Patent ID: 7589538

Claim:
A voltage independent method of measuring an at least one unknown capacitance, which comprises the steps of: generating a first time varying signal using a voltage independent oscillator circuit comprising a single integrated circuit analog timing device, the first time varying signal having a period which is linearly proportional to the at least one unknown capacitance; counting a number of cycles of the first time varying signal occurring within a first predetermined time period and providing a counted number of cycles of the first time varying signal; determining the period of the first time varying signal from the counted number of cycles of the first time varying signal; generating a second time varying signal using the same voltage independent oscillator circuit as is used to generate the first time varying signal, the second time varying signal having a period which is linearly proportional to a known reference capacitance; counting a number of cycles of the second time varying signal occurring within a second predetermined time period and providing a counted number of cycles of the second time varying signal; determining the period of the second time varying signal from the counted number of cycles of the second time varying signal; comparing the period of the first time varying signal with the period of the second time varying signal; and determining the value of the at least one unknown capacitance from the comparison of the periods of the first time varying signal and the second time varying signal.