High frequency sensor with contactless switching and measuring

摘要

The sensor consists of an IC-4093, a control resistance (R8), a transistor (T1), a polarity changeover diode (D1) and a 1.5 cm long antenna wire (A1). The circuit is connected as an oscillator using a 27 kOhm resistance (R1). The oscillator transmits its power at a pin (11) of the IC 4093 and changes its output voltage when a capacitance approaches so as to cause a switching or measurement process. The applied voltage at the circuit and the control resistance result in a voltage state which varies in proportion to the capacitive variation, whilst circuit stability is maintained by a transistor circuit (R4,R5,T1), enabling the voltage to be used for switching or measurement without noise effects.