DE2451449A1 - DYNAMIC INFRARED FLAME DETECTOR - Google Patents

Description

2A5H49

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6 Franhiuui a. M. 1
Pcaküiraße 13

8025

FORNEY INTERNATIONAL, INC., Carrollton, Texas, VStA

Dynamic infrared flame detector

The invention relates to a dynamic infrared flame detector for monitoring fossil fuel fired combustion systems and for controlling display devices and controlling the inflow of Fuel to selected burners in accordance with the flame condition. In the event of a flame failure it is For example, you may want to indicate this failure, set off an alarm, and start fueling as soon as possible possible to prevent in order to avoid flooding and a possible explosion in the combustion system.

The invention is applicable to both coal and oil fired Firing systems applicable and feeds in conjunction with burners that are fired with powdered coal special advantages. Gas-fired firing systems with oil-fired Ignition devices also represent a particularly advantageous field of application of the invention. This

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is due to the fact that an infrared detector is placed between an oil-fired pilot flame and a gas-fired Can differentiate between combustion flamesWith coal-fired burners, the infrared detector is able to can be seen through the coal dust and smoke surrounding the combustion zone · Ultra-violet flame detectors are also included not able and are therefore with the demand connected that the flame observation as close as possible the flame is made.

According to the invention is for fuel-fired Combustion systems created a dynamic infrared detector, in which the sampled signal with a small transistorized preamplifier circuit is amplified and then for further processing to a remotely located Solid-state main amplifier circuit is transmitted. The main amplifier circuit is in a signal receiver connection unit housed by the preamplifier circuit housed in a signal generator unit or a detector head is located remotely · The circuits of the two units are shielded via a two-wire Cable connected to each other, which can have a considerable length · The signaling unit is relatively compact and has a small optical attachment or nipple that fits into an opening is fitted in the ¥ and the combustion system and aligned with the flame to be observed

The small solid-state preamplifier circuit used to amplify the sampled infrared signal contains a Infrared sensor cell aimed at the combustion zone of the flame to be monitored. This is the whole Arrangement made in such a way that the nipple of the detector head or the signal transmitter unit is not in the interior of the combustion system As a result,

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there is no risk of the cell being exposed to heat and sparks will be damaged. Despite the distance of the cell from the combustion zone, the opposite is infrared radiation sensitive cell is able to determine the state of the flame as it passes through the area surrounding the combustion zone Can see smoke and dust atmospheres · The infrared sensor forms the flame fluctuations occurring in the observed combustion zone into one of the fluctuations corresponding electrical signal in order to be transmitted through the long shielded cable to the Main amplifier circuit in the remote signal receiver terminal unit from the transistor circuit in the signal transmitter unit is pre-amplified.

The main amplifier circuit receives the signal fluctuations from the infrared sensor circuit and further amplifies the fluctuations. The main amplifier circuit contains a filter part that adjusts to an optimal frequency range of 40 to 60 Hz in the light source frequency appeals to. It should be noted that the primary combustion zone is very rich in these frequencies is. The background frequencies fall outside this range. The frequency characteristic in dB of the output signal and in Hz the light source frequency increases gradually between 9 and 75 Hz to a maximum of +2 dB 75 Hz, where the level of the output signal, at 50 Hz is chosen equal to 0 dB, and then falls with increasing Hertz values of the light source frequency slowly decrease. on in this way, undesirable noise components are avoided. The main amplifier circuit takes in connection with an integrated control circuit, amplification and digital processing of the amplified signal fluctuations in front of the fuel flow to the monitored burner to control. A flame safety and alarm device can be used for this, for example a Alarm transmitter activated and fuel flow to the burner

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automatically turns off when the flame is suitable for a The delay time disappears.

The method of operation of the flame detector arrangement designed according to the invention is briefly described below. When the variable infrared radiation falls on the photosensitive cell from the combustion or ignition zone, the resistance of the cell changes depending on the intensity of the infrared radiation source. In conjunction with a constant current, this variable resistor generates a variable voltage that is amplified. The amplified variable voltage is in turn converted into a variable current which is fed to the main amplifier via the shielded cable. In the main amplifier, the variable current flows through a resistor, at which a variable voltage is then dropped, which is fed to a first integrated amplifier stage via a capacitor. After this amplification, the alternating signal representing the flame fluctuations is sent to an integrated filter circuit. The filtered signal is fed to a half-wave rectifier and an integrator. The resulting DC signal \ fird is compared with a manually set integrator gl @ ± ch @ ignal of the background and then processed with the aid of time delay and digital circuits in a way that is necessary to control the burner.

