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A good way to verify the stability of a pressure transducer is to periodically check the output at zero pressure input. With a gage-type transducer, this is easily accomplished by applying the same pressure to both the pressure input and the reference sides of the transducer, simply by laying the transducer on a table with nothing attached to the pressure input! However, checking the zero on a sealed gage transducer is a bit more difficult, since the reference side of the sensing diaphragm is sealed under hard vacuum. When a sealed gage unit is calibrated at the factory, the zero pressure output is set to correspond to one standard atmosphere, or 14.696 PSIA (a.k.a. 1013 millibars, or 29.92 inches of mercury.) So to check the zero on a unit of this type, one must control the input pressure to exactly 14.696
PSIA, or, one can call the local weather service and get the current barometric reading (in units of
millibars), then calculate what the transducer zero output should be by the following formula:
 return to KPSI Level and Pressure Transducer Application Notes |
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