CA2135776A1 - Flame rectification sensor employing pulsed excitation - Google Patents
Flame rectification sensor employing pulsed excitationInfo
- Publication number
- CA2135776A1 CA2135776A1 CA002135776A CA2135776A CA2135776A1 CA 2135776 A1 CA2135776 A1 CA 2135776A1 CA 002135776 A CA002135776 A CA 002135776A CA 2135776 A CA2135776 A CA 2135776A CA 2135776 A1 CA2135776 A1 CA 2135776A1
- Authority
- CA
- Canada
- Prior art keywords
- flame
- signal
- alternating voltage
- voltage
- generator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
- F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2229/00—Flame sensors
- F23N2229/12—Flame sensors with flame rectification current detecting means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2231/00—Fail safe
- F23N2231/10—Fail safe for component failures
Abstract
2135776 9428354 PCTABS00034 A flame rectification type flame sensor circuit and method in which a generator (51) injects periodic pulses of alternating voltage into a flame region (58), the voltage across the flame region (58) being processed by a filter/amplifier (60) which, in proper operation, produces a non-zero output signal only during the time a flame (58) is present and a pulse of alternating voltage is being supplied by the generator (51). Final indication of a flame (58) is produced only if a non-zero output signal occurs during the time a pulse of alternating voltage is being supplied, and not during the time between successive pulses of alternating voltage.
Failure of an electrical component in the filter/amplifier (60) is indicated if a non-zero output signal occurs during the time between successive pulses of alternating voltage.
Failure of an electrical component in the filter/amplifier (60) is indicated if a non-zero output signal occurs during the time between successive pulses of alternating voltage.
Description
~;VO 94128354 . 2 ~ 7 7 l; PCTIUS94/06010 - I -FLAME RECTIFICATION SENSOR EMPLOYING PULSED EXCITATION
BACKGROUND OF THE INVENTION
The present invention relates generally to flame detectors and detection methodsbased on electric current rectification properties of a flame, and, more specifically, to 5 such a detector and detection method employing periodic pulses of alternating current excitation in a manner to permit detection of inoperable electrical components which could result in flame detection errors.
Combustion systems, such as those used in furnaces, boilers and other appliances in which controlled burning takes place, commonly utilize automatic control 0 systems to ignite, control the flow of, and monitor the combustion of a fuel, such as natural gas, oil, etc. One of the required functions for such an automatic control system .
is to monitor the flame, and, in its absence, terminate the flow of the fuel to avoid serious hazards. Thus, it is essential that any flame detection apparatus in such a system be designed and constructed to operate in a highly reliable manner.
IS One well known technique for detecting the presence of a flame is based on electrical properties associated with the fla ne. As a flame burns, it produces an ioniæd region in its vicinity, thereby providing an electrically conductive medium. This property can be utiliæd in conjunction with a probo placed into the flame, and agrounded metal burner to produce a usable electrical signaL If such apparatus is-~ 20 conslruc~d with an effective grounded burner area greater than the effective probe area, typically in at least a 4 to 1 ratio, the flame will exhibit electrical characteristics som what similar to those of a diode in series with a 10 megobm resistor. If an ; alt~nabng current signal is injected into the flame by the probe, the signal will be rcbfied by the flame. Appropriate filtering and amplification circuitry may then be 2S employed to extract the rectified sig~al.
~ Two practical applications of this technique are illustrated in Figures 1 and 3, ; which are schematic diagrams of previously known systems. Figure 1 illustrates a shunt topology implementation in which an alternating current drive generator is connected dectrically in parallel with the burnerMa ne/probe system. If a flame is present, a 30 voltage divider will be formed during the positive excursions of the AC drive signal.
- This will have the effect of developing a negative bias on the AC signal at the input of a : :
WO 94/28354 C~ 3~ 7 ~J PCT/US94/06010 --flame filter/amplifier generally designed to remove the AC component, leaving only a DC signal indicative of the presence or absence of a flame.
Figure 3 illustrates a series topology implementation of the prior flame rectification detection technique. The requirements for the detector system components s are generally the same as for those in the shunt topology implementation, excepl that current, rather than voltage, signals are processed.
Because the circuitry for performing the filtering and amp}ifying is considered safety related, industry standards require that first and second level failure modes must not compromise its function. This requirement has led to the use of redundant circuit o elements, adding expense, leakage paths and crowded circuit board conditions. Thus, a need exists for a flame detector design which provides fail safe operation without ~ 1 requiring redundant components.
i SI~MMARY OF THE INVENTION
The invention is a flame sensing system and method based on electric current 5 rectification properties of a flame, the system and method utilizing pulsed alternating current excitation in a manner to avoid flame indication errors resulting from electrical component failures, without requiring redundant components. The system includes a drive generator for exciting a pair of electrodes in a fla ne region with periodic pulses of altemating current which are imparted with an electrical bias if a flarne is present. A
20 filter/amplifier attenuates the AC component of current between the electrodes, leaving a DC signal corresponding to presence or absence of a flame. Output logic ;s operable to indicate presence of a flame only if the DC signal corresponds to presence of flame during the time the electrodes are being excited with a pulse of alternating current, and does not correspond to presence of a flame during ~e time between excitation with 25 successive pulses of alternating current. A DC signal corresponding to presence of a flame during the time between excitation of the electrodes with successive pulses of alternating cu~rent indicates failure of a system component, thenby permitting fail safe operation.
A specific objective of the invention is to provide a flame detector design which 30 requires a minimurn number of components in the sensitive, high impedance portion of the filter/amplifier circuitry.
~fr.. . ~
WO 94/28354 . ~ 7 7 ~ PCT/US94/06010 A further objective is to provide a desi'gn which allows reliable detection of loss of flame in a substantially shorter time than the current industry standard of 0.8 seconds.
Yet, a fi~rther objective is to provide a design which permits detection of failure of critical components in the filter/amplifier circuitry substantially any time during its s operation, and not just at the beginning of a flame cycle.
ps~IEF DESCRIPTION OF THE DRAWlNGS ' ' Figure 1 is a schematic diagram of a prior art rectification type flarne sensor employing a shunt circuit topology design.
Figure 2 is a representation of signal waveforms at indicated points in the sensor 0 of Figure 1.
Figure 3 is a block diagram of a prior art rectification type flame sensor employing a series circuit topology design.
Figure 4 is a block diagram of a rectification type flame sensor in accordance 'with the applicants' invention.
IS Figure 5 is a representation of signal waveforms at various points in the system of Figure 4, and showing the normal system output, as well as system outputs when cc~in component failures exist.
Figure 6 is a circuit diagram of the flame sensor of Figure 4.
~ Figure 7 is a flow diagram of certain logic operations accomplished in a portion - ~ 20 of the circuit of Fig~ure 6.
- ~ P,SCRIPTION OF THE PREFF,RRED EMBODIMENT
- ~ Refernng to Figure 1, réference numeral 10 generally identifies a shunt topology form of a prior art flame sensing system based on the electric current rectification cbar~cteristics of a flame. System 10 is shown as including an alternating current drive 2S generator 11 in series with a resistor 13 connected across a burner apparatus having a flame sensing electrode. Both generator 11 and the burner apparatus are electrically ferenced to ground 12.
