Capacitor measuring circuit compensating for lead capacitance errors - uses integrating operational amplifier with capacitor in feedback path and AC voltage input

摘要

A circuit having a capacitor (1) in the feedback path of an operational amplifier (2) which has an ohmic impedance (3) connected to its inverting input is applicable to analogue computation as an inverting integrator. The circuit is developed for use as a simple effective capacitance measurement circuit. The feedback capacitor (1) is a measurement capacitor. An a.c. voltage is applied to the amplifier (2) inverting input via the ohmic impedance (3) and a measurement instrument (22) is connected to the output of the amplifier. The capacitance measurement takes place practically independently of the connector capacitance magnitudes and variations. The arrangement enables dynamic capacitance variations to be measured. The earthing capacitance effect is negligible if an operational amplifier closely approximating the ideal is used. Connector capacitance compensation circuits can be incorporated.