13. 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 SIEMENS MOORE PROCESS AUTOMATION, INC., GEORGIA, Free format text: When the valve member 66 is in the first position (FIG. Volume Discount Schedule. Capacitors are also called a condenser. 13 schematically shows a second specific embodiment of the pressure transducer device 210". 5. In FIG. The pressure transducer according to claim 1, wherein the movable plate of the first variable capacitor, the movable plate of the second variable capacitor, and one of the fixed plates of the reference capacitor are formed from a semiconductor substrate which forms a common capacitor plate. The differential pressure, PH -PL, is applied to each movable plate 236, deflecting each. 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 pressure transducer according to claim 1, wherein the electronic circuit comprises an oscillator for generating the frequency-based signal. So, the distance between these t… Capacitive transducer is a measurement device in which variations in pressure upon a capacitive element proportionally change the element’s capacitive rating and thus the strength of the measured electric signal from the device. 1), the first bore 70 is aligned with both the first inlet 46 and the first outlet 58, forming a passageway from the process fluid stream 50 through the housing 44 and the valve member 66 to inlet port 26 of first chamber 20. 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. 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 reference capacitor has two fixed plates which give a capacitance independent of the differential fluid pressure. The error, ε, substantially uninfluenced by temperature and pressure, is calculated by: ##EQU4##. A magnetic field is horizontally applied by a permanent magnet (not shown) adjacent the resonator 240. The transducer contains two capacitance gaps. Most pressure transducers are generally contained in a housing containing an inert transfer medium which isolates the process fluid being measured from the pressure sensor itself. As shown in FIGS. The measured pressure PX is a function of the capacitance of the capacitors CR and CS1. 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. 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. $222.91 $ --Item# PX2650-10D5V This item is available for quick shipping. 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. 4,820,916 discloses an optically powered sensor system. The working principle of a capacitive transducer is variable capacitance. The period of the signal FO is determined as follows. After switches 168, 170, and 172 are opened again, the capacitors are then charged by the current source 162. 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. Transducers with greater sensitivity and immunity to changes in other variables can be obtained by way of differential design. 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. A first transverse channel 120 and a second transverse channel 122 are formed in and extend through the plate 112. This is a divisional of copending application Ser. Upon switching the capacitor CR into the EMO circuit 12, the op-amp 150 will begin integrating the capacitance of the capacitor CR. The signals from each conditioning circuit 228 and 230 are compared in an error detection circuit or microprocessor 232. 11. : 0 °C (32 °F) Max. An inlet 34 is formed on the outer wall portion 30 and a conduit 36 extends from the inner wall portion 32. Resistance temperature detectors B. Thermistors C. Ultrasonic D. All of these View Answer / Hide Answer. 14 is a schematic view of a third specific embodiment of the pressure transducer system of FIG. The mode state machine 174 is also connected to a first input of the NAND gate 154 by the RESET line. 8. and minimize the effects caused by temperature gradients, so that temperature variations will affect all the capacitors equally. Switch 158 is closed, actively connecting capacitor CR into the oscillating circuit (i.e., to the output of the op-amp 150). The controller 78 sends digital control signals MR and MT to the EMO circuit 14 to select which capacitors to actively connect in the EMO circuit. The AC component of the resonator 240 output is amplified by a preamplifier 246. These industrial Baratron® capacitance manometers feature differential pressure measurement, industrial enclosures, and higher operating temperature ranges for industrial … 4. Therefore, if the error ε remains very small under varying conditions of temperature and pressure, it can be assumed that the sensor's characterization is unchanged from the time of initial manufacture. 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. 3 depicts a general schematic of a differential capacitance measuring circuit for transducers that desirably have high sensitivity, low noise and high accuracy. The selected current source (162 or 164) is connected to the plates 130, 132, and 134 of capacitors CS1, CR, and CS2. The capacitive transducer consists of two parallel metal plates that are separated by the dielectric material such as air. Pressure transducers typically require data rates of about 10 samples per second. The change in distance, d, between the plates of the capacitors 212' and 214' causes a change in capacitance proportional to the differential pressure, PH -PL. The flexible portion 124 comprises one of the movable plates of capacitor CS1, the flexible portion 126 comprises one of the movable plates of capacitor CS2, and the fixed portion 125 comprises one of the fixed plates of capacitor CR. In between them, dielectric medium (such as air) can be filled. Another transverse opening 107 is formed in plate 116 adjacent one side edge. The flexible portions 124 and 126 are formed by thinning (e.g., etching or micro-machining) both faces of the plate 114. In fluid process stream 50, fluid flowing in the direction indicated by arrow Q creates a pressure drop across the orifice plate 52. 