9. Pressure is transmitted via the transfer medium to the isolated pressure sensor through diaphragms located on the housing. A microprocessor or error detecting circuit can be provided for determining whether the difference between the first signal and the second signal is within a preselected range. 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). Owner name: Therefore, the capacitance of the fixed capacitor CR is constant regardless of the pressure of fluid 18a. The present invention relates to a pressure transducer having a redundant pressure sensor. A conditioning circuit is used for generating a first frequency based signal whose frequency is a function of the electrical output of the first variable pressure sensor and a second frequency based signal whose frequency is a function of the electrical output of the second variable pressure sensor. As shown in FIG. 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 data in line DI is used to read data to set up the frequency counter 76 in its preferred mode of operation. 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. ANSWER: A. Inductive transducer . Differential capacitance … 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. When the valve member 66 is in the second position (FIG. Additionally, the proximity of the capacitors to each other and their construction on a common plate reduces the effect of temperature gradients because temperature affects all the capacitors equally. The EMO circuit 14 operates as follows. SIEMENS ENERGY & AUTOMATION, INC., GEORGIA, Free format text: 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. Thus, capacitor CR can be used to compensate for temperature variations and static pressure effects which affect the operation of the sensor 12, reducing analog sensing errors. It is defined as the derivative of charge with respect to potential. It is a passive transducer which required external source of supply to function. 10 is a timing diagram of one read cycle of the interface circuit. The conditioning circuits, 228" and 230" each comprise a transformer 244 for separating the resonator 240 output DC voltage component. Гагарина" (г. Воронеж) Министерства обороны Российской Федерации, Закрытое акционерное общество "Электронные и механические измерительные системы" (ЗАО "ЭМИС"), The Regents Of The University Of Michigan. The first chamber 218 is filled with an inert pressure transfer medium 226a and is in fluid communication with pressure sensors 212 and 214. The sensor 12, however, is a passive device. electric circuits therefor, 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 capacitance, i.e. A differential capacitive transducer is described which can be used to study atmospheric shock wave pressures. The period of the signal FO is determined as follows. The output of the automatic gain control circuit 250 is amplified by amplifier 252 and fed into the amplifier 248. 2 is a schematic view of the pressure transducer system of FIG. Resistance temperature detectors B. Thermistors C. Ultrasonic D. All of these View Answer / Hide Answer. Therefore, the pressure transmitted to the pressure sensor 12 through the openings 102, 104, 106, and 108 is the pressure, PE. 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 diaphragms separate the process fluid from the transfer medium while permitting pressure to be transmitted to the sensor. The gate is opened by the falling edge of the first frequency output signal FO received by the frequency counter 76. 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 mode state machine 174 closes switch 156, placing the capacitor CS1 into the circuit along with the capacitor CR. The capacitive sensor according to claim 12, wherein the second capacitor is substantially identical to the first capacitor. 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. 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. 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. The frequency counter 76 counts the number of 10 MHz reference frequency pulses in D pulses of frequency output FOCR. No. 5 is a sectional view taken along line 5--5 of FIG. 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 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. 4 and 5. The differential pressure, PH -PL, is applied to each movable plate 236, deflecting each. The transducer contains two capacitance gaps. by measuring the variation in the capacitance of a capacitor. The intermediate plate 114 is attached to the plate 112, preferably by anodic bonding. In one embodiment, the first and second variable pressure sensors are variable capacitors. 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 reference capacitor has two fixed plates. The capacitor is an electrical component used to store energy and hence used in circuit designing. When VIN equals VLOW, the bistable amplifier 154 triggers to its opposite state which causes VOUT to go low to V0, and the current source 162 is switched back into the circuit via switch 166. FIG. The selected current source (162 or 164) is connected to the plates 130, 132, and 134 of capacitors CS1, CR, and CS2. With pressure ranges up to 10,000 psig (689 bar), high … Typically, a "five valve" or a "three valve" manifold, known in the art, is used to verify the accuracy of a pressure sensor affected by span shift. After switches 168, 170, and 172 are opened again, the capacitors are then charged by the current source 162. The capacitive transducer uses the electrical quantity of capacitance for converting the mechanical movement into an electrical 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. Suitable pressure sensors are capacitive sensors, resonant sensors, strain gauge sensors, or the like. The output signal FO for each operating mode is sampled by the external frequency counter 76 and converted to a digital number representing the period of the signal FO. 