The connection unit receives the pre-amplified signals coming from the detector head and transmitted via the long shielded cable, which correspond to the infrared fluctuations in the combustion zone of the combustion system scanned by the photosensitive cell ) a rectifier part, 3) a signal level detector part, and 4) a delay part. The first part contains circuit means for the further

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Amplification and for filtering that part of the signal that lies between 45 and 60 Hz. All other frequencies are rejected to a certain extent. The second part contains circuit means for reshaping the Output alternating signal of the first part in a proportional direct signal level. The third part has a Circuitry that compares the output signal of the second part with a preset limit value to determine whether there is a flame or not. The fourth part has an adjustable time delay circuit in the event of a flame failure, before an output signal F (flame) and an output signal P (no flame) on the flame failure speak to. There is no delay in the initial detection of the flame.

The invention provides a frequency characteristic curve in the light source frequency range from 45 to 60 Hz, with a minimum of unwanted noise signals, i.e. between -1 and +1 dB (50 Hz corresponds to 0 dB) the amplified signal fluctuations. Since the signal transmitter unit or the detector head is located in a small opening in the Wall of. Firing system is attached, problems arise here avoided, as they occur with conventional sensors, in which an elongated sight tube with an ultraviolet-sensitive Cell protrudes into the furnace to monitor the flame. As a result of the intense heat there is often a destruction of these pipes, and the occurring large thermal stresses reduce the accuracy of the sensor. The subject matter of the invention therefore indicates when using special advantages in coal-fired plants.

In gas-fired systems with oil-fired ignition devices, the infrared detector designed according to the invention can between the gas flame and the oil flame differentiate and therefore indicate whether the ignition device is in operation. Conventional ultraviolet detectors can

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do not assume such a function. Furthermore, the subject matter of the invention is designed in such a way that it also has
can be serviced or repaired quickly and easily at its place of use and that the individual units are easily detachably connected to each other for quick replacement.

A preferred embodiment of the invention is described with reference to drawings. Show it:

Fig. 1 is a schematic view of a dynamic Infrared flame detector arrangement according to the invention,

Figure 2 is a side view of a coal-fired one
Boiler with a flame end tektorkopf designed according to the invention, which is housed in an opening in the boiler wall,

3 is a block diagram of the flame detector arrangement;

4 is a circuit diagram of the entire arrangement,

Fig. 5 is a frequency characteristic curve of the main amplifier with the output signal is a function of
the light source frequency and

6 shows a partial section through a gas-fired burner with an oil-fired ignition device and a Flame detector head according to the invention

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1 shows a dynamic flame detector arrangement which is responsive to infrared radiation, a detector head 10 designed as a compact unit, an elongated, shielded cable 12 and includes a remote connector unit 14 which may be a considerable distance from the detector head 10 The detector head 10 has a short tubular extension piece on, which forms an optical nipple 16, which in a small, its dimensions corresponding opening in a wall 18 of a furnace of for example a boiler 20 is fitted. The combustion chamber also contains a burner 22 which can generate a flame 24. The detector head 10 supplies pre-amplified, the flame fluctuations corresponding signals which are transmitted via the cable 12 to the connection unit 14, where the preamplified Signals are amplified again and used to control and / or display the on / off state of the flame 24 digitally are processed.

As can be seen from Fig. 2, the line of sight 26 of the optical system is in the short tubular shape Nipple 16 parallel to burner 22, but within the iAiftregisters 28, and through the neck 30 of the kettle 20 · The Flame 24 is in the viewing direction of line of sight 26 Combustion zone 34 is surrounded by a conical bell 32 of smoke and coal dust when the burner 22 is operating.

As can be seen from FIG. 3, the detector head 10 shows a box containing an infrared sensitive cell 36 and a small solid body preamplifier circuit 38 contains. The cell 36 is arranged together with the optical system in such a way that it is exposed to the radiation which emits the flame to be observed. The cell 36 and the preamplifier circuit 38 form the flame fluctuations, that occur in the burn zone into a corresponding electrical signal that is transmitted through

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the cable 12 to the connection unit 14 is preamplified. That Cable 12 is shielded and contains two insulated conductors As can also be seen from FIG. 3, the connection unit which is a distance from the detector head 10 contains 14, a main amplifier circuit 40.

