CN1009575B - Photoelectric smoke detector - Google Patents

Abstract

The light emitting element generates light pulses at a fixed period, and the photosensitive detection element installed opposite to it receives the light pulses attenuated by smoke and detects the fire from them. When the power is turned on, the microcomputer in the photosensitive detection element stores and retains the first photosensitive detection data as initial data in the memory and it is not erased by temporary power failure. The photosensitive detection data is converted into correction data using the correction ratio to perform contamination correction and identify the fire accordingly. The correction ratio is corrected when the correction period reaches 50 minutes, wherein the correction ratio is increased or decreased by a small value only in each correction period until the photosensitive detection data coincides with the initial photosensitive detection data.

Description

The present invention relates to a photoelectric smoke detector, wherein the light-emitting element and the photosensitive detection element are arranged oppositely and keep a fixed distance from each other, and the light is weakened due to the smoke entering the area between the arranged light-emitting element and the photosensitive detection element, according to This diminution of light detects the occurrence of a fire; more particularly, the present invention relates to a photoelectric smoke detector in which changes in the photosensitive detection signal due to contamination of the optical system are corrected.

Heretofore, in photoelectric smoke detectors in which the light-emitting element and the photosensitive detection element are arranged opposite to each other, after a long period of use, dust is deposited on the windows of the light-emitting element and the photosensitive detection element, which reduces the signal level of the photosensitive detection, if When the photosensitive detection signal level drops below a threshold value for judging the occurrence of a fire due to dust, an erroneous fire signal will be output. Therefore, cleaning work must be carried out regularly to remove dust.

However, since the cleaning work to remove the dust is troublesome, a device in which the photosensitive detection signal is automatically corrected according to the amount of deposited dust has been considered. For example, a photoelectric smoke detector is known from U.S. Patent No. 4,317,113.

In this photoelectric smoke detector, the gain of the operational amplifier used to amplify the photosensitive detection signal is gradually changed according to the degree of signal attenuation due to the deposition of dust. When the photosensitive detection is weakened due to dust deposition, the amplification The gain will be increased by an amount equal to the attenuation, so it is possible to obtain a photosensitive detection signal in the same state as without dust deposition.

However, the smear correction using the gain control of the operational amplifier has the following problems.

The first question is:

As a method of changing the amplification gain, the resistance network provided in the operational amplifier feedback circuit changes its impedance due to on/off control of multiple analog switches. However, analog switches generally have an on-state resistance of about 100 to 300 ohms, and due to this on-state resistance, the feedback impedance cannot be accurately determined. Therefore, it is difficult to perform linear gain control by means of switching.

The second question is:

In order to realize the linear gain control by switching the switch, the impedance must be controlled by setting a plurality of variable resistors, which makes the circuit complicated and the control operation also becomes cumbersome.

The third question is:

On/off control of a plurality of analog switches requires a bidirectional counter, so there is a problem of complicating the gain control circuit.

On the other hand, in the method of correcting contamination by means of gain control, the initial photosensitive detection data and the current photosensitive detection data are regularly compared, and the gain of the operational amplifier is changed according to the difference between the two data, thereby Eliminate the difference. However, in the case of progressively increasing smoke concentrations, such as in a smoky fire, such signal attenuation is also corrected by the amplification gain control, so that there is a risk that the fire will not be detected.

In addition, since the initial photosensitive detection data for contamination correction is stored when the power is turned on, for example, after a fire signal is output to the receiver due to smoke detection, even after the power is turned off once for recovery When it is turned on and then turned on again, the photosensitive detection data dropped due to smoke at this moment is re-stored as the initial photosensitive detection data, so there is a risk that the recovered fire situation cannot be detected.

Furthermore, the threshold value for judging the fire determined by the initial photosensitive detection data stored due to power-on also becomes abnormal, and as a result, there is a risk of generating an error alarm or a false alarm.

The object of the present invention is to provide a photoelectric smoke detector in which the photosensitive detection data is input as uncorrected, and the corrected photosensitive detection data is obtained from the calculation process based on the correction coefficient of the time.

Another object of the present invention is to provide a photoelectric smoke detector in which the initial photosensitive detection data obtained when the power is first turned on is stored, and the pollution correction is performed according to the initial photosensitive The difference between the detection data and the current photosensitive detection data is corrected for a correction ratio, and the current photosensitive detection data is multiplied by the correction ratio to obtain corrected photosensitive detection data.

