Flame sensor verification
First Claim
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1. A system for detecting the presence and quality of a flame being produced by an electrically grounded burner of a furnace, said system comprising:
- an electrode mounted in the path of a flame produced by the burner;
an alternating current voltage source connected through a first capacitor and a first resistor to said electrode, said alternating current voltage source causing current to flow through the electrode and through a flame impinging on the electrode to the burner, the current flow through the flame producing an attenuated voltage condition at the electrode caused by the relative conductivity of the flame for positive versus negative voltage fluctuation of the alternating current voltage;
a second resistor connected at one end to a junction between said first resistor and said first capacitor;
a second capacitor connected to the opposing end of said second resistor, said second capacitor in combination with said first capacitor and said second resistor defining a second current path to ground from the alternating current voltage source, said second capacitor charging over time to a capacitance voltage level indicative of the attenuated voltage condition at the electrode; and
a processor having an input for sensing when the second capacitor has reached the capacitance voltage level indicative of the attenuated voltage condition at the electrode, said microprocessor including means for measuring the time the second capacitor takes to achieve the capacitance voltage level indicative of the attenuated voltage condition at the electrode.
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Abstract
Method and apparatus are disclosed for checking the responsiveness of a circuit which senses the presence of a flame produced by a burner within a furnace. A programmed processor associated with the circuit measures the time the circuit takes to indicate the presence of a flame. A warning is generated when the measured time exceeds a predetermined allowable time. The allowable time is determined by taking into account the decreased responsiveness of an electrode that indicates the presence of the burner flame.
69 Citations
13 Claims
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1. A system for detecting the presence and quality of a flame being produced by an electrically grounded burner of a furnace, said system comprising:
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an electrode mounted in the path of a flame produced by the burner; an alternating current voltage source connected through a first capacitor and a first resistor to said electrode, said alternating current voltage source causing current to flow through the electrode and through a flame impinging on the electrode to the burner, the current flow through the flame producing an attenuated voltage condition at the electrode caused by the relative conductivity of the flame for positive versus negative voltage fluctuation of the alternating current voltage; a second resistor connected at one end to a junction between said first resistor and said first capacitor; a second capacitor connected to the opposing end of said second resistor, said second capacitor in combination with said first capacitor and said second resistor defining a second current path to ground from the alternating current voltage source, said second capacitor charging over time to a capacitance voltage level indicative of the attenuated voltage condition at the electrode; and a processor having an input for sensing when the second capacitor has reached the capacitance voltage level indicative of the attenuated voltage condition at the electrode, said microprocessor including means for measuring the time the second capacitor takes to achieve the capacitance voltage level indicative of the attenuated voltage condition at the electrode. - View Dependent Claims (2, 3, 4, 5)
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6. A process for checking the responsiveness of a system for sensing the presence and quality of a flame generated by a burner within a furnace, the system including an electrode which experiences an attenuated A.C. voltage condition when a flame from the burner impinges on the electrode, the system furthermore including a capacitor which charges to a voltage level indicative of the attenuated voltage condition experienced by the electrode when a flame from the burner impinges on the electrode, said process comprising the steps of:
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causing an alternating current to flow through the electrode and through a flame impinging on the electrode; discharging the capacitor for a predetermined period of time; allowing the discharged capacitor to again begin charging as a result of the flame impinging on the electrode; initiating a clock timer following said step of allowing the discharged capacitor to again begin charging; reading the clock timer when capacitor has changed to a voltage level indicative of the attenuated voltage condition experienced by the electrode; comparing the read clock time to an allowable period of elapsed clock time if the capacitor has charged to the voltage level indicative of the attenuated voltage condition of the electrode; and displaying a message indicating when the read clock time is greater than the allowable period of time. - View Dependent Claims (7)
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8. A system for checking the presence and quality of a flame being produced by a burner in a furnace, said system comprising:
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an electrode mounted in the path of the time produced by the burner; an alternating current voltage source, connected to said electrode, for causing current to flow through the electrode and through the flame to the burner acting as a ground for the current flow when a flame is present; a resistance-capacitance circuit for filtering the alternating current voltage being applied to the electrode, said resistance capacitance circuit including a capacitor which normally experiences a voltage build up in response to current initially flowing through the electrode and through the flame to the burner; a processor for measuring the time that the capacitor in the resistance-capacitance circuit takes to build up sufficient voltage to indicate the presence of a time, said processor generating a message indicating when the measured time exceeds a predetermined time during which the capacitor is to have built up sufficient voltage to indicate the presence of a flame; and a display for displaying the message generated by said processor indicating when the measured time exceeds a predetermined period of time during which the capacitor is to have built up the sufficient voltage to indicate the presence of a flame. - View Dependent Claims (9, 10)
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11. A process for checking the responsiveness of a circuit which detects the presence and quality of a flame produced by a burner in a furnace, said process comprising the steps of:
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generating an A.C. voltage potential between an electrode and the burner of the furnace; filtering an A.C. voltage waveform upstream of the electrode thorough a resistor and a capacitor; measuring the time it takes to build up a voltage in the capacitor due to the voltage condition occurring at the electrode when a flame is present; determining when the measured time exceeds a predetermined period of time during which the build-up of voltage in the capacitor is to occur; and displaying a warning indicating that the circuit for detecting the presence and quality of a flame is exceeding the predetermined period of time. - View Dependent Claims (12, 13)
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Specification