GB1346711A - Arrangements for monitoring ionising radiation - Google Patents

Abstract

1346711 Monitoring ionizing radiation INTERNATIONAL STANDARD ELECTRIC CORP 29 Feb 1972 [1 March 1971] 9238/72 Heading G1A In a supervisory circuit monitoring a measuring device which comprises a measuring channel(s) 1, 2 including an ionizing radiation source(s) 5, 6 and a detector(s) 8, 9, a reference source of radiation 7 and a detector 10 are selected such that the dose rate of reference source 7 should be less than (or greater than) the dose rate(s) due to radiation source(s) 5, 6, and the count rate from each detector 8, 9 and 10 of each channel is converted to an analogue electrical signal in corresponding converters 15, 16, 17, the analogue electric signals due to source(s) 5, 6 being compared in a comparator 21 with the analogue signal due to the reference source 7, wherein the comparator operates an alarm 22 when the measuring signal(s) are smaller than (or greater than) the reference signal. The converter circuit may comprise a buffer amplifier, an integrating element, and an analogue amplifier (Fig.3, not shown). The comparator circuit may comprise two differential amplifiers for measuring channels 1 and 2 each amplifier also receiving the reference signal, the outputs from the differential amplifiers being fed to a comparator including a reference voltage or current which sets a threshold for an output by the comparator and the reference source is chosen so that one measuring signal is usually greater than the reference signal and one is usually less. In a further similar embodiment, Fig.4, the converter circuits 15, 16 and 17 each comprise a gate 40, a digital counter 41 and a digital-toanalogue converter 42. When a digital counting circuit reaches a predetermined count (erase count) the digital counting circuit produces on a reset line 44 a pulse which via an OR circuit 45 resets the digital counting circuit 41 to zero and during this operation blocks via a further OR circuit 46 the gate circuit 40 to counting pulses. As shown the reset line 44 of each converter arrangement is connected to the reset inputs of all other converter arrangements. The outputs are connected to differential amplifiers 36, 37 as shown whose outputs pass via an OR circuit to an alarm or recording device 22.