Another object of the present invention is to provide a photoelectric smoke detector, wherein when a difference occurs between the initial photosensitive detection data and the current photosensitive detection data, the correction ratio is only corrected by an amount equal to a predetermined small value.

Still another object of the present invention is to provide a photoelectric smoke detector in which the storage of initial photosensitive detection data can be maintained for a fixed period even after the power supply is turned off.

Still another object of the present invention is to provide a photoelectric smoke detector in which an abnormal data is prevented from being stored by checking the stored initial photosensitive detection data to determine whether an abnormal data is within a predetermined range.

These and other objects, features and advantages of the present invention will appear from the following description taken in conjunction with the accompanying drawings.

Figure 1 is an explanatory diagram showing the system arrangement of an embodiment of the present invention;

Fig. 2 is a block diagram showing the system arrangement of the present invention;

Figure 3 is a block diagram showing one embodiment of the receiving unit of the present invention;

Fig. 4 is a general flowchart showing the program control process of the receiving unit;

Figure 5 is a functional block diagram showing processing circuitry for smear correction in accordance with the present invention; and

Fig. 6 is a flow chart showing the smear correction process of the receiving unit due to program control.

Fig. 1 is an explanatory diagram showing the overall arrangement of an embodiment of the present invention as an extinction type separation type photoelectric smoke detector.

In FIG. 1, reference numeral 10 denotes a receiver, which is installed in a central monitoring room or the like. The receiver 10 receives a fire detection signal from a photoelectric smoke detector and generates a fire alarm while displaying a fire area. Receiver 10 also receives inspection alarm signal and carries out alarm indication when breaking down in a photoelectric smoke detector so that this photoelectric smoke detector receives inspection, draws a signal line 16 from receiver 10, and it also serves as power supply line; Check the signal line 18 and a common line 20. The photosensitive detection elements 12a, . . . 12n in a plurality of photoelectric smoke detectors are connected to these signal lines 16, 18 and 20.

In the photoelectric smoke detector of the present invention, a single photoelectric smoke detector is composed of a combination of a photosensitive detection element 12a and a light emitting element 14a, or a combination of a corresponding photosensitive detection element 12n and a light emitting element 14n.

For example, reference will be made to a single photoelectric smoke detector consisting of a photosensitive detection element 12a and a light emitting element 14a. In this example, the light emitting element 14a is arranged opposite to the photosensitive detecting element 12a and maintains a predetermined distance in the range of 5-100 meters, for example, 15 meters. A pair of signal lines 22 and 24 drawn from the photosensitive detection element 12a are connected to the light generating element 14a. This connection of signal lines 22 and 24 is the same as the connection of photosensitive detection element 12n and light emitting element 14n. In addition, the corresponding photosensitive detection elements 12a, . . . 12n and light emitting elements 14a .

Fig. 2 is a block diagram showing the arrangement of the system in Fig. 1, wherein photosensitive detection element 12a and light emitting element 14a, and Both the photosensitive detection element 12n and the light emitting element 14n are arranged opposite to each other and keep a predetermined distance respectively. The light emitting elements 14a and 14n are provided with a light emitting device 26 . The light-emitting control signal is transmitted from the photosensitive detection elements 12a and 12n to the light-emitting device 26 through the signal lines 22 and 24, thereby stimulating the light-emitting device 26 to emit light. The signal lines 22 and 24 are also used as power lines. The light emitted from the light emitting device 26 enters the photosensitive detection device 28 equipped with the photosensitive detection elements 12 a and 12 n through the smoke detection area 30 . Therefore, when the photosensitive detection element 12a and the light emitting element 14a, or the photosensitive detection element 12n and the light emitting element 14n are coupled to the surface of the ceiling or similar structures, the optical axis should be adjusted so that the light from the light emitting device 26 enters the photosensitive detection element accurately. Device 28. On the one hand, the light emitted from the generating device 26 passes through the smoke detection area 30 and enters the photosensitive detection device 28 , where the light is attenuated due to the presence of smoke in the smoke detection area 30 . In this way, light with an intensity attenuation dependent on the smoke concentration is input to the photosensitive detection device 28 .

