Circuit for monitoring an electric circuit for conductor breaks particularly for input and output circuits of sensors

摘要

The circuit monitors the voltage drop across a resistor in the sensor supply or the sensor output lead. To monitor the input circuit, a voltage divider (20) with two resistors (22,24) is located in the supply lead (32) to the sensor. The center point (42) between the resistors is connected through a filter (16) to two threshold detectors. One detector (44) is set to operate below a threshold that represents a specific minimum current indicating a conductor break. A second detector (52) monitors the logic state of the input signal to the detectors indicated by LEDs (48,56). To monitor the output circuit, a single detector monitors the voltage across a diode connected between the output lead and ground.