~' With particular Kference to the burner system, metal burner apparatus 14 is clectrically connected to ground 12, ~e burner apparatus being adapted to support a ~30 flamc 15 in a flame region. A flame probe 16, which extends into the flame region, is connected to generator 11 ~rough resistor 13 so as to be excited by the altemating current produced by the generator Burner apparatus 14 conventionally is constructed to ., ~WO 94/283.~4 PCT/US94/06010 2133~ 4 .3 have a effective grounded area of at least four times the effective area of probe 16, thereby, in conjunction with flame 15, effectively forming an electrical rectifier. As shown in dashed line symbols in parallel with burner 14 and probe 16, the burnerMame/probe arrangement electrically roughly appears as a resistor 17 in series .~ 5 with a diode 18, the resistor having a high resistance value, typically on the order of 10 megohms.
A node 19 between resistor 13 and probe 16 is connected to a filter/amplifier 20.
Filter/amplifier 20 includes a first resistor 21 between node 19 and a node 22, which is connected to the gate electrode of a field effect transistor (FET) 23.
loAs shown in Figure 1, three resistors, identified by reference nurnerals 24, 25 and 26, and a capacitor 27 are connected in parallel between node 22 and ground 12.
FET 23 is connected through its source and drain electrodes in series with a resistor 28 between a positive voltage supply terminal 30 and ground 12. The output signal of filterlamplifier 20 is produced at a temlinal 31 cormected between FET 23 and resistor 15 28.
In operation, the burnerMame/probe system imparts a negative bias to the AC
excitation signal. Resistor 21 and capacitor 27 form a low-pass filter which extracts the DC component from ~e rectified excitation signal. FET 23 detects the DC level at the - output of the fi1ter. In particular, FET 23 becomes nonconducting when the signal at 20 node 22 corresponds to presence of a flame.
A bleed resistor in parallel with capacitor 27 is required to drain off the charge on the capacitor when the flame is lost. This is a critical function, since the automatic control system must act to shut off the flow of fuel in the absence of a flame to avoid a ha~dous situation. Therefore, redundant resistors 24, 25 and 26 are provided so ~at, 25 in the absence of flame, the charge on capacitor 27 will drain off, even if two of these resistors fail in an open circuit condition.
The foregoing requirement adds cost and complexity to the circuit. Further, because the flame presents a high impedance, extraordinary techniques must be used in the filtering and amplifying circuitry. In particular, the impedances of the filter 30 elements must also be in the 50 megohm range to avoid excessive loading of the 10 megohm impedance of the flame. The redundant components add potentially problematic leakage paths, thereby compromising circuit reliably, and limiting its use.
-~ WO 94/283S4 ~ 1 r! .3 7 7 ~ PCTIUS94/06010 .~ .
The wavefo~ns which occur at designàted points in the flame sensor of Figure 1 during its operation are illustrated in Figure 2, in which the top waveform indicates a short interval during which flame 15 is present. The second waveform illustrates a relatively high frequency AC signal produced by drive generator 11, which is present at 5 point A in the sensor of Figure 1. The third waveform in Figure 2 shows that during the interval when flame 15 is present, the excitation signal is rectified to produce at point B
a voltage having attenuated positive values. This signal forms the input to .~
filter/amplifier 20 which removes the AC component, as has been described, to provide . 1 at point C a signa~ as illustrated by the bottom waveform in Figure 2. This signal is lo indicative of presence or absence of a flame.
In the prior art series topology implementation of Figure 3, various elements corresponding to those in Figure 1 are realranged such that drive generator 11' is connected in series between probe 16' and filterlamplifier 20'. This series combination is, in turn, effectively connected in series with burner 14' and flame 15' between ground 15 12' and output terminal 31'.
By way of context and background for the applicants' invention, two of the design requirements for the control system under consideration were that it be polarity insensitive, and that it operate in the presence of condensed moisture. These requirements particularly impact the flame sensor circuitry. When water condenses on 20 higb impedance filter/amplifier components, leakage paths are created physically across the bodies of the components and between the various electrical nodes. These leakage patbs can completely attenuate the flame signal. This situation can be improved by (1) reducing the nurnber of components across which leakage paths can occur, (2) msximizulg physical separation of the components, both lead to lead and node to node, 2S and (3) driving the filter/amplifier with as large a signal as possible.
For tbe particular application for which the disclosed implementation was designed, a transformer based voltage step up circuit is employed to provide polarity insensitivity. However, it is pointed out tbat the inventive concept is useful in applications not requirhg polarity insensitivity, and that polarity insensitivity can be 30 provided by means otber than a transformer based step up circuit.
By designing the disclosed step up circuit to produce as high a frequency as possible, the cost of magnetic components is minimized~ along with the number of poles ¦ wo 94/28354 ~ PCT/US94/06010 required in the filter/amplifier. Minimizing the number of filter poles also minimizes the number of high impedance nodes and components, and allows the remaining components to be spread out as much as possible within the packaging constraints.
The upper frequenc~ limit is determined by the stray capacitance to ground of 5 the flame detection probe system and of the flame itself. This capacitance, when ,:
combined with the series impedance of the flame sensor power supply, forrns a first order low pass filter. Experimental results indicate that 40 KHz is the upper limit. 30 KHz is a practical compromise between design margin and magnetic component costs.
An additional advantage of the high operating frequency is that it reduces the lo sensor response time to loss of flame. It also perrnits use of a single pole filter having a short decay response time. The short decay time allows a design approach which eliminates the need for the FMEA-required triple parallel high resistance resistors otherwise required for reliability in draining offthe charge from the filter capacitor. In particular, control electronics, which will be described in greater detail hereinafter, turns lS the high frequency, high voltage flame probe excitation signal on and off at a 5 Hz rate.
In the presence of a flarne, the control electronics processor will see a similar S Hz signal at the output of the flarne amplifier. If the single bleed resistor opens, the capacitor will remain charged and the control electronics will deterrnine that the flarne probe detection signal no longer matches the flame probe drive signal. Such operation 20 may also be used to detect a number of other component ~ailures.
Turning to Figure 4, reference numeral 50 generally identifies a shunt topology version of a flame sensor in accordance with the applicants' invention. System 50 includes an alternating current drive generator 51 referenced to an electrical ground 52, and operable to produce an alternating current excitation signal on an output conductor 25 53. Generation of the excitation signal is controlled by a signal on a control conductor 54 provided by co~trol electronics 55. As will be described hereinafter, the control electronics are designed to produce a square wave, shown as waveform D in Figure 5, having a predeterminéd repetition rate. As previously indicated, repetition rate of five r~tions per second,~for the control signal, and a frequency of 30 KHz for the 30 alten~ating curTent excitation signal, have been found suitable for the sensor of Figure 4.
In the disclosed implementation, the excitation signal on conductor 53 is supplied through a resistor 56 to a flame probe 57 which extends into the flarne region ~ ', ro 94n83s4 ~ ~ '3 7 7 6 PCT/US94/06010 of a flame 58 sustained by metal bumer appar~tus 59, which is electrically referenced to ground 52. This circuit could also be irnplemented with a capacitor in place of resisto 56.
