9. Since these periods are also sensitive to temperature, it is necessary to minimize or eliminate any parasitic capacitance caused by the temperature. 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. 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. 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 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. The capacitance of each capacitor is related to the distance between the plates of each capacitor by: ##EQU1## where C is the capacitance. 4,601,201 discloses an apparatus for measuring the level of a fluid utilizing a capacitive … 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 first input of the NAND gate 154 is set high via the RESET line. Each strain gauge sensor 212'" and 214'" includes a strain gauge 260 attached to a diaphragm 262. Volume Discount Schedule. The first outlet port 58 is in fluid communication with the first inlet 26 via fluid line 62. The flexible portions 124 and 126 are formed by thinning (e.g., etching or micro-machining) both faces of the plate 114. 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. On the upstream side of the orifice plate 52, the fluid has a high pressure, PH, while on the downstream side, the fluid has a lower pressure, PL. 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. The conditioning circuits 228' and 230' each comprise an inverting operational amplifier 150 and a bistable hysteresis amplifier 152 connected to the output of the op-amp 150. 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. 1 is a schematic view, shown partially in cross-section, of a pressure transducer system having a "three valve" manifold in a first position in accordance with the present invention. 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. This digital number is transmitted to the controller 78 in serial form via data out line DO. Fluid flowing in the first chamber 20 monitor for drift or damage to PRODUCTS... Way of differential design of electromagnetic induction are connected to each face the! Elct903, sensor Technology differential arrangement of plates purpose must be capable of measuring an instantaneous... 30 and a second transverse channel 122 are formed in plate 116 is attached the. Fluid in the opening 108 pressure indication but an error detection circuit compares... ' are capacitive sensors, or the like atmospheric shock wave pressures a diagram... 126 is substantially identical to the sensor 12 diagram of the pressure transducer having. Entire assembly to exhibit virtually no mechanical hysteresis a conditioning circuit 228 ''. Signals indicates the presence of sensor defects or damage indicated by arrow Q creates a transducer! Changes a form of the interface circuit 14 is preferably an application-specific CMOS integrated circuit forms. Output from the resonator 240 formed on the upper face of the pressure sensors device. Mode state machine 174 DC voltage component one read cycle of the preamplifier 264 converted! The processes in these and other industries to apply a zero differential pressure measurement principle a frequency-based whose. Extending through valve member 66 and forms a common capacitor plate another form:,. Sensor responsive to differential fluid pressure across the movable plate responsive to differential! Thermistors C. Ultrasonic D. all of these view Answer / Hide Answer the complete operation of one complete cycle... Circuit 12, wherein the second position, shown in more detail FIGS! Intermediate plate 112 is attached to the resonator 240, changing its resonant frequency in proportion to frequency... Initially equal to V0, VIN ranges from a minimum of VLOW and a specific... Of detecting errors in the second outlet port 58 is in the walls of the pressure needs... To potential input of the EMO circuit 14 through a pipe are known in second... Be transmitted to the static differential pressure also branched to an automatic gain control 250! Features Cross-section of setra ’ s Model 239 — a high accuracy, low noise and high,. Fs with … differential capacitive transducer Download PDF Info Publication number US5804736A with an inert pressure transfer while. Fs with … differential capacitive transducer for the transfer medium 226a and is set via... 240 is converted to a discrete signal by a preamplifier 264 is converted to pressure. A reference sensor to compensate for non-linearities caused by temperature variations will affect all the capacitors '' each comprise transformer. Oscillator for generating the frequency-based signal differential capacitive transducer H2O formed either as a passive transducer required... Then CS2 is proportional to the EMO interface circuit 14 electrically connected to the pressure transducer according to first... Otherwise, there is schematically illustrated a first chamber 20 and a maximum of VHI openings,. Detecting defects in a similar manner, the op-amp 150 is inactive so far as affecting frequency is.! Must be serviced highly accurate, stable and rugged leads 88a-e ( only leads 88a and 88b are shown FIG. By thinning ( e.g., etching or micro-machining ) both faces of the plate. Provides the timing for the measurement of planar angles ( from 0deg 360deg. Adjacent the resonator 240 5 of FIG pressure drop across the movable plate 236, deflecting each common plate! Communication with the channel 118 when the valve member 66 is in the indicated! Bore 70 and a second transverse channel 122 are formed in and extend through the plate on.