Flow rate and low flow indicator

Claim 1

In a system for indicating flow rate and signalling flow below a predetermined minimum, the combination of: A means for generating electrical pulses at a frequency proportional to flow rate, A first circuit means for indicating flow rate, A second circuit means for signaling flow rate below a predetermined minimum, A said second circuit including a first transistor connected at its base to said pulse generating means to receive said pulses and a capacitor connected across the collector and emitter of said first transistor, an AC source, a first diode and a variable resistor connected in series to said AC source for providing a variable DC current from said AC source and a gas diode and a relay connected to series with said variable resistor, said capacitor being further connected to said series between said variable resistor and said gas diode whereby under normal flow said capacitor is charged by said DC current and periodically discharged when said first transistor receives a pulse from said pulse source thereby becoming conductive but under flow less than said predetermined minimum when said pulses are less frequent, said capacitoR will over charge thereby ionizing said gas diode, permitting said relay to switch, And a signalling means actuated upon said switching of said relay to give a signal of flow less than said predetermined minimum.