Diagnostic ionic flame monitor

Information

  • Patent Grant
  • 6356199
  • Patent Number
    6,356,199
  • Date Filed
    Tuesday, October 31, 2000
    24 years ago
  • Date Issued
    Tuesday, March 12, 2002
    22 years ago
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.
Description




FIELD OF THE INVENTION




This invention relates to ionic flame monitors and more particularly to such a monitor that detects all of the characteristic components of the ionization current resulting from a flame.




DESCRIPTION OF THE PRIOR ART




Ionic flame monitoring (IFM) is a time proven method of detecting the presence of flame in fossil fuel combustion system. This particular technique for flame monitoring is primarily used for determining the existence of flame in oil and/or gas fired ignition system in industrial, utility, and commercial boilers.




The ignition system is commonly referred to as an ignitor or lighter.




One example of the use of ionic flame monitoring is described in U.S. Pat. No. 4,588,372 wherein a flame rod is used to monitor the flame in a gas burning furnace to maintain a peak flame rod current. This results in incomplete combustion due to a shortage of primary air. The furnace in that patent includes a secondary air inlet that is sized to maintain excess air in the combustion chamber for complete combustion.




During the combustion of hydrocarbon fuels, free ions and charged particles are produced making the hydrocarbon-fuel flame electrically conductive. Another combustion characteristic of a hydrocarbon-fuel flame is that it pulsates resulting in time varying numbers of free electrons and charged particles. Thus the conductivity of the hydrocarbon-fuel flame will also pulsate.




As is shown in

FIG. 1

when a DC excitation voltage is applied to an electrode


10


, called an IFM rod, immersed in the hydrocarbon-fuel flame


12


an ionization current


20


is produced. The ionization current


20


has as is shown in

FIG. 2

a DC component


22


that is produced by a minimum number of free electrons and charged particles always being present in the flame.




The ionization current also has an AC component


24


that is the result of the changes in conductivity produced by the flame pulsation, and a flicker frequency


26


, also known as the pulsation frequency, arising from the pulsation of the flame. The DC intensity


22


, AC intensity


24


, and flicker frequency


26


of the ionization current


20


changes with the stability and quality of the hydrocarbon-fuel flame.




Existing ionic flame monitoring electronic packages typically measure one or more of these three characteristic components to determine if the fuel on an ignition system is burning. If flame is present a flame relay is energized and if there is no flame the relay is de-energized. The flame relay contact(s) are typically input into some form of combustion safety control system.




Ignition systems are problematic pieces of equipment subject to a number of operational problems. Historically ionic flame monitoring equipment only provides a flame relay contact output indicting flame does or does not exist. Typically, the electronic hardware cannot be adjusted and does not provide any feedback to the operators about the quality of the flame or operational condition of the firing equipment. Thus, existing ionic flame monitoring electronics are simply flame switches and nothing more.




It is a well established fact in the combustion industry that there is a relationship between the quality of flame and the ionization current in an ionic flame monitoring system. As the mixture of fuel and air comes closer to stoichometric conditions, the number of ions and free electrons increases thereby making the flame more conductive. For years boiler service engineers have used voltmeters to monitor the power supply voltage on an IFM rod and use the drop in voltage as an indicator that a good flame exists. Ionic flame monitoring is even used in analytical instruments to measure gas quality and fuel/air ratio.




The ionic flame monitor of the present invention measures all three ionization current parameters and presents these values in real time to operating and service personnel. The information is presented to the operator through a digital display as well as through a digital output port. The measurement of all three parameters and the presenting of information in real time to operators about those parameters allows the operator to track changes in the three parameters and thereby obtain an early warning that a problem is developing in the ignitor. Further the direction of the changes can be an indicator of a specific problem. Existing ionic flame monitors only use one or two of these parameters and may not display them in real time.