The terminal unit 14 makes use of integrated circuits and comprises the following four main parts: (1) a main amplifier and filter part 40, (2) a rectifier part 42, (3) a signal level detector part 44 and (4) a time delay part 46 with output signal circuits, their Output signals F, F and F ₁ mean flame "no flame" or "momentary flame". The circuit of part 40 amplifies that portion of the signal which lies between 45 and 60 Hz and rejects all others to a certain extent The circuit of section 42 converts the AC output signal of the amplifier and filter section 40 to a proportional DC level. The circuit of section 44 compares the output signal of the rectifying section 42 with a preset limit value to determine whether a flame is present or not The output of the level detector section 44 is fed to the time delay section 46, the circuit of which is a one-time delays the flame output signals F (flame) and F (no flame). The flame output signal Fj is not subject to any delay.

The frequency characteristic 50 of the main amplifier and filter part 40 shown in FIG. 5 increases a light source frequency of about 75 Hz to a maximum output signal of +2 dB and then gradually decreases, as shown. The output signal is shown in dB, with 50 Hz assigned to a standard of 0 dB are. The main burn zone is very rich in such frequencies. The tail or background flame frequencies are on the other hand outside the curve 50. The optimal fre-

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frequency range is selected between 45 and 60 HzFrequencies, that are considerably above or below this range are cut away. This makes the usable one Area placed in the front part of the curve 50, whereby unwanted noise is effectively avoided.

From Fig. 4 it can be seen that the photosensitive Cell 36 has pin-like terminals A, B and C that allow a quick plug connection with corresponding sockets. The jacks are on the preamp circuit connected. The preamplifier circuit 38 has a positive supply voltage line 52, a negative line 54 and a ground line 56. These lines are connected to corresponding lines of the cable 12 via plug-in pin socket connections E, J or H are connected, so that the connection can also be made quickly and easily at this point or can be interrupted. As a result, it is possible to replace the entire detector head 10 and or or for repairs on site quickly and easily to remove. The cell 36 converts variable radiation into variable resistance.

A resistor R5 »a capacitor C2 and a diode D2 are connected to one another in such a way that they act for two Constant current sources form a constant voltage source. The capacitor C2 serves as a filter for the constant voltage source. A resistor R6 and a transistor Q4 together with the constant voltage source constitute a constant current source for cell 36. Resistor R4, transistor Q5, and resistor R2 form one to the Lines 52 and 54 connected in series to for biasing a Darlington pair of transistors Q1 and Q2 also connected between lines 52 and 54 lie to form a constant current source «, a transistor Q3 and a resistor R3 are used to match the resistance between the cell circuit (high resistance) and

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the output transistors a. (low resistance). A capacitor C1 only couples the AC component of the flame signal to the output transistors Q1, Q2

In operation, variable infrared radiation strikes cell 36. The resistance of cell 36 changes depending on the intensity of the infrared source. The variable cell resistance generates in connection with the constant current at the terminal A of the cell 36 a voltage · This variable voltage is generated via the circuit comprising the transistor Q3, the resistor R3 and the Capacitor C1 fed to output transistors Q1, Q2 The transistors Q1 and Q2 convert the variable voltage into a variable current signal, which is transmitted via the shielded Cable 12 is fed to a main amplifier resistor R27.

The connection unit 14 receives the output signal of the cable 12 via quickly disconnectable pin socket connections or connections G and I ₉ which allow easy replacement of the unit 14 at the point of use.The main amplifier circuit has a positive voltage line 58 which is connected to the positive terminal 60 of a unilateral DC power source of 12 ¥ is connected · A resistor RI5 and a diode D22 are in series between the positive ones. Voltage line 58 and a ground line 62 are connected. Resistor R27 is connected to ground line 62 in order to provide a reference voltage for the operational amplifier, since the amplifier operates on the one-sided supply voltage (+12 V).

A capacitor C10 forms for a first amplifier stage 64 of the received signal © AC coupling. Unwanted high frequencies are generated through a ■ capacitor C9, the resistor R27 clialtet in parallel The first stage 64 of the signal amplifier circuit is derived to ground contains a resistor. R19, an in-

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> ■■ 245H49

integrated circuit IC2, a resistor R28, a capacitor C13, a resistor R22, an adjustable resistor R11 and a capacitor C12. The voltage gain of the first gain stage 64 can be adjusted by adjusting of resistor R11 can be changed. A main frequency filter circuit 66 includes a capacitor C5, a resistor R17, a resistor R16, a resistor R14, a capacitor C3, a capacitor C6, an integrated circuit IC3 »a capacitor C7, a resistor R18, a resistor R33 and a capacitor C44. The frequency filter circuit 66 attenuates the high and low frequencies of the flame signal, preferably above and below a selected range of 45 to 60 Hz.

