Measurand transient signal suppressor

Abstract

A transient signal suppressor (10) for use in a controls system which is adapted to respond to a change in a physical parameter whenever it crosses a predetermined threshold value in a selected direction of increasing or decreasing values with respect to the threshold value and is sustained for a selected discrete time interval. The suppressor (10) includes a sensor transducer (12) for sensing the physical parameter and generating an electrical input signal whenever the sensed physical parameter crosses the threshold level in the selected direction. A manually operated switch (30A, 30B) is provided for adapting the suppressor to produce an output drive signal whenever the physical parameter crosses the threshold value in the selected direction of increasing or decreasing values. A time delay circuit (40,42) is selectively adjustable for suppressing the transducer input signal for a preselected one of a plurality of available discrete suppression time and producing an output signal only if the input signal is sustained for a time greater than the selected suppression time. An electronic gate (25) is coupled to receive the transducer input signal and the timer output signal and produce an output drive signal for energizing a control relay (33) when transducer input is a non-transient signal which is sustained beyond the selected time interval.