GB1293505A - Temperature sensing apparatus - Google Patents

Abstract

1293505 Measuring electrical energy CGR MEDICAL CORP 19 April 1971 [15 April 1970] 24945/71 Heading G1U [Also in Division H2] Apparatus for monitoring the temperature of a load supplied with electrical energy comprises a generator 30 providing pulses whose frequency is proportional to the load current, a modulator 40 which regulates the amplitude of the pulses in accordance with the load voltage, an integrator 50 for integrating the modulated pulses, and a discharge path, e.g. R, which allows the integrator output to decay at a rate corresponding to the cooling rate of the load. Two discharge paths may be included, one providing for an exponential voltage decay and comprising a resistor R across the integrator capacitor 51, and the other, said to provide a linear decay, comprising a resistor between the input side of capacitor 51 and the h.t. supply. The integrator output is indicated directly on a meter 90 and is also applied to a Schmitt trigger 70 to energize a circuit breaker 95 and a triac 80 driving an alarm indicator 88 when the integrator output, and hence load temperature, become too large. The load may be the anode of an X-ray tube, a signal proportional to the anode current being derived by a shunt 5 supplied via a bridge rectifier (4A, Fig. 1, not shown) in the secondary circuit of the X-ray tube. supply transformer (3). A diode (54) across the integrator capacitor 51 prevents spurious voltages building up when the X-ray tube is initially energized.