Each of the photosensitive detection elements 12a and 12n is provided with a control section using a microcomputer, respectively. After adjusting the optical axis during installation or similar adjustments, the initial power supply and the photosensitive detection data excited when the power is turned on are stored in the memory of the microcomputer as the initial photosensitive detection data. The threshold value for determining the occurrence of fire is calculated on the basis of the initial photosensitive detection data stored in the memory, and whenever the photosensitive detection data is obtained, it is compared with the threshold level to identify the occurrence of fire. Once it is determined that a fire has occurred, a fire signal is transmitted to the receiver 10 via the signal line 16, which also serves as a power supply line. In addition, as will be explicitly described hereinafter, the initial photosensitive detection data stored in the memory of the microcomputer is used in the control process of smear correction. When the initial photosensitive detection data exceeds the correction limit during the control process of contamination correction, a check alarm signal indicating that the contamination correction has reached the limit is output to the receiver 10 through the check signal line 18 . Furthermore, when the initial photosensitive detection data stored in the memory when the power is turned on for the first time is abnormal, the inspection signal line 18 also transmits an alarm signal for inspection to the receiver 10 .

Fig. 3 is a block diagram showing the circuit arrangement of a photosensitive detecting element used in the photoelectric smoke detector using a microcomputer as a control portion of the present invention.

In FIG. 3, the constant voltage circuit 32 receives power from the receiver and outputs a power supply voltage of 16 volts. A capacitor 34 having a large capacitance value is connected to an output terminal of the constant voltage circuit 32 . Even if the power supply from the receiver is temporarily interrupted due to a power failure or the like, since the voltage charged in the capacitor 34 is still supplied to the microcomputer as the control section for a fixed period of time, it is possible to store The initial photosensitive detection data Di in the memory of the microcomputer keeps its storage. As a result, even if the power supply from the receiver is temporarily interrupted, the initial photosensitive detection data Di will not be erased.

Another function of the capacitor 34 is to stabilize the output voltage of the constant voltage circuit 32 .

Reference numeral 36 denotes a control unit employing a microcomputer. For example, an 8-bit microcomputer, specifically, µPD80C48C manufactured by NEC Corporation, was used. Power supply to the control unit 36 employing a microcomputer is performed by a constant voltage circuit 38 . The constant voltage circuit 38 converts the output voltage of 16 volts from the constant voltage circuit 32 into a constant voltage of 5 volts and supplies it to the control unit 36 .

When the power is turned on, the power reset circuit 40 operates and outputs an initial reset signal to activate the microcomputer within the control unit 36 . In response to this initial reset signal, the control unit 36 performs light emission control and light reception control, and stores initial photosensitive detection data obtained due to the light emission and light reception control immediately after the power is turned on, into the memory 42 . When the initial photosensitive detection data is stored in the memory 42, a data check is performed to determine whether the initial photosensitive detection data is within a predetermined range. When it is within this range, initial photosensitive detection data is stored in memory 42 . Conversely, when it is outside this range, an alarm signal for checking is output to the receiver.

After turning on the power and completing the storage process of the initial photosensitive detection data according to the output of the power reset circuit 40, the microcomputer in the control unit 36 will stop the program control and return to the standby state. Subsequent operations of the control unit 36 are performed according to pulses from the master clock. The master clock circuit 44 outputs a clock pulse to the control unit 36 every fixed period ranging from 2 to 4 seconds. According to this clock pulse, the control unit 36 executes light emission and light reception control, inputs the photosensitive detection data actually obtained at this time, and obtains the corrected photosensitive detection data obtained due to the operation process of smear correction, thereby according to the corrected photosensitive detection data. The comparison between the detection data and the threshold value identifies the fire.

The light emission control unit 46 receives the light emission control signal outputted according to the master clock due to the operation of the control unit 36 immediately after the power is turned on, and outputs a control signal to the light emitting element, thereby energizing the light emitting element by using a capacitor discharge pulse. of light emitting devices. Because of this, the light for detecting smoke is emitted to the photosensitive detection element. Similar to the lighting control unit 46, the light The reception control unit 48 operates according to the light reception control signal from the control unit 36, which operates according to the output of the power reset circuit 40 immediately after the power is turned on or according to the clock pulse of the main clock circuit 40. That is, the light reception control unit 48 operates a constant voltage circuit 50 , thereby supplying a power source with a voltage of 10 volts to the photosensitive detection circuit 52 . The light reception control unit 48 also operates the reference voltage generator 54 to generate a reference voltage of 2.5 volts for A/D conversion, and also operates the power supply voltage monitoring circuit 56 for monitoring the output voltage of the constant voltage circuit 32 .

