초록 ▼

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 mu

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.

대표청구항 ▼

A capacitance sensing circuit comprising: a voltage comparator with two inputs and an output, said output having either a high or a low state depending on the relative value of signals at said inputs; a reference signal source connected with one of said inputs; an unknown capacitor connected with th

A capacitance sensing circuit comprising: a voltage comparator with two inputs and an output, said output having either a high or a low state depending on the relative value of signals at said inputs; a reference signal source connected with one of said inputs; an unknown capacitor connected with the other of said inputs; a resistor connected between said output and said other input, said capacitor charging and discharging through said resistor to develop a signal which causes said comparator output to change state and develop an output signal having a period which depends on the capacitance of said unknown capacitor; a transistor having a collector connected to the output of said comparator; and a current sensor connected to said collector so that a signal having the same period as the output signal is developed across said current sensor.