Non-contact capacitive sensor for scanning of labels on carrier - processes frequency-modulated signal by demodulator with post-controlled carrier reference frequency, amplifier, low=pass filter, and voltage-controlled filter which outputs both to trigger, and to peak detector in feedback circuit

摘要

A frequency modulated signal from an oscillator (12) is led to an electronic signal processing circuit (3), across a sensor connection line (2). This circuit consists of a demodulator (31), a voltage controlled amplifier (32), a low-pass filter (33), a voltage-controlled filter (34), and a peak value rectifier (35). A sample-and-hold circuit (36) receives the output from the peak rectifier and outputs to storage. A voltage controlled trigger (37) with a voltage controlled threshold value adjustment is also coupled to the voltage-controlled filter (34) for converting the analog signal at the filter output to a binary signal, indicating the presence of a label. The sensor system can be matched to different types of labels, by the post-control of the carrier reference frequency in the demodulator (31) and the change-over of the sample-and-hold circuit (36) from a working mode to a learning mode. USE/ADVANTAGE - Esp. suitable for monitoring of greatly-varying labels mfd. on carrier strip. Correct placing is achieved with differing material pairs and label geometry. Monitoring can be carried out at high speed.