Hysteresis compensated reed switch assembly for a position indicating system

摘要

The position of a control rod located within a nuclear reactor is sensed by a position indicating system utilizing low hysteresis reed switch assemblies. Each reed switch assembly includes a reed switch having an alternating magnetic flux field applied thereto through a coil surrounding the reed switch and energized by an alternating current power source. The amplitude of the alternating magnetic flux field is adjusted to be between a first flux level required to close the reed switch and a second flux level required to open the reed switch. The level of the alternating magnetic flux field is preset to be below the second flux level to maintain the switch in the open position until an external flux field is introduced to raise the total flux level above the first flux level to actuate the reed switch to close. The interaction of the alternating and external flux fields negates the hysteresis band of ordinary reed switches and provides a more sensitive and accurate position indicating circuit.