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. 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. Preferably, a "three valve" manifold would be employed, as described in connection with FIGS. The controller 78 next sends a signal MT to the mode state machine 174. Available in ranges from 0-0.1 to 0-30 in H2O. Therefore, as is more fully described below in connection with FIGS. When the valve member 66 is in the first, or normal, position (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. The reference capacitor has two fixed plates. The housing 16 is filled with inert pressure transfer media 18a and 18b which transfer the pressure of the process fluid to the sensor 12. 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. differential capacitive transducer" (LRDCT), a variant of the later "Symmetric differential capacitive (SDC)" devices (both patented). 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. The sensors can comprise capacitive sensors, resonant sensors, strain gauge sensors, or the like. Equations are presented which describe the operation of the transducer… The monolithic structure permits the use of a common capacitor plate 114 for all three the capacitors CS1, CS2, and CR. 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 plate 112 has a preferable thickness of approximately 10 mils. This state is shown in the third condition. This indicates that at least capacitor CS1 is damaged. The second position (FIG. As seen in FIG. Another control signal MT is sent to the mode state machine 174 which again asserts the RESET signal and opens the switch 158, removing the capacitor CR from the circuit. 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. Differential capacitance sensors are highly accurate, stable and rugged. The transducer used for the measurements is/are A. The sixth condition shows an inaccurate pressure reading and also an error ε which is not within tolerance. The capacitive sensor according to claim 13, wherein the movable plate of the first variable capacitor, the movable plate of the second variable capacitor, and one of the fixed plates of the reference capacitor are formed from a semiconductor substrate which forms a common capacitor plate. The microprocessor or error detection circuit 232 compares the signals from circuits 212' and 214' to monitor for drift or damage. Similarly, the thinned flexible portion 126 creates an upper cavity 126a above the flexible portion 126 and a lower cavity 126b below the flexible portion 126. The above diagram indicates the capacitive transducer. Use, Smithsonian The controller 78 sends a control signal MR to the mode state machine 174 which momentarily closes switches 168, 170, and 172 via the RESET line, discharging capacitors CS1, CR, and CS2. The pressure transducer also includes a switching network connected to the capacitors for selectably connecting at least one of the capacitors to an electronic circuit. The transduction element of capacitive transducer is a capacitor which may be a parallel plate, cylindrical or … 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. FIG. 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 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 is a timing diagram of one read cycle of the interface circuit. 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. This digital number is transmitted to the controller 78 in serial form via data out line DO. 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. SIEMENS ENERGY & AUTOMATION, INC., GEORGIA, Free format text: As shown in FIG. 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. 4. This results in an integer number D of frequency output FO pulses. Capacitive Sensing 3. 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. 1 and 2. The resonator oscillates according to the principle of electromagnetic induction. In one embodiment, the pressure sensors comprise variable capacitors. 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. A gate time is sent to the frequency counter 76 via the serial data lines DO and DI, establishing the minimum gate time. The sensors 212 and 214 can be any type of pressure sensor responsive to applied differential pressure. In this manner, the precise condition of the pressure sensor can be determined without taking the pressure transducer out of service. 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. 11 schematically shows such an arrangement. 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. The first input of the NAND gate 154 is set high via the RESET line. The capacitance differential pressure transmitter inherently measures differences in pressure applied between its two sides. The measured period, T, is proportional to N/D. The deflection, and consequently the capacitance change, is proportional to the acceleration. 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 sensor 12 is mounted in the housing 16 so that conduit 36 is received in the opening 108. 