It is further provided in the unit 14 a Halbweggleichrichter-integrator and filter circuit 68, an integrated circuit IC4, a diode D33 ", a diode D4, a resistor R21 _for a capacitor C8, a diode D5, a resistor R222, a capacitor C111 and includes a resistor R13. The circuit 68 serves to rectify the filtered flame signal and provides a DC voltage to the base of a transistor Q22.

The transistor 022 and a resistor R22 are connected as an emitter follower circuit 70 which is connected between the Rectifier integrator circuit 68 and an integrated comparator circuit 71 as well as connections to a measuring device M decoupling.

A voltage divider circuit is used to generate the background voltage 72 with a resistor R8, an adjustable resistor R10 and a resistor R9 are provided. The desired background setting is achieved by adjusting resistor R10.

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The comparator circuit 71 includes an integrated circuit IC5, a resistor R25 and a resistor R12. The comparator circuit 71 is used for comparison of the direct current flame signal with the background signal and generates a suitable output signal for a circuit 79. Plug pins 76 and 78 are used to quickly disconnect the measuring device M from the unit 14 for quick replacement for calibration and / or repair

The circuit 79 is an integrated circuit IC1 which serves as a driver stage for the following circuits including a time delay circuit 80. The circuit 80 comprises, in addition to the integrated circuit 79, a diode D11, a resistor R7, an adjustable resistor R66, a resistor R55, a capacitor C11, a transistor Q11 and a resistor R44. Circuits 82, 84 and 86 are designed as integrated circuits IC1 and have three flame signal compensation circuits 88, 90 and 92 for the signal F and the signal f with delay and for the signal Fj. without delay on

The variable current driven through the resistor R27 v @ a of the preamplifier circuit 38 generates a corresponding variable voltage at the resistor R27, which voltage is fed to the first amplification stage 64 via the capacitor C10. The amplified AC signal then goes to the filter section 66, the filtered signal is fed to the half-wave rectifier and integrator section 68. The resulting AC signal is compared in the comparator stage with the background signal and then from the digital circuit 79 »the time delay circuit 80 and the digital circuits 82 _g 84 and 86 processed automatically

As seen from Figure 5 seen _s ^ the main filter part 66 is as shown in FIG. 4, the high buffering and

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low frequencies above 60 Hz and below 45 Hz of the frequency characteristic 50 of the infrared cell 36, and the preamplifier 38 and the main amplifier 64 are used to achieve optimal results. Since the best frequency range is between 45 and 60 Hz, the front section will be the frequency characteristic 50 is used. The frequencies well above 60 Hz are cut away, to avoid noise interference.

According to FIG. 6, the detector head 10 designed according to the invention is used in a gas-fired furnace 21, which has a main burner 23 charged with gas and a flame ignition device 25 fed with oil. The burner 23 and the ignition device 25 extend through openings in a furnace wall 19. The optical nipple 16 of the detector head 10 is also inserted in an opening in the furnace wall. The line of sight 17 of the probe in this case looks both at the zone of a gas flame 29 as well as the zone of an oil flame 27 of the ignition device. The infrared detector is capable of detecting the oil fired To distinguish pilot flame from gas-fired flame. One can therefore determine whether the oil-fired Ignition device is in operation. This is not possible with conventional ultraviolet flame detectors.

The invention is also applicable to coal and oil fired boilers. In particular, it will be of great benefit used in coal-fired boilers as the use of infrared radiation is one of the only successful ones One possibility is to carry out flame detection in a coal-fired boiler. In a coal-fired In fact, smoke and dust occur in ovens, so that it is very difficult, if not impossible, to find them or the absence of the flame to be determined using other detection methods. So far it was for flame detection It was common to use an ultraviolet probe, which required a relatively long pipe that was

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extended into the furnace.This pipe led right up to the flame and was therefore exposed to thermal influences, which very quickly leads to an inaccuracy of the optical In addition, the ultraviolet light necessary for the proper operation of an ultraviolet detector was caused by the smoke present in the furnace and Coal dust covered. These problems do not arise with the subject matter of the invention, since, on the one hand, infrared radiation and on the other hand the detector head is flush with the furnace wall.