SUMMARY OF THE INVENTION




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 has at least first, second and third inputs. The flame monitor further has a first circuit connected to the first input of the computing device, the first circuit responsive to the ionization current for producing at the first input an AC signal representative of the flicker frequency; a second circuit connected to the second input of the computing device, the second circuit responsive to the ionization current for producing at the second input a signal having an amplitude proportional to the ionization current AC component; and a third circuit connected to the third input of the computing device, the third circuit responsive to the ionization current for producing at the third input a signal which is related to the ionization current DC component. The computing device is responsive to the signals at the first, second and third computing device inputs for determining the existence of the flame.











DESCRIPTION OF THE DRAWING





FIG. 1

shows a flame rod immersed in a flame and the ionization current produced therefrom in response to an excitation voltage.





FIG. 2

shows the DC and AC intensity and flicker frequency components of the ionization current.





FIG. 3

shows the diagram of the circuit in the ionic flame monitor of the present invention that receives the output of the flame rod of FIG.


1


.





FIG. 4

shows the flame logic which responds to the analog inputs to the microprocessor in the circuit of

FIG. 3

to produce the messages on the display of FIG.


3


and the operation of the flame relay in the circuit of FIG.


3


.





FIG. 5

shows the self test logic in the circuit of FIG.


3


.











DESCRIPTION OF THE PREFERRED EMBODIMENT(S)




Referring now to

FIG. 3

, there is shown a diagram of the circuit


30


in the ionic flame monitor of the present invention that receives the output signal from the flame rod


10


of FIG.


1


. As is shown in

FIG. 3

, the flame rod output signal enters circuit


30


through a relay


32


controlled by a microprocessor


40


. In one state the relay


32


connects the flame rod output signal to circuit


30


and in the other state the relay


32


connects a test signal


34


, to be described in more detail below, to circuit


30


. The flame rod output signal passes through an amplifier


36


to a junction


38


. Amplifier


36


has a gain which in the present embodiment for circuit


30


is manually adjustable in four steps in the normal mode of operation of the circuit


30


and under control of microprocessor


40


in a test mode of operation of circuit


30


.




The signal at junction


38


enters a first path


42


which includes a low pass filter


44


between junction


38


and input


40




c


of microprocessor


40


. The low pass filter


44


provides at the input


40




c


of microprocessor


40


a DC signal which is representative of the DC intensity of the flame in which rod


10


is immersed. In one embodiment for circuit


30


, low pass filter


44


had a cutoff upper frequency of 1 Hz.




The signal at junction


38


also enters a second path which includes between junction


38


and input


40




b


of microprocessor


40


the series combination of a high pass filter


48


, a rectifier


50


and an integrator


52


. The series combination of filter


48


, rectifier


50


and integrator


52


provide at the input


40




b


of microprocessor


40


a DC voltage level that is proportional to the AC intensity of the flame in which rod


10


is immersed. In one embodiment for circuit


30


, high pass filter


48


had a lower cutoff frequency of 5 Hz.




The signal at junction


38


also enters a third path


54


which includes between junction


38


and input


40




a


of microprocessor


40


the series combination of a bandpass filter


56


followed by a DC injection circuit


58


. The series combination of filter


56


and DC injection circuit


58


provides at the input


40




a


of microprocessor


40


an AC signal which is the AC component of the signal from flame rod


10


. In one embodiment for circuit


30


, bandpass filter


56


had a passband of 13 Hz to 800 Hz with a DC injection of 2.5 VDC. It should be appreciated that the DC injection makes the AC signal all positive so that it can be inputted to the A/D converter included in microprocessor


40


as the A/D converter in one embodiment for circuit


30


had a 0-5 VDC range.




The signals at inputs


40




a,




40




b


and


40




c


of microprocessor


40


are analog signals. In addition the microprocessor


40


also has an analog signal at input


40




d


whereby it monitors one of the voltages in the power supply included in circuit


30


.