As illustrated by waveform E in Figure 5, drive generator 51 produces periodic 5 pulses of alternating current which are supplied through resistor 56, or through a corresponding capacitor, to flarne probe 57. With no flame present in the flame region, no electrical path to ground is provided through fl~rne probe 57 and burner apparatus 59. ln that event, the signal at the flame probe is centered about 0 volts, in accordance with the excitation signal produced by generator 51. However, if a flame is present in 10 the flame region, a shunt electrical path to ground 52 is provided through probe 57, flame 58 and burner apparatus S9 during positive excursions of the voltage supplied to probe 57. This has the effect of impressing a negative bias on the signal at the flarne probe, as illustrated by a portion of waveforrn F in Figure 5.
The signal at flarne probe 57 is supplied to a filter/amplifier 60 referenced tolS ground 52 in which the AC component of the signal is removed, leaving only a DC
: signal corresponding to the envelope of the AC signal when flame is present.
The circuit diagram of Figure 6 provides a more detailed representation of the flame sensor of Figure 4. The sarne reference numerals are used to designate cornrnon elements in both Figures.
~1: 20 As illustrated in Figure 6, electrical power for the sensor is provided through a step down transformer 62 whose primary winding may be connected to a suitable altcnlating current source, such as provided by an electrical utility, through a pair of taminals 63. A secondary winding of transformer 62 is cormected between ground 52 ~d, tbrough a resistor 64r to a simple half wave rectifier and filter circuit formed by a 2S diode 65 and a capacitor 66. This primary power supply may, for example, be designed to produce approximatély 34 volts DC which, for purposes of control electror~ics to be descdbed hereinafter, may be further reduced to five volts DC by a low voltage power supply comprising a Zener regulator 67 having a filter capacitor 68 connected in parallel ~erewith in series with a resistor 69.
Switchable AC ~rive generator 51 is cormected to be energized from the pIimary DC power supply throug}l conductor 70. Generator 51 comprises a DC to AC converter desigmcd to opcrate at 30 KHz, amd to gencrate an output of approximately 200 volts ~0 94/28354 PCT/US94/06010 3i~31~ 6 -8-AC. The generator is based on a Colpitts oscillator design comprising an NPN
transistor 72 whose collector is connected to power supply conductor 70 through a primary transforrner winding 73, and whose emitter is connected to ground 52 through a resistor 74. A pair of series connected capacitors 75 and 76 are connected across 5 winding 73. The oscillator operates in a common base configuration, with positive ~eedback from the collector of transistor 72 to the emitter thereof through a voltage divider formed by capacitors 75 and 76. A bypass capacitor 77 between power supply conductor 70 and ground 52 prevents undesirable modes of operation which may occur when power supply impedances interact with the oscillator. The base electrode ofo transistor 72 is supplied with a square wave signal as will hereinafter be described through a resistor 78.
The series equivalent capacitance of capacitors 75 and 76, together with the inductance of primary winding 73, form a tank circuit of the oscillator, and establish the operating frequency. A secondary winding 80 of the transformer is connected through a capacitor 81 between probe 57 and ground 52. A suitable turns ratio of windings 73 and 80 provides the desired secondary winding voltage, which is applied to probe 57.A positive enable signal from control electronics 55 supplied to the base of transistor 72 through resistor 78 establishes emitter current and puts translstor 72 into an active state, pom~it~ng oscillation stanup. The DC emitter voltage also serves as a 20 wltage clamp across capacitor 75, limiting oscillation amplitude at higher values of DC
input voltage. This limits transistor power, and eliminates the need for heat sinking.
Due to tbe high frequency of the excitation supplied to probe 57, only a single pole low pass filter is required. This filter is formed by a resistor 82 and a capacitor 83 connected in series between probe 57 and ground 52. A resistor 84 connected across 2S capacitor 83 drains the charge off the capacitor in the absence of a flame signal. A
Zener diode 85 also connected across capacitor 83, limits the voltage thereacross to allow the charge to be quickly drained offthe capacitor.
l~e sig~al at the junction of resistor 82 and capacitor 83 is supplied to ~e gate electrode of a FET 87"-whose drain electrode is supplied with voltage from the low 30 voltage power supply through a resistor 88, and whose source electrode is connected to ~ound 52. The output signal of filter/amplifier 60 is taken from the drain electrode of transistor 87. This signal folms an input signal to control electronics 55, which may be ~-' ``. `.~0 94/283~4 . ~J ~ PCT/US94/06010 .~ ; .
. ~; . . g . ;, implemented with a microprocessor to perform a variety of functions, including supplying a square wave control signal to drive generator 51. A flow diagrarn of the operation by which the signal is generated is provided in Figure 7.
In particular, as shown in Figure 7, upon energization of the primary power . . 5 supply, the output signal of control electronics 55 goes high. Thiereafter, there is a .05 second delay, after which the control electronics deterrnines whether filter/amplifier 60 is producing an output corresponding to a flame. This output is read and decoded to provide a flame indication.
After another .05 second delay, control electronics 55 provides a low eontrol ~10 signal to drive generator 51, thereby tenninating its supply of excitation to probe 57.
After another .05 second delay, control electronics 55 reads the output signal of filter/amplifier 60. If the filter/arnplifier output signal corresponds to presence of a flame, control electronics $5 determines that the flame signal~ is erroneous, and that a critical component in filter/amplifier 60 has failed.
With roference to Figure 5, waveforrn G illustrates the output of filter/amplifier 60 in proper operation. Waveforms G' and G" illustrate the outputs of filter/arnplifier 60 if resistor 84 fails open and if transistor 87 fails open, respectively. In particular, if resistor 84 fails open, the charge on capacitor 83 is not bled off during thie intervals between generation of successive pulses of alternating current, leaving a low voltage on the gate of transistor 87, and producing a continuously high output from filter/amplifier 60. Likewise, if transistor 87 fails open, the output of filter/amplifier 60 remains high regardless of actual flame status. Thus, the output signal of filter/amplifier 60 is very different if there is a failed component than for any valid flame signal.
The foregoing technique may be used to reduce the number of critical 2S components required to construct a fail-safe flame detection circuit since redundant components are not required. Ln addition, critical component failure is detected~ ~ i~i~ , In accordance with the foregoing description, the applicants have provided a unique fail-safe flame de ection circuit which does not rely on redundant components.
Although a particular embodiment has been shown~and described in detail for a illus~ative purposes, coverage is not to be limited by the disclosed embodiment, but only by the terms of the following claims.
BACKGROUND OF THE INVENTION
The present invention relates generally to flame detectors and detection methodsbased on electric current rectification properties of a flame, and, more specifically, to 5 such a detector and detection method employing periodic pulses of alternating current excitation in a manner to permit detection of inoperable electrical components which could result in flame detection errors.
Combustion systems, such as those used in furnaces, boilers and other appliances in which controlled burning takes place, commonly utilize automatic control 0 systems to ignite, control the flow of, and monitor the combustion of a fuel, such as natural gas, oil, etc. One of the required functions for such an automatic control system .
is to monitor the flame, and, in its absence, terminate the flow of the fuel to avoid serious hazards. Thus, it is essential that any flame detection apparatus in such a system be designed and constructed to operate in a highly reliable manner.