The invention is thus to be seen in a dynamic infrared flame detector arrangement with a compact signal transmitter head which is arranged in a small opening in the wall of a furnace that is fired with fossil fuel. The signal transmitter head contains a solid-state preamplifier circuit and an infrared sensor which is focused on the burning zone in order to scan flame fluctuations and convert them into correspondingly preamplified signal current fluctuations, which are then transmitted via a shielded cable to a remote signal receiver connection unit with a transistorized main amplifier filter and rectifier circuit. The signal receiver connection unit is able to distinguish the flame fluctuations from the background radiation. The main amplifier filter and rectifier circuit are assigned an integrated control circuit which digitally processes the signal fluctuations and automatically controls flame indicators and / or alarm devices, depending on the state in the flame combustion zone.

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Claims (1)

Claims ~ · - ^ ■ * M. ' Dynamic infrared flame detector for use with fossil fuel burners. In one Firing system with through openings in the wall to accommodate the burners, characterized by one in a passage opening in the wall of the furnace attached signal transmitter unit (10) for converting flame fluctuations into corresponding pre-amplified signal fluctuations with a preamplifier circuit (38) and with an infrared sensor which has an optical nipple (16) directed towards the flame burning zone, and through a remote signal receiver unit (14) connected to the signal transmitter unit via a shielded cable (12) a main signal amplifier circuit (40), which via the cable from the preamplifier circuit the signal fluctuations receives, and with one of the main amplifier circuit associated integrated control circuit (42, 44, 46) which digitally processes the amplified signal fluctuations, 2 · Flame detector according to claim 1, for use in a coal-fired plant in which smoke and coal dust occur in the combustion zone,
characterized in that the optical nipple (16) of the infrared sensor is arranged outside the combustion zone in order to effectively protect the signal transmitter unit from damage by the intensity of the flame of the burner, and in that the small preamplifier circuit (38) is transistorized and for converting the from the infrared radiation emanating from the combustion zone, a photosensitive cell (36) which has a variable resistance corresponding to the infrared fluctuations, a constant voltage source (R5, C2, D2) and a constant current source (R6, Q4) connected to the cell (36), the resistance being of the cell when the va- 509825/0666 Riable infrared radiation as a function of the infrared radiation intensity changes and the cell emits a corresponding variable voltage, which is converted into a variable signal current is converted, which represents the pre-amplified signal fluctuations and via the shielded cable (12) is supplied to the main signal amplifier circuit (40). 3. Flame detector according to claim 1 for a gas-fired system, the gas burner of which has an oil-fired ignition device assigned, characterized in that the preamplifier circuit (38) for converting the infrared radiation the oil-fired ignition device in the signal fluctuations contains a photosensitive cell (36) and that the control circuit is able to distinguish between the oil-fed pilot flame and the gas-fed combustion flame to indicate whether the oil-fired one Ignition device is actually in operation. 4. Flame detector naeh © inern of the preceding claims, characterized g @ k @ aas © I © hnet ₉ that the frequency range, the iron over the infrared sensor. wachten Lichtschtmnkimgsn ά <§τ · Flaaaenvarbreiiaungszone a range from 45 to 60 Hz and that switching means are provided that cut away the light fluctuations occurring above and below this range in order to keep infrared background fluctuations and noise phenomena as low as possible. 5. Flame detector according to one of the preceding claims, characterized in that the Hauptsignalve ^ stärkersehaltung characterized by a resistance circuit (R27) for generating a variable voltage corresponding to a current supplied by the pre-amplifier circuit (38) of the switch unit (10), _f by a capacitor circuit (C10) by 509825/0666 an integrated first amplifier circuit (64), the input of which for supplying the variable voltage across the capacitor circuit to the output of the resistor circuit is coupled and at the output of an amplified alternating current signal occurs, the frequency of the flame fluctuations and by an integrated connected to the AC signal output of the first amplifier circuit Filter circuit (66) whose frequency transfer characteristic is rich in primary combustion zone frequencies, while the background frequencies fall outside this transfer curve and are attenuated by the filter circuit will. 6, Dynamic infrared flame detector head, characterized by a signal transmitter unit (10) with an infrared sensor, a optical nipple (16) and one responsive to infrared radiation Cell (36) and by a small solid-state circuit (38) for pre-amplifying infrared signals that the Cell (36) receives via the nipple (16), and for driving of the pre-amplified signals through a conductor cable (12) a remote receiver connection unit (14). 