<p>The burner system has a grounded burner (1), actuators, flame amplifier including an ionization electrode for producing ionization signal, and control device for controlling air-fuel ratio. An alternating current (AC) voltage source (14) generates AC voltage for electrode. A voltage regulator (19) controls the AC source using measured AC voltage and reference voltage. The voltage control operation of voltage meter (20) is performed such that the time-averaged current flowing through voltage meter is greater than 5% of the time-averaged current flowing through electrode.</p>