IS One well known technique for detecting the presence of a flame is based on electrical properties associated with the fla ne. As a flame burns, it produces an ioniæd region in its vicinity, thereby providing an electrically conductive medium. This property can be utiliæd in conjunction with a probo placed into the flame, and agrounded metal burner to produce a usable electrical signaL If such apparatus is-~ 20 conslruc~d with an effective grounded burner area greater than the effective probe area, typically in at least a 4 to 1 ratio, the flame will exhibit electrical characteristics som what similar to those of a diode in series with a 10 megobm resistor. If an ; alt~nabng current signal is injected into the flame by the probe, the signal will be rcbfied by the flame. Appropriate filtering and amplification circuitry may then be 2S employed to extract the rectified sig~al.
~ Two practical applications of this technique are illustrated in Figures 1 and 3, ; which are schematic diagrams of previously known systems. Figure 1 illustrates a shunt topology implementation in which an alternating current drive generator is connected dectrically in parallel with the burnerMa ne/probe system. If a flame is present, a 30 voltage divider will be formed during the positive excursions of the AC drive signal.
- This will have the effect of developing a negative bias on the AC signal at the input of a : :
WO 94/28354 C~ 3~ 7 ~J PCT/US94/06010 --flame filter/amplifier generally designed to remove the AC component, leaving only a DC signal indicative of the presence or absence of a flame.
Figure 3 illustrates a series topology implementation of the prior flame rectification detection technique. The requirements for the detector system components s are generally the same as for those in the shunt topology implementation, excepl that current, rather than voltage, signals are processed.
Because the circuitry for performing the filtering and amp}ifying is considered safety related, industry standards require that first and second level failure modes must not compromise its function. This requirement has led to the use of redundant circuit o elements, adding expense, leakage paths and crowded circuit board conditions. Thus, a need exists for a flame detector design which provides fail safe operation without ~ 1 requiring redundant components.
i SI~MMARY OF THE INVENTION
The invention is a flame sensing system and method based on electric current 5 rectification properties of a flame, the system and method utilizing pulsed alternating current excitation in a manner to avoid flame indication errors resulting from electrical component failures, without requiring redundant components. The system includes a drive generator for exciting a pair of electrodes in a fla ne region with periodic pulses of altemating current which are imparted with an electrical bias if a flarne is present. A
20 filter/amplifier attenuates the AC component of current between the electrodes, leaving a DC signal corresponding to presence or absence of a flame. Output logic ;s operable to indicate presence of a flame only if the DC signal corresponds to presence of flame during the time the electrodes are being excited with a pulse of alternating current, and does not correspond to presence of a flame during ~e time between excitation with 25 successive pulses of alternating current. A DC signal corresponding to presence of a flame during the time between excitation of the electrodes with successive pulses of alternating cu~rent indicates failure of a system component, thenby permitting fail safe operation.
A specific objective of the invention is to provide a flame detector design which 30 requires a minimurn number of components in the sensitive, high impedance portion of the filter/amplifier circuitry.
~fr.. . ~
WO 94/28354 . ~ 7 7 ~ PCT/US94/06010 A further objective is to provide a desi'gn which allows reliable detection of loss of flame in a substantially shorter time than the current industry standard of 0.8 seconds.
Yet, a fi~rther objective is to provide a design which permits detection of failure of critical components in the filter/amplifier circuitry substantially any time during its s operation, and not just at the beginning of a flame cycle.
ps~IEF DESCRIPTION OF THE DRAWlNGS ' ' Figure 1 is a schematic diagram of a prior art rectification type flarne sensor employing a shunt circuit topology design.
Figure 2 is a representation of signal waveforms at indicated points in the sensor 0 of Figure 1.
Figure 3 is a block diagram of a prior art rectification type flame sensor employing a series circuit topology design.
Figure 4 is a block diagram of a rectification type flame sensor in accordance 'with the applicants' invention.
IS Figure 5 is a representation of signal waveforms at various points in the system of Figure 4, and showing the normal system output, as well as system outputs when cc~in component failures exist.
Figure 6 is a circuit diagram of the flame sensor of Figure 4.
~ Figure 7 is a flow diagram of certain logic operations accomplished in a portion - ~ 20 of the circuit of Fig~ure 6.
- ~ P,SCRIPTION OF THE PREFF,RRED EMBODIMENT
- ~ Refernng to Figure 1, réference numeral 10 generally identifies a shunt topology form of a prior art flame sensing system based on the electric current rectification cbar~cteristics of a flame. System 10 is shown as including an alternating current drive 2S generator 11 in series with a resistor 13 connected across a burner apparatus having a flame sensing electrode. Both generator 11 and the burner apparatus are electrically ferenced to ground 12.
~' With particular Kference to the burner system, metal burner apparatus 14 is clectrically connected to ground 12, ~e burner apparatus being adapted to support a ~30 flamc 15 in a flame region. A flame probe 16, which extends into the flame region, is connected to generator 11 ~rough resistor 13 so as to be excited by the altemating current produced by the generator Burner apparatus 14 conventionally is constructed to ., ~WO 94/283.~4 PCT/US94/06010 2133~ 4 .3 have a effective grounded area of at least four times the effective area of probe 16, thereby, in conjunction with flame 15, effectively forming an electrical rectifier. As shown in dashed line symbols in parallel with burner 14 and probe 16, the burnerMame/probe arrangement electrically roughly appears as a resistor 17 in series .~ 5 with a diode 18, the resistor having a high resistance value, typically on the order of 10 megohms.
A node 19 between resistor 13 and probe 16 is connected to a filter/amplifier 20.
Filter/amplifier 20 includes a first resistor 21 between node 19 and a node 22, which is connected to the gate electrode of a field effect transistor (FET) 23.
loAs shown in Figure 1, three resistors, identified by reference nurnerals 24, 25 and 26, and a capacitor 27 are connected in parallel between node 22 and ground 12.
FET 23 is connected through its source and drain electrodes in series with a resistor 28 between a positive voltage supply terminal 30 and ground 12. The output signal of filterlamplifier 20 is produced at a temlinal 31 cormected between FET 23 and resistor 15 28.
In operation, the burnerMame/probe system imparts a negative bias to the AC
excitation signal. Resistor 21 and capacitor 27 form a low-pass filter which extracts the DC component from ~e rectified excitation signal. FET 23 detects the DC level at the - output of the fi1ter. In particular, FET 23 becomes nonconducting when the signal at 20 node 22 corresponds to presence of a flame.
A bleed resistor in parallel with capacitor 27 is required to drain off the charge on the capacitor when the flame is lost. This is a critical function, since the automatic control system must act to shut off the flow of fuel in the absence of a flame to avoid a ha~dous situation. Therefore, redundant resistors 24, 25 and 26 are provided so ~at, 25 in the absence of flame, the charge on capacitor 27 will drain off, even if two of these resistors fail in an open circuit condition.
The foregoing requirement adds cost and complexity to the circuit. Further, because the flame presents a high impedance, extraordinary techniques must be used in the filtering and amplifying circuitry. In particular, the impedances of the filter 30 elements must also be in the 50 megohm range to avoid excessive loading of the 10 megohm impedance of the flame. The redundant components add potentially problematic leakage paths, thereby compromising circuit reliably, and limiting its use.
-~ WO 94/283S4 ~ 1 r! .3 7 7 ~ PCTIUS94/06010 .~ .
