Hot spot anomaly detector for electrical circuit - uses differential amplifier coupled to two points in circuit and threshold detector to activate alarm if circuit resistance rises

摘要

The device detects anomalies in the conduction in an electric circuit, e.g. containing a motor, particularly high resistance zones which may result in fire. A differential amplifier has its inputs connected to two points in the test circuit. Voltage limiting circuits protect the differential amplifier from overvoltages. The voltage drop between the two points in the electric circuit sets up an output from the differential amplifier, which is coupled to a threshold detector. If the circuit volt drop causes the detector threshold to be exceeded, then the threshold detector gives an output signal which drives a power amplifier driving a relay with its contacts connected in an alarm or telemetry circuit. The inputs of the differential amplifier are protected by zener diodes.