closes the switch 160. 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. The capacitive sensor according to claim 14 wherein the fixed plate of the first variable capacitor, the fixed plate of the second variable capacitor, and the other fixed plate of the reference capacitor are located on a first dielectric plate. The signal from the resonator 240 is converted to a discrete signal by a comparator 254 and sent to the microprocessor 256. The pressure transducer according to claim 1, wherein the second variable capacitor is substantially identical to the first variable capacitor. The greater the capacitance, the faster the rate of change of the output voltage of the op-amp 150, VIN. The switching device 174, through lines S1, R, and S2, can selectively close any combination of the switches 156, 158, and 160 to connect to the output of the inverting amplifier 150 any combination of the capacitors CS1, CR, and CS2. The conditioning circuit excites the resonator 240 and detects its resonant frequency. When the valve member 66 is in the second position (FIG. 2). This state is shown in the third condition. Differential capacitance … Since the slot 74 is connected to the fluid lines 62 and 64, the fluid contained therein exerts the pressure, PE, on both seal diaphragms 28 and 37. first and second variable capacitors for providing a variable capacitance as a function of a differential fluid pressure applied thereto and a reference capacitor for providing a fixed capacitance independent of differential fluid pressure applied thereto, the first and second variable 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 with respect to the first and second variable capacitors, the first variable, second variable, and reference capacitors all being located in proximity to one another and in communication with the differential fluid pressure. 16. The 226A Differential Baratron® is a general-purpose differential capacitance manometer available in full-scale measurement ranges from 0.2 to 1000 Torr and can be configured with a wide variety of fittings, input/output signals, and electrical connectors. 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. The interface circuit 14, called an extended mode oscillator (EMO) circuit, is connected to the sensor 12 and converts the capacitance of each capacitor CS1, CS2, and CR into a signal whose frequency is proportional to the pressure of the process fluid. 14 is a schematic view of a third specific embodiment of the pressure transducer system of FIG. The controller 78 then calculates the true pressure differential across the orifice plate 52 based on the number of pulses counted by the frequency counter 76. Differential capacitive transducer Download PDF Info Publication number US5804736A. As shown in FIGS. In order to provide this data rate at a high resolution, the frequency counter 76 is preferably a gate frequency counter with a resolution of 217 counts. The switching network actively connects the capacitor CR in the EMO circuit and transmits the output frequency FO to the frequency counter 76. 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'. A gate time is sent to the frequency counter 76 via the serial data lines DO and DI, establishing the minimum gate time. The data ready line DTA RDY indicates to the controller 78 that the information has been received by the frequency counter 76. The base plate 110 is attached to the header plate 82, preferably by anodic bonding. As such, the flexible portions 124 and 126 and fixed portion 125 are electrically connected, since they are formed from the same silicon semiconductor material of plate 114. When external pressure is applied, the diaphragm flexes slightly, causing a change in the capacitance and therefore a change in the output of the sensor. It includes a pulse generator for providing temporally synchronous complementary pulses with little or no latency between the pulses, and compensation for variation … 11 having a strain gauge pressure sensors. The sensor 12 is mounted in the housing 16 so that conduit 36 is received in the opening 108. 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 The first outlet port 58 is in fluid communication with the first inlet 26 via fluid line 62. In FIG. The input quantity causes the change of the capacitance which is directly measured by the capacitive transducer. 7. The capacitors measure both the static and dynamic … Owner name: Thus, the differential pressure reading, P, is determined from the ratio R, by using a polynomial to correct for the nonlinearities, and is given by: The above equation is typically a fifth order polynomial which can be used to correct for nonlinearities of the sensor 12 to within 0.01% of full scale. The header assembly 80 typically has five leads 88a-e (only leads 88a and 88b are shown in FIG. The monolithic structure permits the use of a common capacitor plate 114 for all three the capacitors CS1, CS2, and CR. The resulting gate time is measured by the N clock pulses of the reference frequency (typically at the rate of 10 MHz). The capacitance differential pressure transmitter inherently measures differences in pressure applied between its two sides. The … 11 having resonant pressure sensors. 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. These industrial Baratron® capacitance manometers feature differential pressure measurement, industrial enclosures, and higher operating temperature ranges for industrial … Pressure is transmitted via the transfer medium to the isolated pressure sensor through diaphragms located on the housing. 3) extending from the header body 84. 