The wavefo~ns which occur at designàted points in the flame sensor of Figure 1 during its operation are illustrated in Figure 2, in which the top waveform indicates a short interval during which flame 15 is present. The second waveform illustrates a relatively high frequency AC signal produced by drive generator 11, which is present at 5 point A in the sensor of Figure 1. The third waveform in Figure 2 shows that during the interval when flame 15 is present, the excitation signal is rectified to produce at point B
a voltage having attenuated positive values. This signal forms the input to .~
filter/amplifier 20 which removes the AC component, as has been described, to provide . 1 at point C a signa~ as illustrated by the bottom waveform in Figure 2. This signal is lo indicative of presence or absence of a flame.
In the prior art series topology implementation of Figure 3, various elements corresponding to those in Figure 1 are realranged such that drive generator 11' is connected in series between probe 16' and filterlamplifier 20'. This series combination is, in turn, effectively connected in series with burner 14' and flame 15' between ground 15 12' and output terminal 31'.
By way of context and background for the applicants' invention, two of the design requirements for the control system under consideration were that it be polarity insensitive, and that it operate in the presence of condensed moisture. These requirements particularly impact the flame sensor circuitry. When water condenses on 20 higb impedance filter/amplifier components, leakage paths are created physically across the bodies of the components and between the various electrical nodes. These leakage patbs can completely attenuate the flame signal. This situation can be improved by (1) reducing the nurnber of components across which leakage paths can occur, (2) msximizulg physical separation of the components, both lead to lead and node to node, 2S and (3) driving the filter/amplifier with as large a signal as possible.
For tbe particular application for which the disclosed implementation was designed, a transformer based voltage step up circuit is employed to provide polarity insensitivity. However, it is pointed out tbat the inventive concept is useful in applications not requirhg polarity insensitivity, and that polarity insensitivity can be 30 provided by means otber than a transformer based step up circuit.
By designing the disclosed step up circuit to produce as high a frequency as possible, the cost of magnetic components is minimized~ along with the number of poles ¦ wo 94/28354 ~ PCT/US94/06010 required in the filter/amplifier. Minimizing the number of filter poles also minimizes the number of high impedance nodes and components, and allows the remaining components to be spread out as much as possible within the packaging constraints.
The upper frequenc~ limit is determined by the stray capacitance to ground of 5 the flame detection probe system and of the flame itself. This capacitance, when ,:
combined with the series impedance of the flame sensor power supply, forrns a first order low pass filter. Experimental results indicate that 40 KHz is the upper limit. 30 KHz is a practical compromise between design margin and magnetic component costs.
An additional advantage of the high operating frequency is that it reduces the lo sensor response time to loss of flame. It also perrnits use of a single pole filter having a short decay response time. The short decay time allows a design approach which eliminates the need for the FMEA-required triple parallel high resistance resistors otherwise required for reliability in draining offthe charge from the filter capacitor. In particular, control electronics, which will be described in greater detail hereinafter, turns lS the high frequency, high voltage flame probe excitation signal on and off at a 5 Hz rate.
In the presence of a flarne, the control electronics processor will see a similar S Hz signal at the output of the flarne amplifier. If the single bleed resistor opens, the capacitor will remain charged and the control electronics will deterrnine that the flarne probe detection signal no longer matches the flame probe drive signal. Such operation 20 may also be used to detect a number of other component ~ailures.
Turning to Figure 4, reference numeral 50 generally identifies a shunt topology version of a flame sensor in accordance with the applicants' invention. System 50 includes an alternating current drive generator 51 referenced to an electrical ground 52, and operable to produce an alternating current excitation signal on an output conductor 25 53. Generation of the excitation signal is controlled by a signal on a control conductor 54 provided by co~trol electronics 55. As will be described hereinafter, the control electronics are designed to produce a square wave, shown as waveform D in Figure 5, having a predeterminéd repetition rate. As previously indicated, repetition rate of five r~tions per second,~for the control signal, and a frequency of 30 KHz for the 30 alten~ating curTent excitation signal, have been found suitable for the sensor of Figure 4.
In the disclosed implementation, the excitation signal on conductor 53 is supplied through a resistor 56 to a flame probe 57 which extends into the flarne region ~ ', ro 94n83s4 ~ ~ '3 7 7 6 PCT/US94/06010 of a flame 58 sustained by metal bumer appar~tus 59, which is electrically referenced to ground 52. This circuit could also be irnplemented with a capacitor in place of resisto 56.
As illustrated by waveform E in Figure 5, drive generator 51 produces periodic 5 pulses of alternating current which are supplied through resistor 56, or through a corresponding capacitor, to flarne probe 57. With no flame present in the flame region, no electrical path to ground is provided through fl~rne probe 57 and burner apparatus 59. ln that event, the signal at the flame probe is centered about 0 volts, in accordance with the excitation signal produced by generator 51. However, if a flame is present in 10 the flame region, a shunt electrical path to ground 52 is provided through probe 57, flame 58 and burner apparatus S9 during positive excursions of the voltage supplied to probe 57. This has the effect of impressing a negative bias on the signal at the flarne probe, as illustrated by a portion of waveforrn F in Figure 5.
The signal at flarne probe 57 is supplied to a filter/amplifier 60 referenced tolS ground 52 in which the AC component of the signal is removed, leaving only a DC
: signal corresponding to the envelope of the AC signal when flame is present.
The circuit diagram of Figure 6 provides a more detailed representation of the flame sensor of Figure 4. The sarne reference numerals are used to designate cornrnon elements in both Figures.
~1: 20 As illustrated in Figure 6, electrical power for the sensor is provided through a step down transformer 62 whose primary winding may be connected to a suitable altcnlating current source, such as provided by an electrical utility, through a pair of taminals 63. A secondary winding of transformer 62 is cormected between ground 52 ~d, tbrough a resistor 64r to a simple half wave rectifier and filter circuit formed by a 2S diode 65 and a capacitor 66. This primary power supply may, for example, be designed to produce approximatély 34 volts DC which, for purposes of control electror~ics to be descdbed hereinafter, may be further reduced to five volts DC by a low voltage power supply comprising a Zener regulator 67 having a filter capacitor 68 connected in parallel ~erewith in series with a resistor 69.
Switchable AC ~rive generator 51 is cormected to be energized from the pIimary DC power supply throug}l conductor 70. Generator 51 comprises a DC to AC converter desigmcd to opcrate at 30 KHz, amd to gencrate an output of approximately 200 volts ~0 94/28354 PCT/US94/06010 3i~31~ 6 -8-AC. The generator is based on a Colpitts oscillator design comprising an NPN
transistor 72 whose collector is connected to power supply conductor 70 through a primary transforrner winding 73, and whose emitter is connected to ground 52 through a resistor 74. A pair of series connected capacitors 75 and 76 are connected across 5 winding 73. The oscillator operates in a common base configuration, with positive ~eedback from the collector of transistor 72 to the emitter thereof through a voltage divider formed by capacitors 75 and 76. A bypass capacitor 77 between power supply conductor 70 and ground 52 prevents undesirable modes of operation which may occur when power supply impedances interact with the oscillator. The base electrode ofo transistor 72 is supplied with a square wave signal as will hereinafter be described through a resistor 78.
The series equivalent capacitance of capacitors 75 and 76, together with the inductance of primary winding 73, form a tank circuit of the oscillator, and establish the operating frequency. A secondary winding 80 of the transformer is connected through a capacitor 81 between probe 57 and ground 52. A suitable turns ratio of windings 73 and 80 provides the desired secondary winding voltage, which is applied to probe 57.A positive enable signal from control electronics 55 supplied to the base of transistor 72 through resistor 78 establishes emitter current and puts translstor 72 into an active state, pom~it~ng oscillation stanup. The DC emitter voltage also serves as a 20 wltage clamp across capacitor 75, limiting oscillation amplitude at higher values of DC
input voltage. This limits transistor power, and eliminates the need for heat sinking.
