Capacitive gage pressure sensor with vacuum dielectric
A gauge pressure sensor and sensor technology, applied in the direction of measuring fluid pressure, instruments, and measuring fluid pressure through electromagnetic components, can solve the problems of limiting the ability of the sensor to use, temperature instability errors, etc.
Active Publication Date: 2012-02-15
ROSEMOUNT INC
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Problems solved by technology
Other configurations allow the atmosphere (air) to become a dielectric material, which can cause temperature instability errors and limit the sensor's ability to be used in corrosive environments
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[0011] The disclosed embodiments address difficulties with existing capacitive pressure sensor configurations that measure gauge pressure of a process. Gauge pressure is zero referenced to ambient air pressure. In other words, the gauge pressure of the process is equal to the absolute pressure measured in the process minus the atmospheric pressure in the surrounding area.
[0012] The disclosed embodiments provide measurement of gauge pressure without the use of an auxiliary barometric pressure sensor, while still using a vacuum dielectric to reduce temperature instability and / or provide other advantages over existing capacitive gauge pressure sensor designs. Advantage.
[0013] figure 1 An example capacitive gauge pressure transmitter or field device 100 is shown, using which the disclosed embodiments are useful. figure 2 A portion of pressure transmitter 100 is shown in greater detail. In general, pressure transmitter 100 includes a transmitter body 105 coupled to a sen...
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A field device (100) includes a capacitive gauge pressure sensor configured to measure a gage pressure of a process media, A sensor body (110) of the pressure sensor includes first and second chambers (112, 113). The second chamber (113) is under vacuum and forms a vacuum dielectric for the pressure sensor. An atmospheric reference port (180) is formed in the sensor body (110) and maintains the first chamber (112) in equilibrium with ambient atmospheric pressure. A process media inlet port (125) of the sensor is configured to couple to a process media source (120). The sensor includes a conductive deflectable diaphragm (130) between the second chamber (113) and the media inlet port (125). A capacitive plate (140) is disposed in the second chamber (113) in relation to the diaphragm (130) such that deflection of the diaphragm (130) generates a change in capacitance. The field device (100) also includes sensor circuitry (185) which generates a sensor signal indicative of the gage pressure of the process media (12O) and transmitter circuitry (190) which transmits information relative to the sensor signal over a process communication loop (195).
Description
Background technique [0001] Field devices (eg, process variable transmitters) are used in the process control industry to sense process variables remotely. A field device or process variable transmitter includes a capacitive pressure sensor for monitoring process pressure. [0002] Various dielectric materials are used in these capacitive pressure sensors. For example, fluid-filled configurations are sometimes employed in which oil or other fluids are used as the dielectric material. In other configurations, it is desirable to use a vacuum as the dielectric material. Vacuum dielectrics can have less complex construction, can reduce cost, be oil-free, can be more precise, and / or can be more stable. However, due to the vacuum dielectric construction, these sensors typically only measure absolute pressure, not gauge pressure of the process (eg, process pressure relative to local pressure such as the surrounding atmospheric pressure). Gauge pressure is sometimes called "gauge"...
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IPC IPC(8): G01L9/00
CPCG01L9/0072
Inventor 戴维·A·布罗登
Owner ROSEMOUNT INC