Abstract: A water heating system includes a burner and a gas valve fluidly connected to the burner to deliver a flow of combustible gas thereto. The gas valve has an adjustable throttle for the flow of combustible gas, along with a motor to adjust a position of the throttle. A controller is configured to determine a throttle position corresponding to a target air-fuel ratio of the burner during a calibration sequence, and to control the motor in order to operate the burner at that target air-fuel ratio throttle position during a start sequence. The controller is configured to monitor a characteristic of the burner during the start sequence, and to initiate the calibration sequence if the monitored characteristic exceeds an error threshold.

Abstract: A gas powered appliance includes a burner for burning gas, a flame sensor positioned proximate the burner to detect a strength of a flame on the burner and to output signals indicative of the strength of the flame, and a controller connected to the flame sensor. The controller includes a communication interface, a processor, and a memory containing instructions that program the controller to control the burner, receive the signals from the flame sensor indicative of the strength of the flame, determine the strength of the flame from the received signals, and output, using the communication interface, an indication of the strength of the flame to a mobile device for display on the mobile device.

Abstract: A method and system for advanced flare analytics in a flare operation monitoring and control system is disclosed that contains a data acquisition and augmentation mechanism whereby data is aquired through a plant network including images of the flare operations from single or multi-camera hubs. A machine learning-based self-adaptive industrial automation system process the images and data and assigns pixels to the images according to categories selected from smoke, flame and steam. The results of the analysis are displayed and a notice is issued when the percentage of pixles in a specific category falls outside a predeterminmed range.

Abstract: A control system of a water heater apparatus with a combustible gas burner is presented where the apparatus includes a pilot burner with an intermittent-type pilot flame, a main burner, a pilot valve and a main valve, a control unit, a flame detection electrode, introduced into the flame of the pilot burner, and which is configured to conduct an ionization current. The control unit is configured to measure/detect a variation involving increase/decrease of the intensity of ionization current detected, the variation in intensity of ionization current being generated during the change between a first condition, in which the ionization current identifies the ignition state of only the pilot burner, and a second condition, in which the ionization current identifies the simultaneous ignition state of the pilot burner and the main burner so that, by detection of the measurement/variation of ionization current, the effective ignition of the main burner is recognized.

Abstract: Operating a gaseous fuel engine system includes determining a detonation level in combustion cylinders in an engine in the gaseous fuel engine system, comparing the detonation level to a detonation level limit, calculating a detonation error, and limiting an engine load of the engine to a derated engine load level based on a reduction to intake manifold air pressure (IMAP) that is performed responsive to the detonation error. The gaseous fuel engine system can be operated at a reduced, derated engine load, rather than being shut down, and permitted to increase in engine load level as detonation events clear. Related control logic and structure are disclosed.

Abstract: System and method for measuring flame temperature profile are disclosed. The temperature measurement system disclosed measures temperature profile of coal burner flames in a multi-burner furnace environment by capturing temperature images using optical devices. Any point or area of temperature captured in the image is determined by the ratio of the magnitude of the near infrared (NIR) light and the visible red light of that particular point or area, from which the temperature distribution of burner flame is developed. The two light ratio method can minimize the impact on the flame temperature measurement caused by the flame soot in a furnace and thus can greatly improve the temperature measurement accuracy.

Abstract: A smoke alarm comprises smoke detection circuitry for detecting smoke and generating a detection signal responsive thereto. Proximity detection circuitry generates a proximity detection signal responsive to detection of an object within in a selected distance of the smoke alarm. Alarm generation circuitry generates an audible alarm responsive to the detection signal. The audible alarm may be deactivated for a predetermined period of time responsive to at least one proximity detection signal.

Abstract: A method for flame sensing in a solid, liquid or gaseous fuel burner, the flame generated at an ionization electrode, the flame presence resulting in an ionizing effect on the electrode. The electrode is powered by an alternating voltage signal. The ionization phenomenon generates in the electrode a direct current. The current being sensed by a suitable sensing circuit including a control unit. This signal generator being of relatively low internal impedance to enable the measured generated current to have a high value compared with that normally used and of waveform to tend to limit the value of the direct current flowing through the electrode. The sensing and control circuit being such as to enable the presence of a parasitic current on the flame sensing electrode to be measured. A device for implementing the method is also disclosed.