7. Flame detector head according to claim 6, characterized in that the solid-state circuit (38) is characterized by a positive and a negative DC voltage supply line (52 and 54) for generating a constant voltage a resistor (R5) and a diode (D2) connected in series to the lines through one of the resistor (& 5) capacitor (C2) connected in parallel for filtering the constant voltage, through a resistor (R6) and a Transistor (Q4) connected in series between the positive and the negative line lie, by means of connecting the base of the transistor (04) to the negative side of the capacitor (C2) connect so that for the cell (36) for reshaping 509825/0666 variable infrared radiation is provided in a variable resistor a constant current source, are through a resistor (R2) and _g a transistor (Q5), the current source for generating a constant in series between the lines, by two connected in Darlington output transistors (Q1, Q2), which are connected to the two lines and for biasing with a constant current to the latter transistor (Q5) through a transistor (Q3) and a resistor (R3) connected in series with each other and for resistance matching between the cell circuit (36) and the output transistors (Q1, Ö2), and by a capacitor (Cl), which only supplies the alternating current component of the flame signal to the output transistors (Q1, 02). 8. Flame detector head according to claim 7, characterized in that the cell (36) is connected to a ground line (56) is that the positive, negative and ground lines (52, 54 and 56) with quick-release connector pins (E, J and H) are provided that fit into associated outer sockets, and that the cell (36) is also provided with fast separable pins (A, B, C) which fit into associated circuit sockets ^ so that the cell quickly and is easily removable or replaceable. 9. Flame detector head according to claim 7 or 8, since you are marked raw, that when the lines are connected to a constant voltage source and when the cell is irradiated with infrared radiation of variable intensity, the cell resistance of the radiation intensity dependent changes that the variable cell resistance carries out together with the constant current. at the positive movement of the line © (36) there is an amiable voltage generated and that this variable Spamumg to the output transistors (Q1, 02) is coupled to this voltage in convert a correspondingly irariafelen current «which preconverts 509825/06 "^ represents the strongest output signal that is then transmitted, 10. Flame detector head according to one of claims 6 to 9, characterized in that that the solid-state circuit (38) and the infrared sensor cell (36) are housed in a compact housing, portable and with the optical nipple (16) in a small through opening in the wall of a furnace can be fitted to observe the combustion zone, 11. Dynamic infrared flame detector, characterized by an infrared burn detector head (10) having an infrared sensitive Cell (36) and a solid state preamplifier circuit (38) for amplifying a signal generated by the cell with a low level for the purpose of transmission of the signal to a remote receiver (14) through a shielded signal conductor cable (12) connected to the Preamplifier circuitry in the detector head is connected to the preamplified signal to the remote Receiver, and through a main amplifier control circuit connector unit with small integrated solid-state circuits (40, 42, 44, 46) for further amplification, Process and display the infrared radiation detected by the cell. 12. Flame detector according to claim 11, characterized in that the detector head circuits and the associated circuits of the shielded cable via quick-disconnect pin-socket connections are interconnected so that the head is easily separated from the cable and easily interchangeable is. 509825/0666 245 UA9 13. Flame detector according to claim 11 or 12, characterized in that the cable circuits and associated circuits of the Main amplifier control circuit connection unit connected to one another via quick-release pin and socket plugs so that the connection unit can be separated from the cable easily and without further ado 14. Flame detector according to claim 11, characterized in that that the cable is connected to both the detector head and the connection unit via quick-release plugs Flame detector according to one of Claims 11 to 14, characterized in that the detector head (10) is equipped with an optical nipple (16) which, aligned with the flame of a combustion zone to be monitored, can be fitted into a small opening in the wall of a furnace is that the cell can see the combustion zone through both the air throat (30) and the mist surrounding the combustion zone (32) ", 16. Dynamic infrared flame detector for receiving pre-amplified signals generated by infrared radiation via a shielded cable from a remote infrared detector head with an optical nipple, which is fastened in a small opening in the wall of the furnace chamber of a boiler,
characterized in that four main parts are provided from an amplifier and filter (40), from a rectifier (42), from a signal level detector (44) and from a time delay (46) that the first part contains circuit means which only contain that frequency component of the amplify preamplified signal that falls between 45 and 60 Hz, and the 509825/0666 the remaining frequency components substantially reject that the second part contains circuit means that the Convert the AC output signal of the first part into a proportional DC level that the third Part contains circuit means which the direct current output signal of the second part with a preset limit value compare to determine whether or not there is a flame and that the fourth part is circuit means which provide an adjustable delay time when the flame is extinguished before the signal F (flame) and the signal F "(no flame) from the third part to one respond to delayed flame fault, and the no delay time to be provided when the flame is detected first. 509825/0666 Empty soap