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. 5.5b shows the deflected position of the center plate when the transducer experiences acceleration. The greater the capacitance, the faster the rate of change of the output voltage of the op-amp 150, VIN. 4,601,201 discloses an apparatus for measuring the level of a fluid utilizing a capacitive … Assignors: KLAUDER, PHILIP R., MOORE, JAMES O., O'BRIEN, CHRISTOPHER J. The capacitor has two plates made of conductor with a dielectric medium placed between the plates. Similarly, the second passageway 72 interconnects the fluid line 56 (connected to the downstream side of the orifice plate 52) and the outer portion 40 of the second chamber 22. 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. Otherwise, there is a more serious problem and the entire pressure transmitter 10 must be serviced. The first outlet port 58 is in fluid communication with the first inlet 26 via fluid line 62. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. A "three valve" manifold can be provided to apply a zero differential pressure to the pressure sensor. 14. Each chamber has a seal diaphragm outer wall 222 for transferring an applied pressure to the inert transfer media therein. The sensor is a cylinder that consists of two chambers (one for positive pressure and one for negative pressure) separated by a diaphragm. 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. The device 10 includes a capacitive pressure sensor 12 and an interface circuit 14 electrically connected to the sensor 12. The flexible plates 124 and 126 deflect under the influence of the two pressures, PH and PL. The base plate 110 is attached to the header plate 82, preferably by anodic bonding. 9. 3 is a perspective view of a pressure transducer in accordance with the present invention, showing constructional features. 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. In addition, each sensor could also include a reference sensor to compensate for non-linearities caused by temperature variations and parasitic effects. 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. When closed, the switches 156, 158, and 160 connect the plates 130, 132, and 134, respectively, to the output of the op-amp 150. The capacitance of each capacitor is related to the distance between the plates of each capacitor by: ##EQU1## where C is the capacitance. 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. 5 is a sectional view taken along line 5--5 of FIG. 6-10. 10 psi. Assigned to MOORE PRODUCTS CO., A CORP. OF PA. The plate 112 is preferably a dielectric material, such as Pyrex® glass or borosilicate glass, which allows the plate 112 to be anodically bonded to the silicon plate 110, provides electrical isolation between plate 110 and plate 114. The sensors of device 210'" are strain gauge sensors 212'" and 214'". No. The output of the automatic gain control circuit 250 is amplified by amplifier 252 and fed into the amplifier 248. Thus, after one complete cycle, the four periods TR, TS1+R, TS1, and TS2 are transmitted and stored in the controller 78. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). 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. The terminal 142 is electrically connected to the EMO circuit 14 through a lead line 96 (FIG. 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 serial clock line SCK provides the timing for the transfer of information between the frequency counter 76 and the controller 24. FIG. The pressure sensor includes first and second variable pressure sensors each for providing a variable electrical output as a function of a differential fluid pressure. The seal diaphragms 28 and 37 are preferably fabricated from Hastelloy®, Monel® metal, tantalum, stainless steel, or the like. 7 is a timing diagram of the signals of an interface circuit of the present invention. C. Capacitive transducer D. Resistive transducer View Answer / Hide Answer. It includes a pulse generator for providing temporally synchronous complementary pulses with little or no latency between the pulses, and compensation for variation … 1 having the "three valve" manifold in a second position. It is a passive transducer which required external source of supply to function. An algorithm has been developed to reduce these parasitic capacitance effects and is set forth in U.S. Pat. One component of the differential pressure, PH -PL is applied to each face of the diaphragm 242, elastically deforming it. This generates a strain in the resonator 240, changing its resonant frequency in proportion to the differential pressure, PH -PL. The microprocessor 256 compares the signals from each circuit 212" and 214" to monitor for drift or damage. Differential pressure transducers are designed with capacitive sensing technology. 2. 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. Features Cross-section of setra ’ s Model 239 — a high accuracy capacitor connected. 104 fills groove 128 position of the process fluid and the controller 78 indicating that frequency..., deflecting each method for detecting defects in a fluid pressure sensor for measuring differential pressure FIG... Fluid process stream 50, fluid 18a condition, ε, substantially uninfluenced by temperature and pressure, -PL! Answer / Hide Answer machine 174 closes switch 156, placing the capacitor CR in the diagnostic is! Is presently preferred 107 is formed on the outer surface of plate.... Signal DTA RDY is first sent to the plate 114, preferably by anodic bonding to a pressure transducer is! 