In addition to analog input signals the microprocessor


40


has the following digital input signals:




at input


40




e


from the Push to Test pushbutton


41


—this input signal is used by the microprocessor to control


32


;




at inputs


40




f,




40




g,




40




h


and


40




i


the signals arising from the operation of the four switches


43


,


45


,


47


,


49


named Program, Change, Up and Down, respectively, which are associated with the display


60


in circuit


30


—the Program switch


43


when activated provides a signal at input


43


that the user desires to program circuit


30


and the Change, Up and Down switches


45


,


47


,


49


when activated allow the user to change the value of certain parameters such as setpoints; and




at input


40




j


from the Program Lockout slide switch


51


—when activated the signal from this slide switch causes the microprocessor


40


to lock out programming of the circuit


30


by the user.




Microprocessor


40


also includes digital outputs


40




k


,


40




l


,


40




m,




40




n


and


40




o.


The digital signal at output


40




k


is used to drive display


60


. The digital signal at output


40




l


is the drive for the flame relay


64


. The drive signal at output


401


is a pulse train which as is shown in

FIG. 3

passes through an AC to DC converter


62


before reaching flame relay


64


. The AC to DC converter


62


provides a failsafe mechanism for operation of flame relay


64


since if the microprocessor were to become non-operational the


30


signal at output


40




l


would be either a high or low level but not the pulse train that converter


62


must see in order to provide the drive signal for relay


64


.




The digital signal at output


40


m is a serial signal which is either in a format compatible with the RS-232 or RS-485 transmission standards and selector switch


66


is used to pass the signal to the proper path. The signal at output


40




n


is the input signal to test signal


34


. The signal at output


40




o


is the signal to drive the test relay


32


.




Referring now to

FIG. 4

, there is shown the flame logic


100


which responds to the analog signals at inputs


40




a,




40




b


and


40




c


of the microprocessor


40


to provide various messages on display


60


and operation of the flame relay


64


as will be described in more detail below. It should be appreciated that the logic


100


shown in

FIG. 4

is the result of the execution by microprocessor


40


of program code and that those of ordinary skill in the art can as a result of the explanation to be given below be able to write suitable program code to perform these functions.




As was described above the flame monitor of the present invention measures the DC and AC components of the ionization current


20


produced by the result of a flame


12


and the flicker frequency of the flame


12


. The AC signal at input


40




a


which is representative of the flicker frequency, the DC voltage level at input


40




b


that is proportional to the AC intensity of the flame


12


, and the DC signal at input


40




c


which is the DC component of the signal from flame rod


10


are input to an associated comparator


102


,


104


,


106


respectively.




The comparators


102


,


104


,


106


compare the signal level at their input to an associated user adjustable setpoint. The user adjusts the setpoint of each comparator using the TEST, PROGRAM, UP and DOWN pushbuttons


43


,


45


,


47


and


49


, and display


60


. The output of each of the comparators


102


,


104


and


106


is connected to an associated input of three input AND gate


108


. The output of gate


108


goes high when each of the three inputs to the gate exceed their associated user programmed setpoints.




The output of the AND gate is connected to a junction


110


where the high or low level at the gate


108


output either takes a first path


112


or a second path


114


. First path


112


includes a first user programmable time delay on pickup


116


. Delay


116


starts to time out when the output of gate


108


goes high, that is, when all three of the measured ionization current


20


parameters have exceeded their associated setpoint. Delay


116


is needed on some ignitor control systems to allow a fuel block valve closed limit switch to clear before ignitor flame is proven. If any one of the three inputs to gate


108


falls below its associated setpoint before delay


116


times out, the timer associated with delay


116


is reset to zero. In one embodiment for circuit


30


the user can program delay


116


from 0 to 10 seconds.




The output of delay


116


is connected to a junction


118


and a second user programmable time delay


120


known as the time delay on dropout whose function will be described below. After passing through delay


120


the level from AND gate


108


reaches a two input second AND gate


122


. The other input to gate


122


is a signal named “No Errors” the function of which will be explained below.




As was described above in connection with

FIG. 3

, the microprocessor


40


monitors at input


40




d


one of the voltages generated by the power supply in circuit


30


. The microprocessor also monitors various other conditions associated with circuit


30


such as the input from a watchdog timer circuit and the condition of the A/D converter included in microprocessor


40


. These inputs to microprocessor


40


are not shown in FIG.


