GB1187541A - Automatic Monitoring System - Google Patents

Abstract

1,187,541. Sampling radiation. ATELIERS DE MONTAGE ELECTRIQUES. Jan.22, 1968 [Jan.20, 1967], No.3226/68. Heading G1A. In a sampling system both the duration of individual sampling operations and the interval between samplings are discretely altered as the level of successive samples transgresses a threshold value. An apparatus for measuring radioactive particle content of air by deposition on a filter paper is described. As shown a pump 13 is periodically operated say for four minutes once every hour and draws air through a portion 14a of the filter paper. After each period the paper is advanced by a motor 16 so that the exposed portion moves to a detecting zone 14b adjacent a Geiger counter 17. The pulses produced by the Geiger counter are amplified at 19 and after regneration by a monostable circuit 20 are applied to a gate 21 which is opened at the appropriate time for a period determined by a timer 41. The pulses passed by the gate are applied to a divider circuit 22 which passes every pulse, every other pulse or every fourth pulse (according to its setting as described below) to a counter 24 and to a printer 23. The counter 24, a threshold valve storage circuit 27 and a comparator 28 together constitute a counter which gives an output pulse on a line S 1 when the count passes a first threshold, an output pulse on a line S 2 when the count passes a second threshold and an output on a line a to an alarm device 29 when the count passes an alarm threshold. The pulses on the lines S 1 and S 2 are counted on a counter (not shown) within a circuit 25. The counter which comprises a pair of bistables is re-set once during each period and controls latching relays which determine the scaling factor to be used by the divider 22 during the next test period. The relays also control a speed reducer 262 through which a cam shaft 263, functioning to produce timing signals for the various operations, is driven. Thus for example as the level of radioactivity detected increases the sampling periods change from four minutes once every hour to two minutes once every half hour then to one minute every quarter hour. The precise moment at which a danger level is reached can thus be determined accurately while economising on power that may be supplied from a battery.