Abstract: A fire alarm consists of a housing in which sensors, a radiation source, and an optical window are disposed. A reflector protection basket or ring is disposed above the optical window. The basket or ring is suitable for protecting the optical window against mechanical influences, allows UV and IR radiation to pass through to a sufficient degree, and reflects UV and IR radiation from the housing interior, on its inside. Monitoring of the contamination of the window, function monitoring of the sensors and of the signal processing electronics, as well as easy replaceability of the components in the fire alarm are provided.

Abstract: Systems and methods for indicating the unsafe service handling temperature of an information handling system component are disclosed. A method may include sensing a surface temperature of the component and comparing the surface temperature to a first and second threshold temperatures. The method may further include displaying various temperature warning by multiple temperature indicators if the surface temperature is above or below the threshold temperatures.

Abstract: A smoke detector comprises a soft x-ray source (10) and an air space (16) communicating with ambient air (18) and positioned so that soft x-rays produced by the soft x-ray source (10) pass into the air space (16) to ionise air in the air space (16). A detector (14) is positioned for detecting ionised air in the air space (16). Smoke particles entering into the air space (16) mop up ionised air. This leads to a reduction in the number of ions detected which triggers an alarm. The soft x-ray source (10) preferably comprises a substrate (22) on which are provided a plurality of nanometer scale elongate structures (28). The elongate structures (28) are provided in an evacuated chamber (42) formed between the substrate (22), a spacer (30), and a laminated film (36). The laminated film (36) comprises an aluminum foil layer (38) and a supporting nylon layer (40). A voltage converting circuit (44) is powered by a 9 volt DC battery and applies a 1.

Abstract: A fire detection switch for use in a fire detection circuit of a aircraft engine, having: a first resistor and a second resistor disposed in series between a common terminal and an alarm terminal; and a thermally-sensitive element having a different resistance at low temperature than at high temperature, the thermally-sensitive element disposed in series with the second resistor and in parallel with the first resistor.

Abstract: The flame ionization detector, which comprises a supply and an ignition device (7) for the combustible gas, a supply for the sample gas, a combustion chamber (4) in which the sample gas is ionized by the flame, and electrodes (8, 1) to which a voltage is applied in order to generate and measure the ion current, is distinguished in that it is constructed as an integrated planar system of at least three parallel platelet-like substrates (1, 2, 3) which are connected to one another and are processed by microsystem technology methods, with a central substrate (1) comprising nozzles (5, 6) for the gases and the ignition device (7) and a recess which forms a part of the combustion chamber (4), is completed by recesses in the neighboring substrates (2, 3) and is essentially closed together with the nozzle region by these substrates (2, 3), and the neighboring substrates (2, 3) comprise supply channels (10, 11) for the gases.

Abstract: A method for automatically detecting a control signal configuration of a vehicle component includes making a connection to a channel of the component, performing an electrical measurement on the channel, and identifying a control signal configuration based upon the measurement. A method for sending control signals from one vehicle component to another includes making a connection on a channel of one component, making a connection to a channel of the other component, performing electrical measurements on the channels, identifying control signal configurations based upon the measurements, and configuring a control signal interface. A control signal interface includes an input unit, a signal processing unit, and an output unit. The input and output units each can connect to a channel of a vehicle component and perform an electrical measurement. The signal processing unit can determine control commands based upon control signals.

Abstract: A fire detector and method of using it generate a fire alarm through use of a smoke detector and a carbon monoxide detector once the smoke detector detects a threshold level of light obscuration for greater than a first pre-selected time period or a reduced threshold level of light obscuration for greater than a second pre-selected time period or the CO detector detects a rate of increase in CO concentration which exceeds a first preselected CO rate for a third pre-selected time period and the smoke detector detects the reduced threshold level of light obscuration or the rate of increase in CO concentration exceeds a second preselected CO rate for a fourth pre-selected time period.

Abstract: An aftermarket steering wheel control includes a housing that includes a user-operable switch and a control module. The control module is configured to determine whether the user-operable switch has been operated, generate a data frame corresponding to a control signal for operating a vehicle component, and transmit the data frame to a receiver of a control signal interface. Another aftermarket steering wheel control includes a housing with a user-operable switch and a circuit with an output line. The output line is connected to the switch and further connected to a control signal interface. Operation of the user-operable switch changes a resistance on the at least one output line, and the control signal interface is configured to convert the resistance to a control signal for operating a vehicle component.

