Opto-electric approach sensor has light emitting sender and a receiver

摘要

Opto-electronic approach sensor (7,9) has a control circuit (3), a sensor assembly (2a) and a receiver assembly (2b). Typically the sender is an LED (7) which controls a receiver (10), which is part of the receiver assembly. The control circuit (3) tells the LED (7) to emit a coded, amplitude modulaed alternating light signal (8), this is received by the receiver (10), which then passes the signal to a narrow band linear amplifier with a switching circuit or signal changer (12,13) to demodulate the signal. Depending on the sensitivity of the receiver and the strength of the amplification the signal will be strong enough (depending on approach distance) to cause the switching circuit to operate.