GB1370103A - Process control apparatus - Google Patents

Abstract

1370103 Process control LUCAS ELECTRICAL CO Ltd 14 Jan 1972 [15 Oct 1971] 48024/71 Heading G4H Process control apparatus includes two transducers 21, 23 producing signals representing two parameters related to the process being controlled, a duration significant output control pulse being derived from the signals. As described each time a monostable 24 is triggered, gates 71, 72 are enabled for a predetermined time to feed frequency significant signals from transducers 22, 23 to counters 73 and 74 carrying over to counter 75 and 114. The counts in counters 75, 114 are decoded and used to enable one of the rows 11a-11p and one of the switches 15a-15b in a diode matrix arrangement 77 so that parallel coded signals representing the two parameters are fed to a comparator 53. At the start of the operation a bi-stable 46 is triggered which results in the output pulse being commenced and in a counter 52 being pulsed, after a delay determined by a counter 49, by pulses from a source 48 (which may be controlled in accordance with a third parameter). The counter output is fed as the outer input to the comparator 53, at equality of its inputs a counter 54 being incremented, counters 74, 75 and 72 reset and monostable 24 triggered. This process is repeated for a number of times determined by counter 54, the output from which, after, for example, 16 signals from the comparator, resets the bi-stable 46 to terminate the output pulse. Each pulse from comparator 53 also increments counters 86, 87 the counts in which consequently vary in a cyclic manner, the instantaneous count being entered into counters 73, 74 each time the monostable 24 is triggered. This is stated to compensate for small variations in the input. The delay introduced by the counter 49 ensures that a minimum output pulse length is always provided. Specifications 1,370,104 and 1,370,105 are referred to.