Abstract: A collection and detection system is directed to a combined system in which a detect to warn system is integrated with a detect to treat system. Such a combined system provides multi-levels of detection to determine the presence and identity of one or more different types of specific particles. In some applications, the combined system is configured to detect and identify one or more different types of specific biological particles such as toxins and pathogens. The combined system includes a first level detection device, in which the presence of one or more toxins and/or pathogens are detected, and a second level detection device. Upon detection by the first level detection device, the second level detection device performs a second level of detection in which the one or more toxins and/or pathogens are identified.

Abstract: A notification system and method of visual notification of different types of events by flashing different colors is provided, wherein the notification system includes a master controller and a notification device. The master controller is configured to communicate at least one signal. The notification device includes an enclosure accepting a plurality of conductors providing both signaling and electrical power to the notification device, and at least one strobe drive circuit configured to supply an electrical signal for periodically flashing at least one strobe. The notification device further includes a strobe system configured to flash at least one strobe, such that the strobe system flashes one of at least two different colors, and a control logic configured to determine which color of the at least two different colors to flash at least one strobe based upon the signal received from at least one of the plurality of conductors.

Abstract: An apparatus for the control of at least one safety-relevant function of a machine is described having a machine control for the control of the movements of the machine, having at least one sensor for the sensing of an object inside a monitored zone and having an evaluation unit for the setting of a danger zone and for the triggering of the safety-relevant function on the intrusion of the sensed object into the danger zone. To set the danger zone, the evaluation unit is coupled to the machine control and the evaluation unit is designed for the derivation of the parameters required for the setting of the danger zone starting from the control signals used by the machine control for the movement control of the machine. A corresponding method is furthermore described.

Abstract: Multiple parameter fire detection uses outputs from one or more radiant energy sensors in combination with outputs from smoke or thermal sensors to shorten response times to alarm while minimizing nuisance alarms. The radiant energy related outputs can be used to alter parameters of the smoke or thermal sensors. The various sensors can be displaced from one another in an alarm system.

Abstract: Techniques for monitoring operation of a flame ignitor are provided. In one embodiment, multiple inputs are received. The inputs are received from at least one of a first group of inputs and a second group of inputs. The first group includes a flame rod voltage, a stop signal for deactivation of the flame ignitor, a fuel supply interruption signal, and an air supply interruption signal. The second group includes a start signal for activation of the flame ignitor, and a flame proven signal indicating presence of a flame produced by the flame ignitor. If inputs from the first group are received, a cause of a failure of the flame ignitor is determined. If inputs from the second group are received, a reliability of the flame ignitor is determined.

Abstract: The invention relates to a control method for gas burners for providing a gas-air mixture. According to the invention, the ionization signal is only used for setting the mixing ratio dependent on the gas quality when the burner flame completely sweeps over the sensor generating the ionization signal. Outside the above-mentioned range, i.e. when the burner flame does not completely sweep over the sensor generating the ionization signal, the gas-air mixture is controlled dependent on the previously determined mixing ratio.

Abstract: A method of operating a computer for smoke and flame detection comprising the steps of: receiving digitised images of the region to be monitored; comparing pixels of one of said images with pixels of another said image according to two predetermined procedures to produce a flame present decision and a smoke present decision; and providing a fire detected signal according to said smoke present and flame present decisions.

Abstract: The present invention is directed to an apparatus for the monitoring of the combustion process within a combustion system. The apparatus comprises; a combustion system, a means for supplying fuel and an oxidizer, a device for igniting the fuel and oxidizer in order to initiate combustion, and a sensor for determining the current conducted by the combustion process. The combustion system comprises a fuel nozzle and an outer shell attached to the combustion nozzle. The outer shell defines a combustion chamber. Preferably the nozzle is a lean premix fuel nozzle (LPN). Fuel and an oxidizer are provided to the fuel nozzle at separate rates. The fuel and oxidizer are ignited. A sensor positioned within the combustion system comprising at least two electrodes in spaced-apart relationship from one another. At least a portion of the combustion process or flame is between the first and second electrodes.

Abstract: A dispersion light smoke detector has a structure for providing a definite measuring volume, the structure being formed as two light receivers or an imaging optical system for one light receiver.

