Patent Number: 6,529,017

Title: Capacitance level measurement circuit and system

Abstract: A capacitance measurement circuit and probe includes a drive circuit couplable to a constant-current source, a threshold detector, a probe capacitor, and a reference capacitor. The circuit includes a plurality of switches being actuatable to alternately couple the current source to the probe capacitor and to the reference capacitor. The drive circuit is configured to alternately generate a signal of linear ramp waveform having a slope that is proportional to the magnitude of capacitance of the probe capacitor and of the reference capacitor. The voltage differential between the probe capacitor and reference capacitor are actively nulled to nominally eliminate a parasitic capacitance therebetween.

Inventors: Martin; Barry E. (Cleveland, TN), Tymoszuk; Stephen (Knoxville, TN), Lease; Benjamin N. (Knoxville, TN)

Assignee: RobertShaw Controls Company

International Classification: G01F 23/26 (20060101); G01F 23/22 (20060101); G01R 027/26 (); G01F 023/00 ()

Expiration Date: 03/04/2020