Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Patent
1992-06-22
1995-01-03
Williams, Hezron E.
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
7386142, 7386147, G01F 138
Patent
active
053775244
ABSTRACT:
A high-performance switched-capacitor circuit for electronic read-out of a pressure sensor-based ultrasensitive microflow transducer. The microflow transducer uses a differential capacitive pressure sensor to measure flow. Read-out electronics associated with the transducer feature a clocking speed of 100 KHz and drive loads up to 35 pF. The read-out electronics include a high DC gain that nulls out stray input capacitance, which is beneficial for the multichip realization of the microflow transducer disclosed herein. The uncompensated linearity of the overall read-out electronics is 10 bits, and the pressure/flow resolution is 12 bits. An ultrasensitive membrane associated with the pressure sensor does not respond to a pulsed waveform for frequencies above 50 KHz. But for lower frequencies, it deflects in response to the time-average voltage applied across the capacitor plates of the pressure sensor. A self-test mode is provided which employs an extremely long pre-charge pulse. An integrated flowmeter package including transducer and circuitry, and a second circuit for extending the range of the microflowmeter circuitry are also disclosed.
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Cho Steve T.
Wise Kensall D.
Dombroske George M.
The Regents of the University of Michigan
Williams Hezron E.
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