3


. This monitoring by the microprocessor


40


occurs at predetermined intervals of time and in one embodiment for circuit


30


was set to occur at ten (10) times per second for each of the monitored conditions. The microprocessor


40


considers the occurrence of any one of the monitored conditions to be an error and thus the “No Errors” signal, which appears at one of the inputs to AND gate


120


, is an indication by the microprocessor


40


that none of the monitored conditions have occurred.




The output of gate


122


is connected to a junction


124


which is connected to a first path


124




a


to thereby provide a signal to the flame relay


64


. When all three of the measured parameters of ionization current


20


exceed their associated setpoint, the output of gate


108


goes high. If the output of gate


108


remains high the delay


116


times out and the output of delay


116


goes high at the end of that delay time. The going high of the output of delay


116


appears at the input to delay


120


and the output of delay


120


immediately goes high, that is, delay


120


does not delay the appearance at its output of a change from a low to a high level at its input.




If the No Errors signal is present at gate


122


, the output of gate


122


goes high when the output of delay


120


goes high and this energizes the flame relay


64


. Therefore the flame relay


64


is energized when all three of the measured parameters of the ionization current


20


simultaneously exceed their associated setpoint for the time associated with delay


116


.




The junction


124


is also connected to a path


124




b


which is directly connected to display


60


. If the output of AND gate


122


is a high level the display


60


shows, as a result of path


124




b,


the message “FLAME.” This message tells the user of the flame monitor of the present invention that the flame monitor has proven the presence of a hydrocarbon fuel flame


12


since all three measured parameters of the ionization current


20


have simultaneously exceeded their programmed setpoint at comparators


102


,


104


,


106


for the time associated with delay


116


, and the flame relay


64


is energized.




The junction


124


is further connected to a path


124




c


which is connected by an inverter


126


to display


60


. If one or more of three measured parameters of the ionization current


20


has not exceeded its programmed setpoint at the associated one of comparators


102


,


104


,


106


then the output of AND gate


108


remains low as does the output of AND gate


122


remain even though microprocessor


40


has not detected any errors and the flame relay


64


is deenergized. Since in this circumstance the output of AND gate


122


is a low level the display


60


shows, as a result of path


124




c


and inverter


126


, the message “NO FLAME.” Thus when flame relay


64


is deenergized and all three of the measured parameters of the ionization current


20


have not each simultaneously exceeded their associated setpoints the display


60


shows the “NO FLAME” message.




As was described above, when the three measured parameters of the ionization current


20


have each simultaneously exceeded their associated programmed setpoint signals and the delay


116


has timed out and there are not any errors detected by microprocessor


40


the flame relay


64


is energized. If one or more of the three measured parameters should thereafter fall below its associated setpoint, the output of gate


108


immediately goes low. The flame relay


64


is, however, not immediately deenergized because of the time delay in dropout


120


which prevents the change from a high to a low level at gate


108


from appearing at the output of gate


122


until delay


120


times out. The timer of delay


120


is reset to zero if the output of gate


108


returns to a high level before delay


120


times out. The time delay on dropout


120


eliminates nuisance trips of the ignitor when short duration perturbations occur in the ignitor flame. In one embodiment of circuit


30


, delay


120


was programmable from 0 to 2.0 seconds.




The output of gate


122


at junction


124


is also connected by path


124


d to one input of a two input AND gate


128


. The other input to gate


128


is connected by an inverter


130


to junction


118


. When the output of AND gate


108


has changed from a high level to a low level as a result of one or more of the three measured parameters falling below its associated setpoint and delay


120


is not yet timed out, the output of AND gate


128


is at a high level and the display


60


shows the message “FLAMEOUT.” Therefore the appearance of “FLAMEOUT” on display


60


indicates to the user that the flame monitor of the present invention has lost proven flame and is in the time delay cycle where the “FLAME” display may be restored as the flame relay


64


is still energized.




