A Method for Compensation of Thermal Drift of Ferromagnetic Current Comparator

The current comparator using a ferromagnetic core has several merits especially for application to current A-D converters. Because the comparator utilizes the coercive force of the core to give the threshold value to the performance, drift errors cannot be neglected if the ambient temperature changes. An electronic compensation method for drift and experimental results are described. The temperature drift in the performance of the comparator is decreased from 120 mA to 1 mA over the temperature range of 10°C to 55°C. The thermal drift of the compensated comparator is less than that of the comparator at constant temperature. Using the compensation method, accuracy of the current A-D converter with the comparator is maintained to an order of 0.1 percent of the maximum value of the input over wide temperature range.