The photosensitive detection circuit 52 includes a photosensitive detection device 28, an amplification circuit and a peak hold circuit therein. The photosensitive detection circuit 52 receives the emitted light from the light emitting device by the photosensitive detection device 28, converts it into an electrical signal, and amplifies the photosensitive detection signal to a specific level by the amplifying circuit. At the same time, the photosensitive detection circuit 52 holds the peak level of the photosensitive detection signal through the peak hold circuit and outputs this signal. The photosensitive detection signal output from the photosensitive detection circuit 52 is supplied to an analog/digital converter 58 and converted into a four-bit digital signal, and is input to the control unit 36 as photosensitive detection data. The analog-to-digital converter 58 converts the photosensitive detection signal from the photosensitive detection circuit 52 into a digital signal based on the 2.5 volt reference voltage from the reference voltage generator 54 . In addition, a sensitivity determination signal from the sensitivity determination circuit 60 is also input to the A/D converter 58 . The sensitivity determination circuit 60 takes out the output voltage of the reference voltage generator 54 as different divided voltages through the conversion of a rotary switch or similar structure, thereby determining different threshold values for judging fire conditions in the control unit 36 . The sensitivity determination signal from the sensitivity determination circuit 60 is also converted into a digital signal by the A/D converter 58 and supplied to the control unit 36 , and in turn, the power supply voltage monitoring circuit 56 monitors the 16 volt output voltage of the constant voltage circuit 32 . When the power supply voltage drops to a level, such as lower than 12 volts, the monitoring circuit 56 notifies the control unit 36 of the abnormality of the power supply through the analog-to-digital converter 58 .

The fire signal output circuit 62 receives an output generated when the control unit 36 judges the occurrence of a fire and performs switching operation and makes the fire signal current flow between the signal line 16 that is also used as a power line and the common circuit drawn from the receiver 10. The wires 20 flow between them, thereby transmitting the fire signal. When the photosensitive detection element is determined to be abnormal by the control unit 36 , the inspection signal output circuit 64 makes an inspection current flow between the inspection signal line 18 and the common line 20 drawn from the receiver 10 , thereby transmitting an inspection signal. The fire signal current of the fire signal output circuit 62 and the check signal current of the check signal output circuit 64 can be, for example, up to 30 mA, respectively. On the other hand, in the case where a fire signal or a check signal is not output, these currents are compressed to an average monitor current of about 250 microamperes.

FIG. 4 is a flow chart showing the control process of the photosensitive detection element by the microcomputer in the control unit 36 in FIG. 3. Referring to FIG.

When the power is turned on for the first time, the power reset circuit 40 outputs a power reset signal and the microcomputer in the control unit 36 starts operation. Then in the program block 66, the microcomputer completes the light-emitting and light-receiving control. Due to the control of light emission and light reception, the photosensitive detection signal is activated by the photosensitive detection circuit 52 of the photosensitive detection element, so that the photosensitive detection signal Dn after analog/digital conversion is input into the box 68 . In the next identification block 70, a check is made to determine if the system is in the initial state. When it is determined in block 70 that the system is in the initial state because the power on has completed the power reset, an identification block 72 follows. In block 72, a check is made to determine whether the photosensitive detection data Dn obtained for the first time is within a predetermined range. When the first photosensitive detection data Dn is determined to be outside this range, block 74 follows and a check alarm signal is output to the receiver. That is, when the photosensitive detection data Dn excited immediately after the power supply is turned on is outside the predetermined range, this means a case, for example, that the photosensitive detection is caused by the skew of the optical axis between the photosensitive detection element and the light emitting element. The signal level is very low. Therefore a detection alarm occurs to readjust the optical axis. On the other hand, when the photosensitive detection signal Dn exceeds the predetermined range, it can be considered that the gain control of the amplifier or the like provided in the photosensitive detection circuit 52 is not appropriate. Also in this case, check alerts for recalibration occur in a similar manner.

