Abstract: A flame detector and burner fuel valve control has an ultraviolet sensitive, cold cathode, gas discharge tube in a DC quench circuit. In the presence of a flame, the circuit generates a pulse signal at a frequency related to the intensity of radiation from the flame. The pulse signal from a contaminated tube is at a higher frequency. A frequency discriminator circuit distinguishes between a flame responsive signal and a contaminated tube signal and controls the burner fuel valve.

Abstract: A flame detector and burner fuel valve control has an ultraviolet sensitive, cold cathode, gas discharge tube in a DC quench circuit. In the presence of a flame, the circuit generates a pulse signal at a frequency related to the intensity of radiation from the flame. The pulse signal from a contaminated tube is at a higher frequency. A frequency discriminator circuit distinguishes between a flame responsive signal and a contaminated tube signal and controls the burner fuel valve.

Abstract: A multi-stage, fail-safe fuel control circuit monitors a flame which emits photons and is supplied with fuel through a valve to a burner. The fuel control circuit includes a flame scanner adjacent the valve for generating a count signal including pulses provided at a rate proportional to the energy of the flame adjacent the burner. A timer provides at least one timing signal which periodically shifts between a first and second state. A capacitive pulse-height discriminator is coupled to the flame scanner and to the timer and measures the rate of the pulses in the count signal during the first state of the timing signal and generates a discriminator signal if the pulses exceed a desired rate during the first state. A capacitor discharge oscillator is coupled to the frequency discriminator and the timer charges a capacitor during the first state and provides an oscillating signal powered by the capacitor at a first frequency if the count discriminator signal is generated during the first state.