Abstract: According to the invention, the ionization signal is detected at a first point of time during full-load operation and during partial-load operation, and for this first point of time a first difference is formed between the ionization signal during full-load operation and the ionization signal during partial-load operation. Furthermore, the ionization signal is detected at a second point of time during full-load operation and during partial-load operation, and for this second point of time a second difference is formed between the ionization signal during full-load operation and the ionization signal during partial-load operation. The first difference and the second difference are compared to each other and, dependent thereon, the state of the gas burner is inferred.

Abstract: The invention relates to a flame monitor for an oil- or gas-operated burner, having a photosensor which detects the optical flame radiation and an evaluation circuit which is connected downstream of said photosensor and ascertains whether the radiation received by the photosensor corresponds to that of a burning flame and, in the event of a negative result, generates a switch-off signal for the fuel supply, wherein the evaluation circuit determines the number of zero crossings of the processed signal of the photosensor within a predetermined unit of time and compares it with a predetermined limit value, a switch-off signal for the fuel supply being generated when said limit value is undershot, the signal of the photosensor, freed from the DC voltage component and noise, being processed by corresponding amplification to form square-wave pulses.

Abstract: A flame measuring device, in particular for use in a regulating device for a burner, includes an ionization electrode which is arranged in a flame region of the burner. An ac voltage is applied to the ionization electrode whereby a dc voltage component is superimposed on an ionization current that flows through a resistor connected to the ionization electrode. The flame region influences the ac voltage and the dc voltage at a blocking capacitor unequally, and allows an ac voltage component to be separated from the dc voltage component by way of a first means. The separated ac voltage component can be compared to a separated-off dc voltage component by way of a second means in order to produce a pulse width-modulated signal.

Abstract: In a flame ionization sensor type gas combustion control apparatus, the sensor is provided with a power supply which will increase the voltage as contamination build up occurs on the in-flame sensor electrode thereby keeping a constant sensor current and enabling the sensor to perform as intended even though insulative contaminant build up is present on the electrode.

Abstract: A life safety system with a micro-controller that is programmed to operate both a visual signal and an audible signal. One feature of the system is that a user is permitted to enter a temporal signaling mode for not only the audible signal, but also the visual signal. The program includes an energy saving routine that operates the visual signal in the temporal mode with an energy consumption that is substantially smaller than required for operation in a continuous mode. The temporal pattern has four cycles with one flash pulse per cycle for the first three cycles and no flash pulse for the fourth cycle.

Abstract: A smoke alarm having both an ionization detector and a photoelectric detector coupled to each other to generate an alarm signal when either of the detectors senses a potential fire. The smoke detector includes a power supply circuit having both an AC power supply and a DC battery power supply. During normal operating conditions, the AC power supply operates both the ionization detector and the photoelectric detector of the smoke alarm. Upon power interruption, the DC battery supply provides power to operate both the ionization detector and the photoelectric detector. The smoke alarm includes an interconnect that allows multiple smoke alarms to be coupled together.

Abstract: An ionic flame monitor. The flame monitor has a flame rod that produces an ionization current when the flame rod is immersed in a flame and excited by a voltage. The ionization current has a DC component and an AC component each dependent on the intensity of the flame, and a flicker frequency. The flame monitor also has a computing device that is responsive to signals representative of the flicker frequency, and the AC and DC components of the ionization current for determining the existence of the flame.

Abstract: A device for monitoring the activity of a person and/or detecting a fall suffered by a person with a view in particular to summoning help in the event of an incident hazardous to life or limb is worn by the person concerned and transmits a danger signal to a remote monitoring center. The device generates acceleration, speed and/or position signals representative of the behavior and/or the spatial attitude of the person. It establishes a probability factor representative of the probability that a dangerous situation is present from how the acceleration, speed and position signals change with time. It triggers in accordance with the value of the probability factor an alarm generator capable of causing the danger signal to be transmitted to the center.

Abstract: In an electronic ignition system for igniting a plurality of gas burners by means of a plurality of electrodes, each one being mounted adjacent with each burner for producing sparks for the ignition of each burner. A spark generating circuit connected with the electrodes in order to produce the sparks for igniting each burner. And a power source connected to the spark generating circuit. A flame sensor circuit is connected to the spark generating circuit and at least one electrode, which in a first period and once the spark generating circuit has been activated for igniting each electrode, the flame sensor circuit is operated to detect the absence of flame on the burner by means of said electrode, and once that the burner has been ignited, the electrode and flame sensor circuit are operated for sensing the presence of flame on the burner.