Due to tbe high frequency of the excitation supplied to probe 57, only a single pole low pass filter is required. This filter is formed by a resistor 82 and a capacitor 83 connected in series between probe 57 and ground 52. A resistor 84 connected across 2S capacitor 83 drains the charge off the capacitor in the absence of a flame signal. A
Zener diode 85 also connected across capacitor 83, limits the voltage thereacross to allow the charge to be quickly drained offthe capacitor.
l~e sig~al at the junction of resistor 82 and capacitor 83 is supplied to ~e gate electrode of a FET 87"-whose drain electrode is supplied with voltage from the low 30 voltage power supply through a resistor 88, and whose source electrode is connected to ~ound 52. The output signal of filter/amplifier 60 is taken from the drain electrode of transistor 87. This signal folms an input signal to control electronics 55, which may be ~-' ``. `.~0 94/283~4 . ~J ~ PCT/US94/06010 .~ ; .
. ~; . . g . ;, implemented with a microprocessor to perform a variety of functions, including supplying a square wave control signal to drive generator 51. A flow diagrarn of the operation by which the signal is generated is provided in Figure 7.
In particular, as shown in Figure 7, upon energization of the primary power . . 5 supply, the output signal of control electronics 55 goes high. Thiereafter, there is a .05 second delay, after which the control electronics deterrnines whether filter/amplifier 60 is producing an output corresponding to a flame. This output is read and decoded to provide a flame indication.
After another .05 second delay, control electronics 55 provides a low eontrol ~10 signal to drive generator 51, thereby tenninating its supply of excitation to probe 57.
After another .05 second delay, control electronics 55 reads the output signal of filter/amplifier 60. If the filter/arnplifier output signal corresponds to presence of a flame, control electronics $5 determines that the flame signal~ is erroneous, and that a critical component in filter/amplifier 60 has failed.
With roference to Figure 5, waveforrn G illustrates the output of filter/amplifier 60 in proper operation. Waveforms G' and G" illustrate the outputs of filter/arnplifier 60 if resistor 84 fails open and if transistor 87 fails open, respectively. In particular, if resistor 84 fails open, the charge on capacitor 83 is not bled off during thie intervals between generation of successive pulses of alternating current, leaving a low voltage on the gate of transistor 87, and producing a continuously high output from filter/amplifier 60. Likewise, if transistor 87 fails open, the output of filter/amplifier 60 remains high regardless of actual flame status. Thus, the output signal of filter/amplifier 60 is very different if there is a failed component than for any valid flame signal.
The foregoing technique may be used to reduce the number of critical 2S components required to construct a fail-safe flame detection circuit since redundant components are not required. Ln addition, critical component failure is detected~ ~ i~i~ , In accordance with the foregoing description, the applicants have provided a unique fail-safe flame de ection circuit which does not rely on redundant components.
Although a particular embodiment has been shown~and described in detail for a illus~ative purposes, coverage is not to be limited by the disclosed embodiment, but only by the terms of the following claims.
Claims (12)
1. Flame detection apparatus comprising:
a burner 59 for sustaining flame 58 in a flame region;
a reference electrode 59 proximate the flame region;
an injector electrode 57 positioned to transmit electric current through the flame region to said reference electrode 59, said injector electrode 57 having an effective area smaller than the effective area of said reference electrode 59, whereby electric current rectification is effectively achieved by said reference and injector electrodes 59 & 57 and flame 58 in the flame region;
a signal generator 51 for producing alternating voltage having a predetermined envelope;
connecting means 52, 53, 56 for electrically connecting said signal generator 51between said reference and injector electrodes 59 & 57 to supply the alternating voltage therebetween, whereby, when flame 58 is present in the flame region, a signal having a substantially unipolar bias corresponding to the envelope is produced; and detector means 60, 55 connected to said injector electrode 57, said detector means 60, 55 being responsive to a signal having a substantially unipolar bias corresponding to the envelope, and operable in response to such a signal to indicate presence of a flame 58.
a burner 59 for sustaining flame 58 in a flame region;
a reference electrode 59 proximate the flame region;
an injector electrode 57 positioned to transmit electric current through the flame region to said reference electrode 59, said injector electrode 57 having an effective area smaller than the effective area of said reference electrode 59, whereby electric current rectification is effectively achieved by said reference and injector electrodes 59 & 57 and flame 58 in the flame region;
a signal generator 51 for producing alternating voltage having a predetermined envelope;
connecting means 52, 53, 56 for electrically connecting said signal generator 51between said reference and injector electrodes 59 & 57 to supply the alternating voltage therebetween, whereby, when flame 58 is present in the flame region, a signal having a substantially unipolar bias corresponding to the envelope is produced; and detector means 60, 55 connected to said injector electrode 57, said detector means 60, 55 being responsive to a signal having a substantially unipolar bias corresponding to the envelope, and operable in response to such a signal to indicate presence of a flame 58.
2. The flame detection apparatus of claim 1 wherein:
said signal generator 51 is operable to produce periodic intervals of alternating voltage, the periodic intervals having a predetermined repetition rate; and said detector means 60, 55 is responsive to periodic intervals of alternating signal having a substantially unipolar bias and the predetermined repetition rate.
said signal generator 51 is operable to produce periodic intervals of alternating voltage, the periodic intervals having a predetermined repetition rate; and said detector means 60, 55 is responsive to periodic intervals of alternating signal having a substantially unipolar bias and the predetermined repetition rate.
3. The flame detector apparatus of claim 2 wherein said detector means 60, 55 includes output means operable to indicate failure of a component within said detector means 60, 55 if an alternating signal having a substantially unipolar bias is produced during the time between production of successive intervals of alternating voltage by said signal generator 51.
4. The flame sensing apparatus of claim 3 wherein said output means is operable to indicate presence of a flame only if an alternating signal having a substantially unipolar bias is produced during the time said signal generator 51 is producing an interval of alternating voltage, and an alternating signal having a substantially unipolar bias is not produced during the time between production of successive intervals of alternating voltage by said signal generator 51.
5. In flame sensing apparatus of the type including a signal generator 51 for impressing an alternating electrical signal between reference and injector electrodes 59 & 57 adapted to cause electric current to flow through flame 58 in a flame region, whereby the signal is rectified when a flame 58 is present, the rectified signal being conditioned by a filter 82, 83, 84 including a capacitor 83 having a bleed resistor 84 thereacross, the voltage on the capacitor 83 being used to control amplifier 87 apparatus whose output is indicative of presence or absence of a flame 58, improved means for detecting failure of critical components, including the capacitor, bleed resistor and amplifier 87 device, in the filter 82, 83, 84 and amplifier 87 apparatus, comprising:
signal generator means 51 for supplying to the injector electrode 57 a pulse of alternating voltage; and logic means 55 connected to receive the amplifier 87 apparatus output, and operable to indicate failure of an electrical component in the filter 82, 83, 84 or amplifier 87 apparatus if the amplifier 87 apparatus output indicates presence of a flame at any time except during the time a pulse of alternating voltage is being supplied by said signal generator means 51.
signal generator means 51 for supplying to the injector electrode 57 a pulse of alternating voltage; and logic means 55 connected to receive the amplifier 87 apparatus output, and operable to indicate failure of an electrical component in the filter 82, 83, 84 or amplifier 87 apparatus if the amplifier 87 apparatus output indicates presence of a flame at any time except during the time a pulse of alternating voltage is being supplied by said signal generator means 51.