As was described above, when all three of the measured parameters of the flame


12


have each simultaneously exceeded their associated setpoint, the output level at AND gate


108


becomes a high level. The appearance of that high level at gate


122


is delayed by the programmable delay of time delay on pickup


116


. During the timing out of this delay the display


60


should provide a message to the user that delay


116


has not yet timed out. The appearance of “ON DELAY” in display


60


is that message. As is shown in

FIG. 4

, the output of AND gate


108


is connected to one input of a two input AND gate


132


. The other input to gate


132


is connected by inverter


130


to junction


118


which is at a low level when delay


116


has not yet timed out. Thus, when delay


116


is timing out the output of gate


132


provides the high level that causes display


60


to show the “ON DELAY” message.




The flame monitor of the present invention further includes as part of circuit


30


the logic shown on

FIG. 5

to allow the user to self test the flame monitor. It should be appreciated that the logic


200


shown in

FIG. 5

is the result of the execution by microprocessor


40


of program code and that those of ordinary skill in the art can as a result of the explanation to be given below be able to write suitable program code to perform these functions.




The self test logic


200


is initiated only when the user presses the TEST pushbutton


41


shown in

FIG. 3

for a predetermined period of time and the flame monitor has not proven a flame, that is, display


60


shows the message “NO FLAME.” These two signals are two of the input signals to three input AND gate


202


.




The output of AND Gate


204


when high indicates that the self test was successful. The high out of gate


204


passes through a delay


222


having a time T


1


+Z, where Z as is described below is the time in seconds to complete all three parts of the self test and T


1


is the time associated with first delay


206


, then through a delay


250


having a time T


2


and finally through an inverter


252


to the third input of AND gate


202


. Therefore, a new self test will not be initiated after the successful completion of a previous self test until the Time T


2


of delay


252


times out.




The output of gate


202


is connected through first delay


206


to a junction


208


. Delay


206


delays the high level which has appeared at the output of gate


202


from appearing at junction


208


for the predetermined time T


1


. The predetermined time T


1


requires that the user hold the TEST pushbutton


41


depressed for at least that period of time before the self test procedure is initiated. If the user releases the TEST pushbutton


41


at any time before the self test is completed the self testing is terminated. If the user holds the TEST pushbutton depressed for time T


1


, the high level at the output of gate


202


appears at junction


208


and a suitable message appears on one line of the display


60


to inform the user that circuit


30


has entered the self test mode. In one embodiment for the flame monitor of the present invention the display


60


has two lines of display and the message that appears on line 2 of the display to indicate that circuit


30


is in the self test mode is “#TESTING”, and the predetermined delay time T


1


of delay


206


was set at five (5) seconds.




When the time T


1


of delay


206


times out, the high level at junction


208


causes the test relay


32


to be energized and the flame rod


10


to be disconnected from the flame monitor and the gain of amplifier


36


to be temporarily reset to a known setting. As is shown on

FIG. 3

, the microprocessor provides at output


40




o


the signal to energize the flame relay


32


.




As was described in connection with

FIG. 3

, an AC/DC test signal


34


is input to circuit


30


when the flame monitor is in the self test mode of operation. As is shown in

FIG. 3

, the microprocessor provides at output


40




n


the AC/DC test signal.




Junction


208


is connected to a first comparator


210


which compares the DC test signal which is representative of the DC intensity that would be received from a flame rod


10


to fixed upper and lower limits that represent the acceptable minimum and maximum values for the DC intensity.




Junction


208


is also connected through a delay


216


to a second comparator


212


which compares the AC test signal which is representative of the AC intensity that would be received from a flame rod


10


to fixed upper and lower limits that represent the acceptable minimum and maximum values for the AC intensity. The signal at junction


208


is delayed from appearing at the input to comparator


212


for the predetermined time T


1


+X of delay


216


. In one embodiment for the flame scanner of the present invention, the predetermined time X of delay


216


was set at five (5) seconds.




