| US 7,516,669 B2 | ||
| Capacitance sensing circuit for a pressure sensor | ||
| Kia Silverbrook, Balmain (Australia); and Samuel George Mallinson, Balmain (Australia) | ||
| Assigned to Silverbrook Research Pty Ltd, Balmain, New South Wales (Australia) | ||
| Filed on Jan. 16, 2008, as Appl. No. 12/15,390. | ||
| Application 12/015390 is a continuation of application No. 11/642520, filed on Dec. 21, 2006, granted, now 7,334,480. | ||
| Application 11/642520 is a continuation of application No. 11/446238, filed on Jun. 05, 2006, granted, now 7,171,855. | ||
| Application 11/446238 is a continuation of application No. 10/965902, filed on Oct. 18, 2004, granted, now 7,089,797. | ||
| Prior Publication US 2008/0110270 A1, May 15, 2008 | ||
| Int. Cl. G01L 9/12 (2006.01) | ||
| U.S. Cl. 73—724 [73/715; 73/718; 73/723; 361/283.1] | 8 Claims |
| 1. A capacitance sensing circuit for a pressure sensor having a sensor membrane and a compensation membrane, the circuit comprising
a controller; and
a charge amplifier, a charge injector and two switches, in signal communication with the controller, the charge amplifier
connected to the switches via a sensor capacitor Cs in parallel with a reference capacitor Cr in parallel with a parasitic capacitance Cp to ground, the charge injector and charge amplifier arranged in parallel connection between the capacitors and controller,
the controller configured to determine a charge imbalance indicative of a pressure difference between the sensor and compensation
membranes.
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