Abstract: A system for the detection of fire in an apparatus or device having a fan and a pump, comprising means 20, 25 for detecting the presence of a pre-condition of fire, control means 30 for deactivating the fan on detection of said precondition, and fire detector means 35 for detecting smoke or fire in the absence of air movement.

Abstract: A sensor for detecting characteristics of a flame includes a pair of electrodes that are spaced apart for passing an electric current through the flame. A pulse width modulator is coupled to the electrodes and generates an alternating current which flows through the flame. A controller operates the pulse width modulator to alter the duty cycle of the alternating current so that the average current through the flame is zero. Flame characteristic information is derived from the lengths of the positive and negative periods of the resultant alternating current.

Abstract: A flame ionization detector having a pair of spaced electrodes to which a DC voltage is applied and a flame produced between the electrodes by burning a gas whose composition is to be determined, thereby ions are produced which form an ion current between the electrodes which is representative of the gas composition to be measured. The flame detector is formed by a base plate having a first channel for inlet of the gas whose composition to be measured, a second channel for inlet of a combustion gas, a third channel connected to the first and second channels for conveying a mixture of the gases to an outlet communicating with a nozzle outlet in a ceramic plate on the base plate which faces an opening in a metal plate spaced at a predetermined distance from the ceramic plate such that the flame burns in the opening in the metal plate. An electrically conductive metal layer is disposed on the ceramic plate around the nozzle outlet therein.

Abstract: A pair of reference electrodes and a flame rod are placed in contact with charged particles in a flame produced by a burner. When a voltage is applied between the flame rod and the burner by a power source, a current (I.sub.fr) flows between them due to the flame conductivity. A potential difference (V.sub.12) between the pair of reference electrodes is detected by a potential difference detector. The dynamic flame impedance between the pair of reference electrodes is defined as the slope of the I.sub.fr -V.sub.12 relationship and is independent of I.sub.fr.

Abstract: There is disclosed a combustion-state detecting circuit of a combustion apparatus installed in a combustion chamber, including: a flame detector that has a heat-emitting device for emitting heat on application of an alternating current signal, and produces a potential difference between the current applied to the heat-emitting device and flame-electric current produced by ignition occurring within the combustion chamber; a rectifier that changes the alternating current signal provided by the flame detector into a direct current signal; an inversion amplifier that inverts the direct current signal produced by the rectifier with respect to a reference signal and increases the magnitude of the inverted signal; and a flame discriminator that compares the output signal of the inversion amplifier with a flame discriminating reference signal to determine if ignition occurs.

Abstract: A flame sensor senses the intensity of a pilot flame to determine whether main burner ignition has occurred in a gas furnace. The sensor includes a computer which is operative to trigger the sensing of the flame intensity following the provision of gas to the main burner. Circuitry associated with the computer preferably provides an indication of the pilot flame intensity to the computer through a measurement of the electrical conductivity of the pilot flame following provision of gas to the main burner.

Abstract: An ionization chamber for use in a smoke detector includes first and second outer electrodes and a non-reflective center electrode. The non-reflective center electrode can be formed as a metal electrode having a non-reflective coating or as a non-reflective, conductive plastic elements. The ionization chamber can be incorporated into combination smoke detector which includes a photoelectric sensor. A non-reflective center electrode, associated with the ion-type sensor is symmetrically located in the detector and displaced from the photoelectric sensor.

Abstract: A standalone modular flame sensor containing a multi-function power supply having outputs for both a flame rod and an ultraviolet transducer. The module also contains interfaces for the ultraviolet transducer and for the flame rod transducer. The interfaces are brought together at a summing junction arranged so that the module will work with either a flame rod, an ultraviolet transducer, or both such transducers. Output circuitry provides not only a flame-on/flame-off indication (both visible via an LED and a switch contact closure), but also provides a continuously variable signal indicating the quality of the sensed flame. The module can be used standalone with either transducer type or incorporated in a more complex control system.