On the other hand, when the photosensitive detection data Dn is within the predetermined range, then enter the subsequent block 76 and the photosensitive detection data Dn will be stored in the memory 42 of the microcomputer as initial photosensitive detection data Di. As described above, the power supply from the receiver is completely cut off, due to the charge in the capacitor 34 equipped with the constant voltage circuit 32, the initial photosensitive detection data Di stored in the memory 42 will keep its storage for a predetermined time, so that it Will not be erased due to temporary power outages or the like.

After the storage of the initial photosensitive detection data Di is completed, the processing program enters the contamination correction process in block 78 . This smear correction process will be described in further detail with reference to the block diagram in FIG. 5 and the flowchart in FIG. 6 .

In the stain correction process of block 78, the photosensitive detection data Dn is multiplied by a correction ratio to correct the light attenuation caused by the stain on the photosensitive detection element and the light-emitting element window, thus obtaining A corrected photosensitive detection data Dn in the same situation as when the window is not stained.

In block 80, a fire is identified by comparing the corrected photodetection data Da obtained from the stain correction process performed in box 78 with a threshold value calculated on the basis of the initial photodetection data Di. In practice, photosensitive detection data for fire recognition is derived from a moving average of multiple stain-corrected data. These smear correction data are obtained at every fixed detection interval according to the master clock. When the time interval during which the number of photosensitive detections is lower than a predetermined threshold lasts for a fixed length of time, it is determined that a fire has occurred. As a result of the fire identification process at block 80, when a fire is identified in block 82, block 84 follows and a fire signal is output to the receiver. On the contrary, when it is judged that there is no fire, the fire signal output process in the frame 84 is not executed but directly enters the frame 86 and the control is stopped while the microcomputer returns to the standby state. Then, the system waits until the input of the next clock pulse.

FIG. 5 is a block diagram showing the functions of a microcomputer executing the control process in FIG. 4. Referring to FIG. The microcomputer is composed of an initial photosensitive detection data storage device 88 , a correction ratio correction device 90 , a correction counter 92 , a correction operation device 94 , and a fire recognition device 96 .

That is, the initial photosensitive detection data storage means 88 only stores the photosensitive detection data Dm as the initial photosensitive detection data Di at the time of power reset due to power on. When storing the initial photosensitive detection data, it is obviously assumed that the photosensitive detection data is within a predetermined range. Referring to the stain correction process in the flow chart of FIG. 6, the functions of the correction comparison means 90, correction counter 92 and correction arithmetic means 94 will be further clearly understood. In addition, the correction calculation unit 94 performs stain correction on the photosensitive detection data Dn obtained by the light emission and light reception control of the master clock, calculates and outputs the correction data Da, and supplies it to the fire recognition unit 96 .

Figure 6 is a flowchart showing the smear correction process. This process is performed by the photosensitive detection element in the photoelectric smoke detector of the present invention. This tarnish correction process is carried out by the program control of the microcomputer that constitutes the control unit, or by the function block that comprises correction comparison device 90 shown in FIG. implement.

The smear correction process of Fig. 6 will now be described. First in block 100 a correction counter is incremented. The correction counter can be realized by a program counter. The correction counter counts a master clock which is output for a fixed period in the range of, for example, 2.7 to 3.0 seconds, the counter reaches full count in about 50 minutes and produces a counter output to perform the stain correction process. That is, the count value of the correction counter is monitored in identification block 102 . When the counting time of the counter reaches 50 minutes as the calibration period, the calibration process in block 104 and subsequent blocks starts.

The principles of the smear correction process performed in block 104 and subsequent blocks will be described below.

Assume now that the correction ratio at this moment is N when the current photosensitive detection data obtained according to the light emission and light reception control of the clock pulse is Dn. The corrected photosensitive detection data Da will be obtained by the following formula:

Da=Dn×N...(1)

The correction ratio N in equation (1) is defined as:

N=1/(1-K/100)...(2)

Where K is a correction coefficient and K=0 in the initial state, as the photosensitive detection data decreases due to contamination, the correction coefficient K increases continuously in each correction period, such as K=1, 2, 3... On the contrary, As the photosensitive detection data increases, the correction coefficient K has a similar continuously decreasing value in each correction cycle, such as K=-1, -2, -3 . . . . That is, when the initial photosensitive detection data Di does not match the current photosensitive detection data Dn, the correction coefficient K only increases or decreases by ±1 in each correction cycle, thereby correcting the correction ratio N.

