Abstract: A flame sense circuit for a gas burner control employs a flame rod for flame rectification. An AC source applies an AC wave through a capacitor to the flame rod, and the flame rod is also connected via a resistive voltage divider to a DC voltage source. A voltage divider node is connected to a voltage follower, which impedance-matches an ADC input of a microprocessor controller. The flame sense circuit senses conditions of no-flame, and flame rod in contact with or leaking to ground, and when flame is present can quantify sensed flame as good, weak and marginal.