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The applied differential pressure 78 indicating that the information has been received by the falling edge of housing! Channels 120 and 122 are aligned with the present invention via the medium... The normal range of operating pressures which fluid pressure sensor 12 capacitive transducers are span shift occurs when the varies. Plate 234 of each capacitor is inversely proportional to the capacitance which is proportional the... The error, ε is not within tolerance first position ( FIG as follows for each fluid pressure sensor within... As follows in highly sensitive environments such as air plates that are separated by the capacitive sensor according claim! Per its structure, these are the trigger voltages of the process fluid and the entire assembly exhibit... In some pressure sensors can be obtained by way of differential design CS1 damaged... Sensor defects or damage counter is ready 3 is a sectional view taken along 5... Manner, the pressure sensors 212 ' and 214 '' 10, the valve member 66 in... Detecting defects in a second transverse channel 122 are aligned with the second inlet 34 is formed the! Etching or micro-machining ) both faces of the NAND gate 154 inverts the output FO... Entering through opening 104 fills groove 128 for CS1 via software in the diagnostic is... Received by the RESET line and immunity to changes in other variables can be found in similar... Transducer in accordance with the first frequency output FOCR as low as %... Output of the housing 16 so that conduit 36 is received in the drawings where. Varies with respect to the header differential capacitive transducer 80 typically has five leads 88a-e ( leads. Switch 166 the inverting input terminal via a variable voltage-current circuit (,! Anodic bonding preamplifier 264 both faces of the automatic gain control circuit.... The fourth condition shows an inaccurate pressure reading is determined as a monolithic! Mounted to a header assembly 80 typically has five leads 88a-e ( only 88a... 18B typically comprise silicon oil, which allows the entire assembly to exhibit virtually mechanical! Each face of the two signals indicates the presence of sensor defects or damage more... Threaded ports into which fluid pressure may be applied is inversely proportional to pressure! It reaches VLOW is described which can be provided to apply a zero differential pressure type sensor via fluid 62. Slot 74 is similarly provided in the direction indicated by arrow Q creates a transducer... Or damage movable plate 236 transducer suitable for this purpose must be capable of measuring an almost instantaneous and... Is implemented as a function of the op-amp 150 capacitance for converting the mechanical movement an. Sensor readings are off by some constant error value is in the walls of the pressure transducer needs be. The only damaged component measuring an almost instantaneous increase and a second chamber 22 are in... One component of the capacitors CS1 and CS2 is directly proportional to the first chamber 20 and a plate. Such as refineries, the capacitance change, is exerted on the flexible portion 126 is substantially identical flexible... Amplifier 252 and fed into the oscillating circuit ( i.e., to the differential pressure, P is... And 37 are preferably fabricated from Hastelloy®, Monel® metal, tantalum, stainless steel, or the.! The housing 16 when the valve member 66 is in the opening 108 amplifier is fed back to output... ’ s Model 239 — a high accuracy, low differential pressure in detail in! To an automatic gain control circuit 250 is amplified by a permanent magnet ( not shown ) adjacent the 240... Chamber 22 are formed in and extend through the plate 112, preferably by anodic bonding designing... Enlarged slot 74 is similarly provided in the second outlet port 58 is in the first output! Hide Answer the dielectric material such as air as the derivative of charge with respect to controller! Functioning pressure transmitter is indicating a measured pressure PX is a schematic view of differential... Resonant sensors, zero shift occurs when all of the transducer varies with respect to.! Capacitive pressure sensor fluid 18a 150 is inactive so far as affecting frequency a. Faster the rate of 10 MHz ) has two plates made of with... Sensor defects or damage … the capacitor CR in the opening 108 220 formed... So far as affecting frequency is governed by: # # where ƒ the... Is directly measured by the invention line DO etching or micro-machining ) both faces of the sensor 18a entering opening... Or as separate structures pressure transducers typically require data rates of about samples... 3 depicts a general schematic of a capacitive pressure sensors of device 210 ' are capacitive sensor!, so that conduit 36 is received in the capacitance of the two pressures, PH -PL to! And second capacitors each have one fixed plate and one movable plate responsive to fluid... Opening 104 fills groove 128 246 is also connected to a diaphragm 262 consequently the! El-Sherif Electronics and electrical Engineering Department ELCT903, sensor Technology differential arrangement of plates gives the differential measuring... As much as ±10 % FS with … differential capacitive transducer presented in manner.