A portable pressure-application device has been designed and built for use in testing and calibrating piezoelectric pressure transducers in the field. The device generates pressure pulses of known amplitude. A pressure pulse (in contra- distinction to a steady pressure) is needed because in the presence of a steady pressure, the electrical output of a piezoelectric pressure transducer decays rapidly with time.

Air Is Manually Pumped into a cylinder for storage at a specified pressure. To test a pressure transducer, one presses a pushbutton to activate a solenoid valve that releases a pulse of pressurized air from the cylinder.
The device (see figure) includes a stainless- steel compressed-air-storage cylinder of 500-cm3 volume. A manual hand pump with check valves and a pressure gauge are located at one end of the cylinder. A three-way solenoid valve that controls the release of pressurized air is located at the other end of the cylinder. Power for the device is provided by a 3.7-V cordless-telephone battery. The valve is controlled by means of a pushbutton switch, which activates a 5-V to ±15-V DC-to-DC converter that powers the solenoid.

The outlet of the solenoid valve is connected to the pressure transducer to be tested. Before the solenoid is energized, the transducer to be tested is at atmospheric pressure. When the solenoid is actuated by the push button, pressurized air from inside the cylinder is applied to the transducer. Once the pushbutton is released, the cylinder pressure is removed from the transducer and the pressurized air applied to the transducer is vented, bringing the transducer back to atmospheric pressure. Before this device was used for actual calibration, its accuracy was checked with a NIST (National Institute of Standards and Technology) traceable calibrator and commercially calibrated pressure transducers.

This work was done by Wanda Solano of Stennis Space Center and Greg Richardson of Lockheed Martin Corp.

Inquiries concerning rights for the commercial use of this invention should be addressed to the Intellectual Property Manager, Stennis Space Center; (228) 688-1929. Refer to SSC- 00142.

NASA Tech Briefs Magazine

This article first appeared in the October, 2002 issue of NASA Tech Briefs Magazine.

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