Junction


208


is further connected through a delay


218


to a second comparator


214


which compares the flicker frequency test signal to fixed upper and lower limits that the acceptable minimum and maximum values for the flicker frequency. The signal at junction


208


is delayed from appearing at the input of comparator


214


for the predetermined time T


1


+Y of delay


218


. In one embodiment for the flame scanner of the present invention, the predetermined time Y of delay


218


was set at ten (10) seconds.




During each of the three parts of the self test an appropriate message appears in the display to inform the user about that part of the test. In the one embodiment for circuit


30


where display


60


has two lines that message appears in line one.




The logic


200


includes selectors


254


,


256


and


258


each of which have three inputs,


254




a-c,




256




a-c


and


258




a-c.


Input


254




a,




256




a


and


258




a


are the control input to each selector. The level of the control input of each selector


254


,


256


,


258


determines if the output of the selector is either the input


254




b,




256




b,




258




b


or the input


254




c,




256




c,




258




c.


When the level of the control input is low the output of each selector is the associated input


254




c,




256




c,




258




c


and when the level of the control input is high the output of each selector is the associated input


254




b,




256




b,




258




b.






Control input


254




a


of selector


254


is connected to junction


208


. Input


254




b


is connected to the output of selector


256


. Input


254




c


is connected to a signal named “NORMAL OPERATION.” When circuit


30


is not in the self test mode of operation the signal at junction


208


is at a low level and the output of selector


254


is the NORMAL OPERATION signal which allows line one of the display


60


to display the messages associated with the normal operation of circuit


30


. When circuit


30


is in the self test mode of operation the signal at junction


208


is at a high level and selector


254


provides to line one of display


60


the message that appears at input


254




b


from selectors


256


and


258


.




The control input


256




a


of selector


256


is connected to the output of delay


216


. The input


256




b


is connected to the TEST AC input of comparator


212


. The input


256




c


is connected to the output of selector


258


. When circuit is in the test mode and the output of timer


216


is low, the display


60


displays in line one the message that is at the output of selector


258


. When circuit


30


is in the test mode and the output of delay


216


is high, line one of display


60


displays the AC value.




The control input


258




a


of selector


258


is connected to the output of delay


218


. The input


256




b


is connected to the TEST FREQ input of comparator


214


. The input


256




c


is connected to the TEST DC input of comparator


210


. When circuit


30


is in the test mode and the timer


218


has not timed out, the output of selector


258


is the DC intensity. When circuit


30


is in the test mode and output of delay


218


has timed out, the output of selector


258


is the FREQ value.




Therefore, when circuit


30


is in the test mode the following displays appear in line one of display


60


:




a) during the time from T


1


to T


1


+X, the DC intensity;




b) during the time from T


1


+X to T


1


+Y, the AC intensity; and




c) during the time from T


1


+Y until the signal level at junction


208


next goes low, the FREQ value.




The output of each of comparators


210


,


212


,


214


is connected through an associated inverter


224


,


226


,


228


, respectively to one of the two inputs of an associated two input AND gate


260


,


262


,


264


, respectively. When the DC intensity, the AC intensity and the flicker frequency are each during their test within their associated upper and lower limits, the output of each of gates


260


,


262


,


264


is a low.




The other input of gates


260


,


262


,


264


is connected to the input of the associated comparator


210


,


212


,


214


that receives the signal level at junction


208


. When one of the parameters, DC intensity, Ac intensity, flicker frequency is undergoing its test the signal level at this other input of the associated gate


260


,


262


,


264


is a high level. When a parameter is not undergoing its test the signal level at this other input of the associate gate


260


,


262


,


264


is a low level. Thus when a parameter, for example, DC intensity is undergoing its test, the output of the associated gate, which is


260


for the DC intensity test, is a high level only if the parameter does not pass its test and is a low level at all other times during the self test mode of operation of circuit


30


.




The gates


260


,


262


,


264


are each connected to an associated input of three input OR gate


220


. Since the output of gates


260


,


262


,


264


are all a low level during the self test mode of operation unless the associated parameter does not pass its test, the output of OR gate


220


is a low level if during the self mode of operation each of three parameters passes its associated test and is a high level only if one or more of the parameters does not pass its test.