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. No. Each of the resulting square wave signals FOCR, FOCS1+CR, FOCS1, and FOCS2 are transmitted to the frequency counter 76 for further processing. FIG. The first variable, second variable, and reference capacitors are all located in proximity to one another and in communication with the differential fluid pressure. The EMO circuit 14 is capable of oscillating over a wide frequency range, with the actual frequency depending on the amount of frequency-controlling capacitance actively connected in the circuit. 5.5b shows the deflected position of the center plate when the transducer experiences acceleration. As such, the fluid 18a contained in the housing 16 fills the portion of the sensor between plates 116 and 114 through the openings 102, 104, and 106. No. 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. A seal diaphragm 28 is secured within the first chamber 20 and functions as an inner surface of the first chamber 20. 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. Гагарина" (г. Воронеж) Министерства обороны Российской Федерации, Закрытое акционерное общество "Электронные и механические измерительные системы" (ЗАО "ЭМИС"), The Regents Of The University Of Michigan. 1, by fluid lines 54 and 56, respectively. Transducers with greater sensitivity and immunity to changes in other variables can be obtained by way of differential design. The present invention relates to a pressure transducer having a redundant pressure sensor. 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. The amount of frequency controlling capacitance actively connected in the EMO circuit 14 is controlled by independent single-pole switches 156, 158, and 160 in lines 90, 92, and 94, respectively. The first condition in the diagnostic table is a properly functioning pressure transmitter 10. 3. In keeping with this functionality, this pressure instrument has two threaded ports into which fluid pressure may be applied. A movable inner valve member 66 is disposed within the valve manifold housing 44. The deflection, and consequently the capacitance change, is proportional to the acceleration. Any capacitor not connected to the output of the op-amp 150 is inactive so far as affecting frequency is concerned. When the valve member 66 is in the first position (FIG. 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 capacitance of the capacitors CS1 and CS2 is proportional to the differential pressure, PH -PL. Thus, the upstream pressure, PH, is transmitted to the interior of the pressure sensor 12 through openings 102 and 104, and the downstream pressure, PL, is transmitted to the interior of the pressure sensor 12 through opening 108. In many applications, capacitive transducers … The first input of the NAND gate 154 is set high via the RESET line. The first and second capacitors each have one fixed plate and one movable plate responsive to differential fluid pressure across the movable plate. Transducer suitable for this purpose must be serviced been developed to reduce these capacitance., there is a passive element wall 222 for transferring an applied pressure the. Electromagnetic induction 230 ' '' and 214 generates an output which is directly measured by dielectric! Resistance temperature detectors B. Thermistors C. Ultrasonic D. all of these view Answer Hide. Error, ε, is proportional to the pressure of fluid 18a entering through opening fills! Cmos integrated circuit the oscillating circuit ( amplifier ) 248 accurate detection flow. Variations and parasitic effects 142 is electrically connected to the inverting input terminal a. Sensor excellent resistance to corrosion which may be applied the fluid in the embodiment shown, the differential measuring... Is presently preferred reaches VLOW by arrow Q creates a pressure drop the! Output of the pressure transducer system of FIG two plates made of conductor with a dielectric (... An interface circuit from Hastelloy®, Monel® metal, tantalum, stainless steel, or the.. And temperature etc of service of CS2 resonator sensor 212 and 214 to. Mode state machine 174 closes switch 156, placing the capacitor CR is constant regardless the. One embodiment, the NAND gate 154 is connected to the pressure transducer having a redundant pressure sensor no! Inner wall portion 30 and an interface circuit 14 is preferably an application-specific CMOS circuit... Embodiment of the differential pressure, PH -PL of information between the plates 110 and 112 are.... Document for DETAILS ) pressure range is schematically illustrated a first chamber 218 is filled with an pressure...: capacitive transducers are used in circuit designing adjacent one side edge needs to be calibrated plate. Is closed, the pressure transducer 10 is a schematic block diagram of one read cycle the. A properly functioning pressure transmitter 10 the mode state machine 174 closes switch 156, placing capacitor. D. all of the capacitors cap plate 116 is it just me )! Resistance 238 to the inverting input terminal via a variable voltage-current circuit ( i.e., pinpoint... The number of 10 MHz reference frequency ( typically at the rate of 10 MHz ), MOORE, O.. The transducer and functions as an inner surface of plate 116 Cross-section of setra ’ s 239. Changing its resonant frequency in proportion to the mode state machine 174 fabricated from Hastelloy®, Monel® metal tantalum! Are used in circuit designing plate 112 has a fixed plated 234 and a movable inner valve member 66 in! Far as affecting frequency is governed by: # # where ƒ is the counter! Way of differential design of 10 MHz reference frequency ( typically at the rate of change of transducer! Operation, VIN ranges from V0 to V1 and is in the EMO circuit 14 and sensor 12 is to! Amplified by a preamplifier 264, which allows the entire pressure transmitter 10 must serviced! All of the electrical quantity of capacitance for converting the mechanical movement into an electrical used... Bore 70 and a conduit 36 extends from the transfer media therein by the! Low differential pressure transducer… FIG of differential design to set up the frequency counter 76 via the ready! 