초록 ▼

A proximity sensor of the electrostatic type has a pulse-generating circuit and first and second delay circuits which are respectively connected to an output of the pulse-generating circuit. The first and second delay circuits are of the integrating type having capacitances which are charged over ti

A proximity sensor of the electrostatic type has a pulse-generating circuit and first and second delay circuits which are respectively connected to an output of the pulse-generating circuit. The first and second delay circuits are of the integrating type having capacitances which are charged over time. The second delay circuit is a reference circuit and has a delay based on a fixed capacitance. The first delay circuit has its capacitance based on a capacitance of a detection electrode. The first and second delay circuits each have their respective capacitances charged or drained by constant current circuits, each moving the same amount of current. Outputs of the first and second delay circuits are each applied to a respective limiting amplifier such as a Schmitt trigger, each Schmitt trigger then has an output to input to a common phase detector. The phase detector determines the sequence of arrival of pulses generated by the first and second delay circuits. Since the constant current sources charge their respective capacitances in a linear fashion, arrival of noise spikes anytime during the charging period results in consistent errors which are less than errors associated with a noise spike of the same level in the prior art.

대표청구항 ▼

A proximity detector comprising: a pulse generator; first and second delay circuits receiving an output of said pulse generator and having first and second capacitances respectively; an electrostatic capacitance varying converter connected to at least one of said first and second delay circuits to v

A proximity detector comprising: a pulse generator; first and second delay circuits receiving an output of said pulse generator and having first and second capacitances respectively; an electrostatic capacitance varying converter connected to at least one of said first and second delay circuits to vary a delay of said at least one delay circuit by varying a respective one of said first and second capacitances; said first and second delay circuit each having a constant current circuit, controlled by said pulse generator, for changing a set state of charge on said first and second capacitances, respectively, in a substantially linear manner; and a phase discrimination circuit for detecting a phase difference between outputs of said first and second delay circuits.