The output of OR gate


220


is connected to one input of two input AND gate


232


. The other input to AND gate


232


is the signal level at junction


208


. The output of gate


232


when a high level allows the display


60


to show the message “#FAIL” in line two when display


60


is embodied as the two line display. Since the input of gate


232


connected to the output of OR gate


220


is only a high level if one or more of the tested parameters has not passed its associated test, the message “#FAIL” only appears in the display


60


if one or more of the tested parameters has not passed its test. Upon seeing this message the user of the flame monitor should release the Test pushbutton


41


.




The output of gate


232


is connected by an inverter


266


to one of the three inputs of AND gate


204


. Since the output of AND gate


232


during the self test mode of operation is only a high level if one or more of the tested parameters does not pass its associated test, the output of gate


204


is always a high level unless one of more of the three parameters does not pass its associated test.




The appearance of a high level at the output of gate


204


is connected to a delay


222


which has a delay time equal to the time of delay


206


plus a predetermined amount of time Z. Once delay


222


times out the high level at its input appears at its output and the flame relay


64


is momentarily energized and the display


60


shows the message “#RELAY” to tell the user that the self test was successfully completed. The high level at the output of delay


222


is connected by an inverter to one input of three input AND gate


202


to clear the self testing logic. In the one embodiment for the flame monitor of the present invention where the time of delay


206


is five seconds the predetermined amount of time Z for delay


222


was set at fifteen seconds.




It is to be understood that the description of the preferred embodiment(s) is (are) intended to be only illustrative, rather than exhaustive, of the present invention. Those of ordinary skill will be able to make certain additions, deletions, and/or modifications to the embodiment(s) of the disclosed subject matter without departing from the spirit of the invention or its scope, as defined by the appended claims.