6. The flame sensing apparatus of claim 5 wherein said signal generator means 51is operable to supply periodic pulses of alternating voltage, the pulses having a predetermined repetition rate.
7. The flame sensing apparatus of claim 6 wherein said logic means 55 is operable to indicate presence of a flame only if the amplifier 87 apparatus output indicates presence of a flame during the time a pulse of alternating voltage is being supplied by said signal generator means 55, and the amplifier 87 apparatus output does not indicate presence of a flame during the time between supply of successive pulses of alternating voltage by said signal generator means 55.
8. In flame detection apparatus of the type including a generator 51 for supplying an alternating voltage signal to first and second electrodes 57 & 59 adapted to produce substantially unidirectional electric current flow therebetween through an ionization region associated with a flame 58, and a detector 60, 55 for producing a flame indicating output in response to presence of substantially unidirectional electric current flow between the first and second electrodes 57 & 59, the improvement which comprises:
a generator 51 adapted to produce an alternating voltage in packets having a predetermined envelope, the packets being produced at a predetermined repetition rate;
a filter 82, 83 for receiving the voltage between the first and second electrodes 57 & 59, said filter 82, 83 being formed of electrical components which, if functioning properly, produce a biased voltage signal corresponding to the envelope of the alternating voltage produced by said generator 51; and an amplifier 87 responsive to the biased voltage signal produced by said filter 82, 83 to produce an output uniquely corresponding to the envelope of the alternating voltage produced by said generator 51 only if the biased voltage signal corresponds to the envelope of the alternating voltage.
a generator 51 adapted to produce an alternating voltage in packets having a predetermined envelope, the packets being produced at a predetermined repetition rate;
a filter 82, 83 for receiving the voltage between the first and second electrodes 57 & 59, said filter 82, 83 being formed of electrical components which, if functioning properly, produce a biased voltage signal corresponding to the envelope of the alternating voltage produced by said generator 51; and an amplifier 87 responsive to the biased voltage signal produced by said filter 82, 83 to produce an output uniquely corresponding to the envelope of the alternating voltage produced by said generator 51 only if the biased voltage signal corresponds to the envelope of the alternating voltage.
9. The flame detection apparatus of claim 8 wherein:
said generator 51 is operable to produce periodic pulses of alternating voltage;and the biased voltage signal is produced by said filter 82, 83 only during the timesaid generator 51 is producing a pulse of alternating voltage.
said generator 51 is operable to produce periodic pulses of alternating voltage;and the biased voltage signal is produced by said filter 82, 83 only during the timesaid generator 51 is producing a pulse of alternating voltage.
10. The flame detection apparatus of claim 9 wherein the frequency of the alternating voltage produced by said generator 51 is greater than the repetition rate of the packets said alternating voltage.
11. A method of reliably detecting flame by means of a flame sensor whose operation is based on electrical rectification characteristics of a flame, the flame sensor including a signal filter 82, 83 and amplifier 87 containing critical electrical components subject to failure which could result in an erroneous indication of presence or absence of a flame, the method of comprising the steps of:
supplying an input signal characterized by separated pulses of alternating voltage having a predetermined frequency to an electrode 57 adapted to inject the input signal into a flame region 58;
conditioning the voltage present at the injector electrode 57 by means of a filter 82, 83 which, in normal operation, substantially attenuates signal frequencies at the predetermined frequency to produce a voltage waveform corresponding to the pulseenvelope of the input signal, the voltage waveform having a substantially non-zero value only when a flame 58 is present and a pulse of alternating voltage is being supplied;
producing a preliminary flame detection signal during presence of a voltage waveform having a substantially non-zero value; and producing an indication of critical electrical component failure in the event the preliminary flame detection signal indicates presence of a flame during the time between supply of successive pulses of alternating voltage.
supplying an input signal characterized by separated pulses of alternating voltage having a predetermined frequency to an electrode 57 adapted to inject the input signal into a flame region 58;
conditioning the voltage present at the injector electrode 57 by means of a filter 82, 83 which, in normal operation, substantially attenuates signal frequencies at the predetermined frequency to produce a voltage waveform corresponding to the pulseenvelope of the input signal, the voltage waveform having a substantially non-zero value only when a flame 58 is present and a pulse of alternating voltage is being supplied;
producing a preliminary flame detection signal during presence of a voltage waveform having a substantially non-zero value; and producing an indication of critical electrical component failure in the event the preliminary flame detection signal indicates presence of a flame during the time between supply of successive pulses of alternating voltage.
12. The method of claim 11, including the further step of producing a final flame indication signal only if the preliminary flame indication signal indicates presence of a flame during the time a pulse of alternating voltage is being supplied, and if the preliminary flame indication signal does not indicate presence of a flame during the time between successive pulses of alternating voltage.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US6882593A | 1993-05-28 | 1993-05-28 | |
| US08/068,825 | 1993-05-28 | ||
| US08/099,667 US5472336A (en) | 1993-05-28 | 1993-07-29 | Flame rectification sensor employing pulsed excitation |
| US08/099,667 | 1993-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2135776A1 true CA2135776A1 (en) | 1994-12-08 |
Family
ID=26749423
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002135776A Abandoned CA2135776A1 (en) | 1993-05-28 | 1994-05-27 | Flame rectification sensor employing pulsed excitation |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5472336A (en) |
| AU (1) | AU688772B2 (en) |
| CA (1) | CA2135776A1 (en) |
| WO (1) | WO1994028354A1 (en) |
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| US5722822A (en) * | 1995-05-03 | 1998-03-03 | Carrier Corporation | Flame sensor verification |
| EP0861402A1 (en) * | 1995-11-13 | 1998-09-02 | Gas Research Institute | Flame ionization control apparatus and method |