Abstract: An electric control is shown for gas furnaces which controls fan motors and ignition controls based on inputs from a room thermostat (32), a high limit control and an ignition control (14) including a gas valve. A flame sense circuit (42, 42') is coupled to a microprocessor (U2) and includes a flameprobe (P1) energized by line power through a capacitor (C3) via a quick connect (QC31). A capacitor (C4) is charged by a 5 volt DC source through resistor (R12) and inputted to an inverter (U3, S2) which provides a low signal to the microprocessor when no flame is present. When a flame is present the capacitor (C4) discharges through the flame causing the inverter to change state providing a high to the microprocessor indicating that a flame is present. A diagnostic network comprising a low leakage diode (CR10) and serially connected resistor (R11) is coupled between the microprocessor (pin 8) and the input of the inverter (U3) so that the operation of the flame sense circuit can be tested.

Abstract: An apparatus and method to qualify the condition of a flame body is disclosed, where such apparatus comprises a power source, an amplifier and sensor means, where said sensor means includes two or more probes disposed in spaced apart relation so as to conduct a current and said amplifier is designed to selectively amplify the signal generated between said probes so as to isolate a selected frequency consistent with ionization of a given fuel/air mixture.

Abstract: A fire detector includes a scattered light detector unit and an ionization detector unit which are arranged upon a common base at each side of the center axis of a compartment defined by the base and a peripheral wall extending from the base. The scattered light detector includes a light source and a receiver, with their principal axes intersecting in a point of intersection which is positioned at one side of the center axis of the compartment and thus extends eccentric to the center axis. The ionization detector unit includes a holder for a preparation to be ionized, with the holder being arranged at the other side of the center axis. Suitably, a heat detector is further provided in the center axis.

Abstract: A method and apparatus of detecting the condition of a flame having an emf by electrically conducting the emf generated by the flame as a signal to a sensor through an electrically isolated conductor means and sensing with said sensor an electrical parameter which is measure of the emf of the flame and wherein the parameter is the ratio of the A.C. and D.C. signal levels.

Abstract: An integrated electronic control arrangement is disclosed in the illustrative environment of burner such as in a gas-fired furnace. The control incorporates a self-test feature which shuts down the furnace in the event of any one of a number of possible sensed faults. Self-testing occurs automatically before an attempt at ignition and during furnace operation. Proper functioning of the sensor which senses for induced air flow through the burner combustion chamber is tested prior to enabling a fan which causes that induced air flow. Air flow is confirmed by sending to and receiving back from the sensor a sequence of pulses. Should air flow not be sensed during a combustion period, combustion is terminated. A flame sensor is provided for determining the presence of a flame in the combustion chamber. During times when a flame should be present, pulse sequences are sent to and received back from the flame sensor to confirm that a flame is present.

Abstract: A system and method for igniting and monitoring a pilot flame for a burning of waste gas, such as the waste gas of an oil refinery or drilling rig, includes a current which is pulsed periodically with pulses of approximately one-second duration of electric power resulting in the outputting of an igniter electrode assembly of typically 6000 volts AC at 20 milliamperes at an alternating current frequency of typically 60 Hz. During the presence of a pilot flame, ionization of gas takes place resulting in a rectification of ignition current. The transformer has a monitoring winding outputting a signal from which a 60 Hz component is filtered out, the remaining signal having a sequence of pulses which varies between positive and negative intervals of the alternating current excitation. Comparison of the pulses provides for an indication of flame absence in the presence of equality of the pulses, and flame presence in the presence of an ineqality of the pulses.

Abstract: A safety device for an oil burner is disclosed which is capable of carrying out the detection of flame by means of a DC flame current obtained due to the rectification of flame to detect the abnormal combustion in the oil burner. The safety device includes a first flame electrode surrounded by flame of normal combustion in the oil burner and a second flame electrode arranged away from the flame and connected to an AC voltage source in a manner to be in parallel with the first flame electrode, so that the second flame electrodes cooperates with the first flame electrode to detect a failure in the flowing of a flame current through the first flame electrode or a decrease in a flame current flowing through the first flame electrode, to thereby determine any abnormal combustion in the oil burner.

Abstract: A carburetion type burning apparatus having a carburetion chamber for evaporating liquid fuel which comprises a timer for counting time from the initiation of burning operation, an ion current detecting device for measuring an ion current (if) at the time after a predetermined time counted by said timer in which the ion current in flames is stabilized, a judging device for judging existence or non-existence of an abnormal burning state by comparing the measured ion current (if) and a predetermined threshold value of ion current which causes abnormal burning condition, and an alarming device for generating an alarm when said judging device provides judgment of abnormal condition.