Patent ID: 8773137

Claim:
A method for flame sensing in a solid, liquid or gaseous fuel burner, comprising the steps of: generating said flame at an ionization electrode, presence of the flame resulting in an ionising effect on said ionization electrode to generate in this ionization electrode a direct current, said direct current being sensed by a sensing circuit comprising a control unit, said control unit connected to a flame current sensing circuit for sensing a flame current, the flame current corresponding to the state of the flame, generating, directed towards the ionization electrode, an alternating voltage signal of waveform, amplitude and duty cycle to reduce to a value less than 1 the ratio of the direct current flowing through the electrode to measured flame current, wherein said alternating voltage signal is generated by a generator of relatively low impedance, between 50 KOhm and 5 MOhm, the control unit measuring the value of the negative current due to parasitic elements, this control unit subtracting that value of the negative current due to parasitic elements from the current value or positive current measured in the positive part of the feed voltage, originating from the electrode and generated both by electrode ionization due to flame and by the parasitic element, this enabling a value to be identified for the current effectively generated by just the flame on the electrode.