CAPACITIVE LEVEL SENSING DEVICE

摘要

A capacitance sensing circuit utilizes an operational amplifier connected in a comparator configuration. The capacitance to be measured is connected to one input of the operational amplifier and is also connected to the output of the operational amplifier through a resistor to form a free-running multivibrator. The period of the multivibrator output depends upon the value of capacitance being measured. A switching transistor is connected to the output of the operational amplifier to cause a changing current output signal. The output signal is obtained as a change of current in a current sensor connected to the collector of the transistor.