Claims
  • 1. An ionic flame monitor comprising:a. a flame rod that produces an ionization current when the flame rod is immersed in a flame and excited by a voltage, said ionization current having a DC component and an AC component each dependent on the intensity of said flame, and a flicker frequency; b. a computing device having at least first, second and third inputs; c. a first circuit connected to said first input of said computing device, said first circuit responsive to said ionization current for producing at said first input an AC signal representative of said flicker frequency; d. a second circuit connected to said second input of said computing device, said second circuit responsive to said ionization current for producing at said second input a signal having an amplitude proportional to said ionization current AC component; and e. a third circuit connected to said third input of said computing device, said third circuit responsive to said ionization current for producing at said third input a signal which is related to said ionization current DC component; said computing device responsive to said signals at said first, second and third computing device inputs for determining the existence of said flame.
  • 2. The flame monitor of claim 1 wherein said computing device has a setpoint associated with each of said signals at said first, second and third inputs and said computing device proves the existence of a flame when all three of said signals each exceed said associated setpoint.
  • 3. The flame monitor of claim 1 further comprising a display.
  • 4. The flame monitor of claim 3 wherein said computing device has a setpoint associated with each of said signals at said first, second and third inputs and said computing device sends to said display a message that said flame exists when all three of said signals each exceed said associated setpoint.
  • 5. The flame monitor of claim 1 wherein said computing device has a setpoint associated with each of said signals at said first, second and third inputs and a first delay associated with a falling below of any one or more of said three of said signals fall below said associated setpoint after all three of said signals have simultaneously each exceeded said associated setpoint.
  • 6. The flame monitor of claim 5 wherein said first delay is activated when at least one of said three signals falls below said associated setpoint after all three of said signals have simultaneously each exceeded said associated setpoint.
  • 7. The flame monitor of claim 6 further comprising a display.
  • 8. The flame monitor of claim 7 wherein said computing device sends to said display an appropriate message when said first delay is timing out.
  • 9. The flame monitor of claim 6 wherein said computing device determines that there is not any flame when said first delay times out and at least one of said one or more of said signals that fell below said associated setpoint did not exceed said associated setpoint at any time during said activation of said first delay.
  • 10. The flame monitor of claim 1 wherein said computing device has a setpoint associated with each of said signals at said first, second and third inputs and a second delay associated with all three of said signals simultaneously exceeding said associated setpoint.
  • 11. The flame monitor of claim 10 wherein said second delay is activated when all three of said signals first simultaneously exceed said associated setpoint.
  • 12. The flame monitor of claim 11 wherein said second delay times out when all three of said signals simultaneously exceeds said associated setpoint for the period of said second delay.
  • 13. The flame monitor of claim 11 further comprising a display.
  • 14. The flame monitor of claim 12 wherein said computing device sends to said display an appropriate message when said second delay times out.
  • 15. The ionic flame monitor of claim 1 wherein said ionic flame monitor further comprises an input for receiving said ionization current and an amplifier having a gain adjustable in a predetermined number of steps between said input and said first, second and third circuits.
  • 16. The ionic flame monitor of claim 15 wherein said gain of said amplifier is manually adjustable.
  • 17. The ionic flame monitor of claim 15 wherein said gain of said amplifier is adjustable under control of said computing device.
  • 18. The ionic flame monitor of claim 1 further comprising means connected to said computing device which when activated disconnects said ionization current from said computing device and provides a test signal representative of an ionization current internal to said flame monitor to said computing device for testing said flame monitor.
  • 19. The ionic flame monitor of claim 18 wherein said means for providing said internal test signal comprises a switch which when activated disconnects said ionization current from said computing device and connects said test signal to said computing device.
  • 20. The ionic flame monitor of claim 19 further comprising a test signal source connected to said means for providing said internal test signal.
  • 21. The ionic flame monitor of claim 18 said means for providing said internal test signal includes a predetermined time delay which must elapse from initiation of an internal test of said flame monitor before said test signal is applied to said computing device.
  • 22. The ionic flame monitor of claim 18 further comprising a display connected to said computing device for displaying the results of said internal test of said flame monitor.
  • 23. The ionic flame monitor of claim 18 wherein said internal test is performed in a predetermined sequence of steps to test the response of flame monitor to said internal signal representative of an ionization current.
  • 24. The ionic flame monitor of claim 23 wherein said predetermined sequence of steps for said internal test first tests said flame monitor for responsiveness to the DC intensity of said internal signal representative of an ionization current.
  • 25. The ionic flame monitor of claim 18 wherein said internal test tests the response of said flame monitor for responsiveness to the DC intensity, AC intensity and flicker frequency of said internal signal representative of said ionization current.
  • 26. The ionic flame monitor of claim 25 further comprising a display connected to said computing device for displaying the results of said internal test of said flame monitor, said display indicating a failure of said internal test if said responsiveness of said flame monitor to any one or all of said DC intensity, AC intensity and flicker frequency tests of said internal signal representative of said ionization current does not meet an associated predetermined criteria for passing said test.
  • 27. The ionic flame monitor of claim 1 wherein said computing device has an input/output for connection to a remote computing device to provide information about said flame monitor to said remote computing device and to receive information from said remote computing device.
  • 28. The ionic flame monitor of claim 27 wherein said input/output for connection to a remote computing device is selected between one or more interfaces for transmitting information between said flame monitor computing device and said external computing device.
  • 29. The ionic flame monitor of claim 28 wherein one or more interfaces are a first interface that meets the RS-232 transmission standard and a second interface that meets the RS-485 transmission standard.
  • 30. The ionic flame monitor of claim 1 wherein said computing means monitors the integrity of said flame monitor by monitoring one or more parameters internal to said flame monitor when said flame monitor is determining the existence of said flame.
  • 31. The ionic flame monitor of claim 30 wherein said integrity monitoring occurs a predetermined number of times per second.
US Referenced Citations (6)
Number Name Date Kind
3740574 Taylor Jun 1973 A
4107657 Nishigaki et al. Aug 1978 A
4370557 Axmark et al. Jan 1983 A
5073104 Kemlo Dec 1991 A
5472337 Guerra Dec 1995 A
5952930 Umeda et al. Sep 1999 A