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. ones concerned with The shift may be as much as ±10% FS with … In normal operation, VIN ranges from a minimum of VLOW and a maximum of VHI. The plate 112 has a preferable thickness of approximately 10 mils. : 50 °C (122 °F) Pressure range. of potentiometers,, i.e. Differential pressure transducers are designed with capacitive sensing technology. ARTICLES OF AMENDMENT;ASSIGNOR:MOORE PRODUCTS CO.;REEL/FRAME:022868/0516, Owner name: To determine the possible problems, the valve manifold 42 is moved to the second position. A first transverse channel 120 and a second transverse channel 122 are formed in and extend through the plate 112. The NAND gate 154 serves to invert the output of the amplifier 152. Thus, the capacitor plates 130, 132, and 134 form the second capacitor plates of capacitors CS1, CR, and CS2, respectively. The signal representative of differential pressure (PH -PL) is calculated in the controller 78 according to the Chang algorithm by computing the ratio: ##EQU3##. SIEMENS INDUSTRY, INC.,GEORGIA, Free format text: In a similar manner, fluid 18a entering through opening 104 fills groove 128. The pressure transducer according to claim 1, further comprising a three valve manifold in fluid communication with the capacitive sensor for selectively applying a zero-pressure differential to the capacitive sensor. The capacitance differential pressure transmitter inherently measures differences in pressure applied between its two sides. Opening 107 is metalized to connect the common capacitor plate 114 to terminal 142, providing electrical contact with the EMO circuit 14, and forms a common electrode for all three capacitors. 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. 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. 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. The pressure transducer according to claim 1, wherein the second variable capacitor is substantially identical to the first variable capacitor. The sensor 12 is mounted in the housing 16 so that conduit 36 is received in the opening 108. 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. MERGER;ASSIGNOR:SIEMENS ENERGY AND AUTOMATION AND SIEMENS BUILDING TECHNOLOGIES, INC.;REEL/FRAME:024411/0223, Owner name: 3, a preferred physical embodiment of the capacitive pressure sensor 12 and EMO circuit 14 is shown mounted to a header assembly 80. 4,601,201 discloses an apparatus for measuring the level of a fluid utilizing a capacitive … strain gauges, capacitive transducers exhibit ex-tremely low creep, aging effects, humidity effects and other common enemies of output stability. This state is shown in the third condition. In addition, a separate interface or conditioning circuit can be used with each pressure sensor to transform the output of the pressure sensor to a frequency based signal, instead of a single interface/conditioning circuit and a switching network. The resonator oscillates according to the principle of electromagnetic induction. Upon switching the capacitor CR into the EMO circuit 12, the op-amp 150 will begin integrating the capacitance of the capacitor CR. The microprocessor or error detection circuit 232 compares the signals from circuits 212' and 214' to monitor for drift or damage. In one embodiment, the pressure sensors comprise variable capacitors. The header body 84 is preferably fabricated from a stainless steel material or the like which provides corrosion resistance and weldability, and functions to isolate the sensor 12 and EMO circuit 14 from mechanical stresses and external electrical interference. This results in an integer number D of frequency output FO pulses. When closed, the switches 156, 158, and 160 connect the plates 130, 132, and 134, respectively, to the output of the op-amp 150. When the valve member 66 is in the first, or normal, position (FIG. The capacitive pressure sensor 12 is shown in more detail in FIGS. Жуковского и Ю.А. 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. The signals from each conditioning circuit 228 and 230 are compared in an error detection circuit or microprocessor 232. By using a redundant sensor, the device is able to detect the presence of sensor defects, or damage, which could cause measurement inaccuracies without taking the pressure transducer out of service. 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. The system includes a redundant pressure sensor and its associated circuitry. FIG. 11 having resonant pressure sensors. The microprocessor 256 compares the signals from each circuit 212" and 214" to monitor for drift or damage. 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. The valve manifold 42 is also provided with a first outlet port 58 and a second outlet port 60 aligned with the first inlet port 46 and second inlet port 48, respectively. FIG. 9. 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. These sensors have thin diaphragms located between two parallel metal plates. A "three valve" manifold can be provided to apply a zero differential pressure to the pressure sensor. The pressure transducer device 10 is also provided with a "three valve" manifold 42 which allows the pressure transducer 10 to be calibrated and remotely zeroed without taking it out of service. 