| US5704775A (en) * | 1996-03-28 | 1998-01-06 | Gilbert; Paul A. | Auxiliary igniter and control for a furnace |
| US6060719A (en) * | 1997-06-24 | 2000-05-09 | Gas Research Institute | Fail safe gas furnace optical flame sensor using a transconductance amplifier and low photodiode current |
| US5927963A (en) * | 1997-07-15 | 1999-07-27 | Gas Electronics, Inc. | Pilot assembly and control system |
| US6299433B1 (en) | 1999-11-05 | 2001-10-09 | Gas Research Institute | Burner control |
| GB2367172B (en) * | 2000-04-26 | 2004-02-18 | Pektron Group Ltd | Detection apparatus and a method of detection |
| ES2270940T3 (en) * | 2000-12-01 | 2007-04-16 | Vaillant Gmbh | GUARDALLAMAS CIRCUIT. |
| US6743010B2 (en) | 2002-02-19 | 2004-06-01 | Gas Electronics, Inc. | Relighter control system |
| US6985080B2 (en) * | 2003-03-07 | 2006-01-10 | Ranco Incorporated Of Delaware | Flame sense circuit and method with analog output |
| NL1024388C2 (en) * | 2003-09-26 | 2005-03-31 | Betronic Design B V | Flame monitoring system. |
| US7241135B2 (en) * | 2004-11-18 | 2007-07-10 | Honeywell International Inc. | Feedback control for modulating gas burner |
| US8310801B2 (en) * | 2005-05-12 | 2012-11-13 | Honeywell International, Inc. | Flame sensing voltage dependent on application |
| US7768410B2 (en) * | 2005-05-12 | 2010-08-03 | Honeywell International Inc. | Leakage detection and compensation system |
| US8066508B2 (en) | 2005-05-12 | 2011-11-29 | Honeywell International Inc. | Adaptive spark ignition and flame sensing signal generation system |
| US8085521B2 (en) * | 2007-07-03 | 2011-12-27 | Honeywell International Inc. | Flame rod drive signal generator and system |
| US7800508B2 (en) * | 2005-05-12 | 2010-09-21 | Honeywell International Inc. | Dynamic DC biasing and leakage compensation |
| US7764182B2 (en) * | 2005-05-12 | 2010-07-27 | Honeywell International Inc. | Flame sensing system |
| US8300381B2 (en) * | 2007-07-03 | 2012-10-30 | Honeywell International Inc. | Low cost high speed spark voltage and flame drive signal generator |
| US8875557B2 (en) | 2006-02-15 | 2014-11-04 | Honeywell International Inc. | Circuit diagnostics from flame sensing AC component |
| DE102007018122B4 (en) * | 2007-04-16 | 2013-10-17 | Viessmann Werke Gmbh & Co Kg | Flame monitoring device with a voltage generating and measuring arrangement and method for monitoring a burner by means of the flame monitoring device |
| US7944678B2 (en) * | 2008-09-11 | 2011-05-17 | Robertshaw Controls Company | Low voltage power supply for spark igniter and flame sense |
| US10132770B2 (en) * | 2009-05-15 | 2018-11-20 | A. O. Smith Corporation | Flame rod analysis system |
| US9546788B2 (en) * | 2012-06-07 | 2017-01-17 | Chentronics, Llc | Combined high energy igniter and flame detector |
| ITPD20120281A1 (en) * | 2012-09-27 | 2014-03-28 | Sit La Precisa S P A Con Socio Uni Co | METHOD FOR THE MONITORING AND CONTROL OF COMBUSTION IN COMBUSTIBLE GAS BURNERS AND COMBUSTION CONTROL SYSTEM OPERATING ACCORDING TO THIS METHOD |
| US9494320B2 (en) | 2013-01-11 | 2016-11-15 | Honeywell International Inc. | Method and system for starting an intermittent flame-powered pilot combustion system |
| US10208954B2 (en) | 2013-01-11 | 2019-02-19 | Ademco Inc. | Method and system for controlling an ignition sequence for an intermittent flame-powered pilot combustion system |
| WO2016043821A1 (en) | 2014-09-18 | 2016-03-24 | Illinois Tool Works Inc. | Device for the ignition/re-ignition of the flame for a gas burner, for example in a cooktop, and corresponding method |
| US10678204B2 (en) | 2014-09-30 | 2020-06-09 | Honeywell International Inc. | Universal analog cell for connecting the inputs and outputs of devices |
| US10402358B2 (en) | 2014-09-30 | 2019-09-03 | Honeywell International Inc. | Module auto addressing in platform bus |
| US10042375B2 (en) | 2014-09-30 | 2018-08-07 | Honeywell International Inc. | Universal opto-coupled voltage system |
| US10288286B2 (en) | 2014-09-30 | 2019-05-14 | Honeywell International Inc. | Modular flame amplifier system with remote sensing |
| US10890326B2 (en) * | 2016-10-31 | 2021-01-12 | Robertshaw Controls Company | Flame rectification circuit using operational amplifier |
| US10473329B2 (en) | 2017-12-22 | 2019-11-12 | Honeywell International Inc. | Flame sense circuit with variable bias |
| US11236930B2 (en) | 2018-05-01 | 2022-02-01 | Ademco Inc. | Method and system for controlling an intermittent pilot water heater system |
| US10935237B2 (en) | 2018-12-28 | 2021-03-02 | Honeywell International Inc. | Leakage detection in a flame sense circuit |
| DE102019119206A1 (en) * | 2019-07-16 | 2021-01-21 | Vaillant Gmbh | Method and device for adapting the sensitivity of a detector for monitoring a flame in a heating device |
| US11656000B2 (en) | 2019-08-14 | 2023-05-23 | Ademco Inc. | Burner control system |
| US11739982B2 (en) | 2019-08-14 | 2023-08-29 | Ademco Inc. | Control system for an intermittent pilot water heater |
| US11635232B2 (en) * | 2020-03-26 | 2023-04-25 | Johnson Controls Tyco IP Holdings LLP | HVAC system flame sensor |
| US11821628B1 (en) * | 2020-06-25 | 2023-11-21 | Christopher A. Wiklof | Ultra wideband combustion sensor and systems |
| DE102020126788A1 (en) * | 2020-10-13 | 2022-04-14 | Ebm-Papst Landshut Gmbh | Flame amplifier for flame monitoring and associated method |
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|---|---|---|---|---|
| US3576556A (en) * | 1969-05-16 | 1971-04-27 | Pyronics Inc | Flame detector |
| US3781161A (en) * | 1972-01-03 | 1973-12-25 | Combustion Eng | Control logic test circuit |
| US3987358A (en) * | 1972-01-26 | 1976-10-19 | The Walter Kidde & Company, Inc. | Condition detector circuit |
| US4243372A (en) * | 1979-02-05 | 1981-01-06 | Electronics Corporation Of America | Burner control system |
| US4295129A (en) * | 1979-05-07 | 1981-10-13 | Electronics Corporation Of America | System condition indicator |
| GB2087117B (en) * | 1980-11-06 | 1984-06-20 | British Gas Corp | Burner safety system |
| US4444551A (en) * | 1981-08-27 | 1984-04-24 | Emerson Electric Co. | Direct ignition gas burner control system |
| JPS6057124A (en) * | 1983-09-09 | 1985-04-02 | Matsushita Electric Ind Co Ltd | Combustion controller |
| NL8401173A (en) * | 1984-04-12 | 1985-11-01 | Philips Nv | FLAME PROTECTION CIRCUIT. |
| JPS60232422A (en) * | 1984-05-02 | 1985-11-19 | Matsushita Electric Ind Co Ltd | Flame electric current detecting apparatus |
| US4955806A (en) * | 1987-09-10 | 1990-09-11 | Hamilton Standard Controls, Inc. | Integrated furnace control having ignition switch diagnostics |
-
1993
- 1993-07-29 US US08/099,667 patent/US5472336A/en not_active Expired - Lifetime
-
1994
- 1994-05-27 AU AU70474/94A patent/AU688772B2/en not_active Ceased
- 1994-05-27 WO PCT/US1994/006010 patent/WO1994028354A1/en active Application Filing
- 1994-05-27 CA CA002135776A patent/CA2135776A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1994028354A1 (en) | 1994-12-08 |
| AU688772B2 (en) | 1998-03-19 |
| US5472336A (en) | 1995-12-05 |
| AU7047494A (en) | 1994-12-20 |
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