Pulse operated digital evaluation network - is for frequency modulated monitoring applications such as flame monitoring diode based devices

摘要

The digital evaluation network has three parts, the first (A) of which consists of a frequency checking counter arrangement which uses the incoming pulses to increment a counter (B) over a fixed time interval (T1). If at the end of this time interval a threshold number (N) has been achieved then a lamp is illuminated by means of a signal (F) of a fixed time (T2) duration, and the cycle is restarted. If the threshold number is not achieved, then no input signal is produced and the cycle is in any case restarted. This output signal (F) is produced by the second section. The third section concerns a check on the operational state which relies on closing the flame observation aperture and noting that no impulse count is recorded in the frequency checking section.