A method for detecting a flame is provided. The method includes the step of providing alternating current to a flame rectification probe to produce a first voltage as an input for a sense circuit, wherein the flame rectification probe is placed in proximity to the flame. The method further includes the step of conditioning the first voltage using the sense circuit to produce a second voltage. Additionally, the method includes the steps of outputting the second voltage to a microcontroller, and determining with the microcontroller whether the flame is present based on a magnitude of the second voltage.

A means of detecting the in-situ fuel-to-air-ratio (FAR) in a combustor or flame zone using a Fourier-based flame ionization probe is presented. The use of multiple excitation frequencies and its detection at certain frequencies or combinations of harmonics of those excitation frequencies, namely, the inter-modulation distortion, provides a novel means of extracting a high signal-to-noise ratio (SNR) FAR measurement in a combustor.

A system for igniting a grill can include a solenoid valve, a flame rectification sensor, an igniter, and a control circuit connected to the solenoid valve and the flame rectification sensor. The solenoid valve controls flow of gas to the grill's burner and includes a switch that closes when a handle connected to the switch opens the solenoid valve. The control circuit sends current to the solenoid valve when the switch is closed to hold the solenoid valve open. After the switch closes, the igniter is ignited. After ignition, the control circuit monitors the presence of a flame with a flame rectification sensor. If no flame is detected after a certain amount of time, the control circuit stops sending current to the solenoid valve to close the solenoid valve.

A cooking appliance is disclosed that according to one embodiment includes a plurality of gas burners, an electrode associated with each burner for igniting the flame, a flame sensor associated with each burner for monitoring the flame and at least one electric switch associated with an actuator that is transitional between open and closed positions. The cooking appliance also includes a control unit electrically connected to the electrodes, the flame sensors, and the switch. When the switch assumes the closed position, the control unit is activated and then in turn powers the electrodes and the flame sensors. Thereafter, the control unit sequentially monitors the presence or absence of flame in the burners during repeated time cycles.

A method for controlling operation of a fuel-fired heating appliance having a burner, a fuel flow control for controlling a fuel flow to the burner, and a combustion air blower for supplying combustion air to the burner, includes iteratively (1) determining the quality of combustion by sensing a flame at the burner and outputting a time-varying flame current signal that includes an ionization signal from the flame; sampling the flame current signal to obtain a time record of the flame current signal; using a Fourier transformation, transforming the time record into a frequency spectrum of frequency components that include frequency components of the ionization signal, the frequency spectrum having a spectrum shaped defined by various frequency components of the flame current signal; and determining whether the frequency spectrum indicates flame stability or instability. Upon determination of flame instability, adjusting at least one of the fuel flow control to decrease the fuel flow to the burner and the combustion air blower to increase the flow of combustion air to the burner, and shutting down the burner if flame stability is not determined within a predetermined interval.

A means of detecting the in-situ fuel-to-air-ratio (FAR) in a combustor or flame zone using a Fourier-based flame ionization probe is presented. The use of multiple excitation frequencies and its detection at certain frequencies or combinations of harmonics of those excitation frequencies, namely, the inter-modulation distortion, provides a novel means of extracting a high signal-to-noise ratio (SNR) FAR measurement in a combustor.

A flame scanner (10) includes terminals (32) for connection to a controller (50) The flame scanner includes a photodiode (14) to generate a detection signal; and a signal conditioner (20) coupled to the photodiode, the signal conditioner to generate an output signal across the terminals, the output signal emulating an output of an ultraviolet tube flame scanner.

A gas burner system has a gas burner with a conduit through which an air-gas mixture is conducted; a variable-speed forced-air device that forces air through the conduit; a control valve that controls a supply of gas for mixture with the air to thereby form the air-gas mixture; and an electrode configured to ignite the air-gas mixture so as to produce a flame. The electrode is further configured to measure a flame ionization current associated with the flame. A controller is configured to actively control the variable-speed forced-air device based on the flame ionization current measured by the electrode so as to automatically avoid a flame harmonic mode of the gas burner. Corresponding methods are provided.

A flame rod analysis system, methods for determining a condition of a flame and a flame rod, and circuits for determining a condition of a flame and a flame rod. The flame rod analysis system comprises energy storage connectable to a flame rod, a pulsed source connected to the energy storage and providing a voltage pulse or a current pulse, and a buffer to allow a processor to measure a buffered voltage at various time points. Flame rod analysis systems can distinguish between various flame conditions (no flame, low flame, etc.) while simultaneously characterizing the condition of the flame rod (shorted to ground, contaminated, etc.). Some flame rod analysis systems can directly measure the resistance of the flame rod.

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.