A capacitor connected to a voltage source is charged during a charging phase up to a voltage value, and during a discharging phase the capacitor is discharged via a coupling element connected to the flame sensor. The period for the charging or discharging phase of the capacitor respectively is selected...http://www.google.es/patents/US7382140?utm_source=gb-gplus-sharePatente US7382140 - Method and device for flame monitoring