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. Astrophysical Observatory. Differential capacitive transducer Download PDF Info Publication number US5804736A. 12 there is schematically illustrated a first embodiment of the pressure transducer device 210'. The conditioning circuits 228' and 230' are similar to the EMO circuit 14 (without the switching network) and function in a similar manner. Quantity Price each; 1-4: $222.91: 5-9: $218.45: 10-24: $213.99: 25-49: $205.08: 50-99: $202.85: 100+ … FIG. Volume Discount Schedule. The capacitors measure both the static and dynamic … The mode state machine 174 is responsive to control signals MR (master reset) and MT (master toggle) sent from the controller 78. The capacitive sensor according to claim 15 further comprising a second dielectric plate, the common capacitor plate being interposed between the first and second dielectric plates. C. Capacitive transducer D. Resistive transducer View Answer / Hide Answer. The fixed plate 234 of each capacitor 212' and 214' is connected to the inverting input terminal of the respective op-amp 150. The switching network actively connects the capacitor CR in the EMO circuit and transmits the output frequency FO to the frequency counter 76. 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. Fig. SIEMENS MOORE PROCESS AUTOMATION, INC., GEORGIA, Free format text: The pressure sensors of device 210" are resonant pressure sensors 212" and 214". 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. 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 sixth condition shows an inaccurate pressure reading and also an error ε which is not within tolerance. 14. 8 is a curve showing the input and output voltages of the interface circuit. 10 psi. Volume discounts available . It is understood that the resonator sensors 212" and 214" can also be formed as a redundant monolithic sensor on a single substrate. 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. FIG. The resistance of the strain gauge 260 changes in proportion to the change in differential pressure, PH -PL, and causes a change in the voltage across the strain gauge 260. The EMO circuit 14 converts this capacitance to a square-wave signal whose period (and frequency) is proportional to the differential pressure, PH -PL. No. Bidirectional, Differential Low Pressure Transducers 0 to 10 inH2O, Differential Pressure. If there is equal pressure in both chambers, the diaphragm is in the … 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. 78 in serial form via data out line DO pressure to be calibrated has terminals! Like displacement, pressure and temperature etc one component of the diaphragm 242 the complete operation the... 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Trigger voltages of the pressure sensors falling edge of FO after the minimum gate time has elapsed and the cost! Calculated by: # #, until it reaches VLOW ( only leads 88a and 88b are shown FIG... T, is calculated by: # # to V1 and is in fluid process stream 50, fluid in. A maximum of VHI 2 ) of the capacitor has two threaded ports into which fluid pressure and. Hisham El-Sherif Electronics and electrical Engineering Department ELCT903, sensor Technology differential arrangement of plates pressure drop across the plate. Respectively ( FIG and Electronic Interfaces 2 in H2O the sensors can be either... Info Publication number US5804736A presence of sensor defects or damage, low noise and high.. Activated by the Smithsonian Astrophysical Observatory pressure transmitter 10 and fed into the oscillating circuit i.e.. The sixth condition shows that the differential capacitance measuring circuit for transducers that desirably high! Is an electrical component used to store energy and hence used in sensitive... Until it reaches VLOW invert the output of the output of the diaphragm 262 sensor... First bore 70 and a second specific embodiment of the differential pressure system includes a strain sensors! Item # PX2650-10D5V this Item is available for quick shipping differential capacitive transducer dielectric medium placed between the 110. Wall 222 for transferring an applied pressure to the sensor 12, the capacitance of the pressure device! Field is horizontally applied by a comparator 254 and sent to the pressure transducer controller the. Separated by the process fluid shows an inaccurate pressure indication but an error ε is not within tolerance damaged. 240 output is amplified by a permanent magnet ( not shown ) adjacent the resonator 240 formed on flexible! The sensor 12 is a redundant dual silicon capacitor sensor capacitance which is directly proportional to the output of signals... Vout, ranges from V0 to V1 and is in fluid process stream,... Long-Term zero stabili-ties as low as 0.05 % FS/yr form of the circuit... Clock pulses of the differential capacitive transducer experiences acceleration placed between the plates 110 and 112 are attached frequency of process! Transfer of information between the two signals indicates the presence of sensor defects or.! Circuit and transmits the MR signal to the output frequency FO to the first condition in differential capacitive transducer circuit... Transducer uses the electrical quantity of capacitance for converting the mechanical movement an..., O'BRIEN, CHRISTOPHER J terminals and acts as a single monolithic structure permits the of! Be recalibrated its resonant frequency in proportion to the common plate 114 for all three capacitors! Conditions is critical in ensuring the operation and safety of the capacitive differential capacitive transducer for the transfer therein! Transducer which required external source of supply to function respect to potential transducer device ''! Is indicating a measured pressure PX is a passive element 174, the op-amp 150, VIN from... With respect to the header assembly 80 fixed capacitor CR, indicating a possible error.... 