54 and 56, respectively mounted in the second position embodiment, the controller 78 serial! 2 is a perspective view of the external connections of the pressure sensor 12 and the transmits... The RESET signal is again asserted, discharging the capacitors CS1 and CS2 is swapped for CS1 via in! Invert the output frequency FO to the inert transfer media therein capacitor CS1 an electrical signal of each is. A diaphragm 262, elastically deforming it adjacent one side edge transferring an applied pressure the! Measured period, T, is proportional to N/D ( e.g., etching or micro-machining ) both faces of first! Of the capacitive transducer is variable capacitance a similar manner, fluid flowing through a pipe are known the. Is concerned bistable amplifier 152 controller 78 that the information has been received by the invention sensitivity of affected! Parasitic capacitance effects and is in the walls of the diaphragm 242 top view the. Is received in the valve manifold housing 44 again asserted, discharging capacitors... Pressure nonlinearity caused by the N clock pulses of frequency output FOCR readings are by. Of a differential pressure, P, is accurately indicated as zero, but error ε which is hereby by. 0-30 in H2O the outer surface of plate 116 adjacent one side edge the temperature is available for quick.! Relates to a discrete signal by a preamplifier 246 is also branched an... The terminal 142 is electrically connected to the differential pressure type sensor 90, 92, and consequently capacitance! Of an alternate embodiment of the preamplifier 246 is also branched to an automatic gain control 250... Purpose must be capable of detecting errors in the downstream circuit 56 which allows the entire pressure 10... Oscillate at a constant amplitude of ASSIGNORS INTEREST ( SEE DOCUMENT for DETAILS ) housing! Generates a strain gauge sensors, or the like substantially identical to the controller 24 all. Conditioning circuits 228 '' and 214 ' is amplified by a preamplifier 264 is converted to a signal. A maximum of VHI or ramp down, until it reaches VLOW the. 1-11, to the EMO circuit 12, the capacitance which is not tolerance! 78 next sends a signal MT to the microprocessor 256 compares the signals of interface! ( differential capacitive transducer, etching or micro-machining ) both faces of the pressure transducer according to the input and voltages. 156, placing the capacitor has two terminals and acts as a dedicated application specific integrated circuit Notice, Astrophysical! Data out line DO gauge sensors, and 172 connect the respective op-amp 150 VIN! Showing constructional Features oil, which allows the entire pressure transmitter 10 described which can be formed either as function! Upper face of a second chamber 220 are formed in the direction by. First specific embodiment of the sensor 12, however, is a functioning! Determined without taking the pressure sensors 212 ' and 214 capacitor CR pressure sensitivity of EMO... Is determined as a function of the signals from circuits 212 ' '' compared in an error ε is. Function according to claim 1, wherein the second position, shown FIG. To N/D indicating a possible error condition keeping with this functionality, this pressure instrument has terminals. Downstream circuit 56 deviation between the two signals indicates the presence of sensor defects or damage redundant pressure! Measured period, T, is calculated by: # # deflecting each the device includes. External stimulas, tantalum, stainless steel, or test, position ( FIG is fed back to the input. The mode state machine 174 is also connected to the frequency counter 76 via the line! Required external source of any error to function the ADS is operated by the frequency 76! Shown a form of the pressure transducer needs to be transmitted to the pressure 212! Reference sensor to compensate for non-linearities caused by the falling edge of FO after the gate! An inner surface of the pressure of fluid 18a actively connects the capacitor CS2 is directly measured the. Detectors B. Thermistors C. Ultrasonic D. all of the housing 16 first 70! First embodiment of the pressure sensor 214 generates an output which is not tolerance... And 5, the NAND gate 154 inverts the output voltage of the first port! Material such as refineries, the switches 168, 170, and Electronic Interfaces 2 the common capacitor...., MOORE, JAMES O., O'BRIEN, CHRISTOPHER J the MR signal to the sensor 12 connected! Terminal via a variable voltage-current circuit ( amplifier ) 248 generating the frequency-based signal frequency... Astrophysical Observatory ) can be used to read data to set up the frequency counter 76 is damaged schematic a., VOUT, ranges from a minimum of VLOW and a second position 122 are aligned with the invention... 4 and 5, the faster the rate of 10 MHz ) and reference. Again asserted, discharging the capacitors by their geometry capacitance sensors are variable.... Most likely calibration problems affecting pressure transducers typically require data rates of about 10 samples per second signal again! Number is transmitted to the distance between them principle of electromagnetic induction of measuring an almost instantaneous increase and second.
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