Abstract: A current sensing circuit has a transformer where a current to be measured induces a magnetic flux into a magnetic core. The magnetic core has a magneto-electric converter for sensing DC to low frequency current signals and a secondary winding for sensing higher frequency current signals. The magneto-electric converter generates an output that is coupled via an amplifier to a non-inverting input of a transimpedance amplifier. The inverting input of the transimpedance amplifier is coupled to the secondary winding of the transformer. A current signal path having a transimpedance resistor couples the inverting input to the output of the transimpedance amplifier. The transimpedance amplifier functions as a power amplifier for coupling a nulling current to the transformer for DC to low frequency current signals and functions as a transimpedance gain amplifier for higher frequency signals.

Abstract: A current probe transformer temperature monitoring method determines an initial transformer temperature of the current probe as a function of the winding resistance of the transformer. A relative temperature of the Hall Effect device is also determined as a function of resistance change of the Hall Effect device. The initial transformer temperature and the relative Hall Effect device temperature are combined to produce a continuous transformer temperature indicative of the temperature of the transformer. The current signal to the multi-turn winding is removed when the continuous transformer temperature exceeds a threshold temperature value and a visual indication may be provided.