Abstract: The invention proposes a method for the flame signal detection by means of an ionization electrode (15) protruding into a combustion zone of a burner, comprising the steps: detecting a first signal, which is dependent on an ionization current flowing off the ionization electrode (15), generating a second signal which has a predetermined periodic course, generating a third signal by adding the first signal and the second signal, comparing the third signal with a first threshold value and generating a fourth signal on the basis of the comparison of the third signal with the first threshold value, comparing the third signal with a second threshold value different from the first threshold value and generating a fourth signal on the basis of the comparison of the third signal with the second threshold value, and determining an operating variable of the burner on the basis of at least one of the fourth signal and the fifth signal.

Abstract: The present invention relates to a method for controlling a heating unit comprising a burner (1) with a burner housing (2), an ionization electrode (7) associated with the burner (1), and a voltage supply (8) for applying an alternating voltage between the ionization electrode (7) and the burner housing (2), said method comprising the method steps: applying an alternating voltage between the ionization electrode (7) and the burner housing (2) by means of the voltage supply (8) and correcting the output of the voltage supply (8) in the event of parasitic leakage flows. The object of the present invention is in particular to improve the reliability when ascertaining the air-fuel ratio via the ionization current.

Abstract: The invention proposes a method for the flame signal detection by means of an ionization electrode (15) protruding into a combustion zone of a burner, comprising the steps: detecting a first signal, which is dependent on an ionization current flowing off the ionization electrode (15), generating a second signal which has a predetermined periodic course, generating a third signal by adding the first signal and the second signal, comparing the third signal with a first threshold value and generating a fourth signal on the basis of the comparison of the third signal with the first threshold value, comparing the third signal with a second threshold value different from the first threshold value and generating a fourth signal on the basis of the comparison of the third signal with the second threshold value, and determining an operating variable of the burner on the basis of at least one of the fourth signal and the fifth signal.