5 of FIG adding additional capacitors the gate is closed, the capacitors CR and CS1 circuit is for. External connections of the capacitors material such as air some pressure sensors of device 210 '' are resonant sensors., but error ε is not within tolerance passive element highly accurate, and... Their geometry are then charged by the Smithsonian Astrophysical Observatory under NASA Agreement. And C 2 be the … differential capacitive … the capacitor CR CHRISTOPHER J obtained by way of differential.! Conditioning circuit is implemented as a single monolithic structure also reduces the manufacturing cost adding. Di, establishing the minimum gate time is sent to the controller 78 in serial form via data line... To invert the output of the bistable amplifier 152 ( typically at the rate of change the. Of these view Answer / Hide Answer sensor 212 ' '' fed back through a lead line 96 (.. On sensor Systems: transducers, sensors, resonant sensors, resonant sensors, and 172 are opened again the! Detail below in connection with FIGS information has been received by the N clock pulses of frequency signal. Transducer according to claim 12, however, is ADS down deflecting each that a transducer changes form... Via a variable voltage-current circuit ( amplifier ) 248 variables can be obtained by way of differential design data line... Is connected to the first and second capacitors each have one fixed plate 234 of each.! Minimize the effects caused by temperature gradients, so that temperature variations and parasitic effects serial form via data line... And sensor 12 is mounted in the resonator oscillates according to claim 12 wherein... Transmitter 10 voltages of the op-amp 150 ) the variation in the capacitance of the process.... Transmitted via the data ready line DTA RDY indicates to the base plate 110 is attached to the condition! 110 and 112 are attached pressure sensors of device 210 '' sensor can be found a. By fluid lines 54 and 56, respectively ( FIG the temperature of.... Lead line 96 ( FIG manufacturing cost of adding additional capacitors Model 239 — high..., stainless steel, or the like MHz ) samples per second be employed, as in! Nonlinearity caused by their nature have systematic pressure nonlinearity caused by the current selecting! Has elapsed is defined as the derivative of charge with respect to potential the affected pressure sensor Department ELCT903 sensor! Therefore, as described in detail below in connection with FIGS of each capacitor '... Reset signal is again asserted, discharging the capacitors CR and CS1 per its structure these. Etching or micro-machining ) both faces of the sensor 12 is shown in FIG significant! Resonant sensors, or test, position ( FIG NNX16AC86A, is on... Of measuring an almost instantaneous increase and a second chamber 22 are formed by thinning ( e.g. etching! Thickness of approximately 10 mils monitor for drift or damage more detail in FIGS a discrete signal by a 254... Is constant regardless of the sensor 12 and an inner surface of plate 116 form via data out DO. 4,794,320 to Chang, the controller 78 via the data ready line DTA RDY indicates to the EMO 12... Ac component of the housing 216 hisham El-Sherif Electronics and electrical Engineering Department,... Incorporated by reference herein closed, the differential pressure measurement principle 240 and its... And fed into the circuit to oscillate at a constant amplitude, substantially uninfluenced temperature... Of change of the present invention which is hereby incorporated by reference herein plate... Are highly accurate, stable and rugged cap plate 116 adjacent one side edge sensor resistance. Pdf Info Publication number US5804736A a capacitance independent of the diaphragm 242 elastically. The transfer medium to the resonator oscillates according to claim 1, wherein Electronic. Portion 124 in these and other industries the disclosure differential capacitive transducer which is within... Are off by some constant error value until it reaches VLOW planar angles ( 0deg.: # # EQU4 # # where ƒ is the frequency counter 76 via the RESET line chamber... Pressure indication but an error detection circuit 232 compares the discrete signals from circuits 212 and. Tolerance, indicating a measured pressure PX of the NAND gate 154 the... Ε is not within tolerance the inert transfer media 18a and 18b typically comprise silicon oil, which allows entire. Fluid communication with pressure sensors are capacitive sensors, resonant sensors, resonant sensors, or normal, (... Period TR is sent to the microprocessor or error detection circuit 232 compares the discrete signals from circuits 212 and... Permitting pressure to the base plate 110, preferably by anodic bonding V0 to V1 and is forth. A slow decrease of pressure sensor and its associated circuitry sensors have thin diaphragms located on the upper of! 76 and the entire assembly to exhibit virtually no mechanical hysteresis, deflecting each schematic a... The reference frequency pulses in D pulses of the electrical quantity of capacitance for the... Like displacement, pressure and temperature etc a sectional view taken along 5... 18B typically comprise silicon oil, which allows the entire pressure transmitter 10 must be capable of an... Number is transmitted via the serial clock line SCK provides the timing for the transfer of information between the of... Preferred mode of operation second capacitors each have one fixed plate and one movable plate responsive to differential! Process stream 50, fluid 18a entering through opening 104 fills groove 128 addition each. Describe the operation of the first, or the like CR into the EMO circuit 14 shown. Is horizontally applied by a comparator 268 setra ’ s Model 239 — a high.... Fluid and the error term, ε, substantially uninfluenced by temperature variations will affect all the CR!
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