The smudge correction process in block 104 and subsequent blocks will be given a practical description. First in block 104 the correction counter is cleared. Then, the corrected photosensitive detection data Da is calculated in block 106 from the previous correction ratio Nn _-1 and the current photosensitive detection data Dn by the above equation (1).

After calculating the corrected photosensitive detection data Da in block 106, an identification block 108 is entered and a check is made to determine if the corrected photosensitive detection data Da is equal to the initial photosensitive detection data Di. At this point, if the window is not stained, Da = Di. However, if it has been soiled, the corrected photosensitive detection data Da becomes smaller than the data Di, so that the process proceeds to identification block 110 . In block 110, the magnitudes of the corrected photosensitive detection data Da and the initial photosensitive detection data Di are compared. In the identification comparison of the identification block 110, when the corrected photosensitive detection data Da is greater than the initial photosensitive detection data Di, enter the box 112 and perform correction of the correction coefficient Kn to a smaller value so as to reduce the correction ratio N Coefficient correction process. That is, when Da>Di, because the previous correction ratio N _n-1 used to calculate the corrected photosensitive detection data Da in block 106 is too large, the calculated corrected photosensitive detection data Da is greater than the initial photosensitive detection data Di. Therefore, in block 112, the recalibrated correction factor Kn is calculated by the equation determined by:

Kn=Kn _-1-1 ...(3)

On the contrary, when it is determined that Da<Di in the identification block 110, enter block 114 and the new correction coefficient Kn is calculated by the following correction formula:

Kn=Kn _-1 +1...(4)

In the case of corrections to the correction coefficients in block 114, since the previous correction ratio Nn _-1 used to calculate the corrected photosensitive detection data Da in block 106 is too large, Da<Di, there is a lack of smear correction. Therefore, a new correction coefficient Kn is obtained by increasing the correction coefficient K _n−1 by +1 by the above formula (4). This increase in Kn causes the value of the correction ratio N obtained by the above formula (2) to also be increased.

Due to one correction in blocks 112 and 114, the variation of the correction coefficient K is ±1, therefore, the variation of the correction ratio is also compressed to a tiny value.

After calculating the new correction coefficient Kn in block 112 or 114, enter the next block 116 and use the correction coefficient Kn to correct according to the above formulas (1) and (2) and then calculate the corrected photosensitive detection data Da again.

That is, when the correction of Kn= _Kn-1 ±1 is performed because Da<Di, the correction ratio N is also increased and the corrected photosensitive detection data Da which is further closer to the initial photosensitive detection data Di is calculated. On the contrary, when correction of Kn=Kn _-1-1 is performed because Da>Di, the correction ratio N is also reduced, thereby similarly calculating corrected photosensitive detection data closer to initial photosensitive detection data Di.

Then, in identification block 118, a check is made to determine whether the new correction factor Kn corrected in block 112 or 114 is within a predetermined limit.

As an embodiment, the changing range of the correction coefficient Kn is limited to one of the following ranges.

+50＞Kn＞-20...(5)

Therefore, as a result of correction of the correction coefficient Kn at each correction period, when the correction coefficient Kn reaches 50 or -20, a value of Kn is out of the range of the formula (5). In this way, it is determined that the contamination correction by signal processing cannot be performed, and the processing program enters block 120 and outputs a check alarm signal to the receiver, indicating to clean up the dirt attached to the window of the light-emitting and photosensitive detection elements.

This smear correction shown in the flow chart of Fig. 6 will be described below using actual numerical values.

Assume now that the initial photosensitive detection data is equal to 100, the photosensitive detection data obtained in the current calibration period is 95 and the previous correction coefficient K _n-1 is 0.

Correction data Da is calculated in block 106. Since the correction coefficient Kn _-1 is 0, Da is calculated to be equal to Dn=95 from the above formulas (1) and (2).

Since the corrected photosensitive detection data Da is smaller than the initial photosensitive detection data Di, block 114 is entered. In block 114, the correction coefficient is corrected by determining Kn=Kn _-1 +1=0+1=1.

Subsequently, the corrected photosensitive detection data Da is calculated using the correction coefficient Kn=1 after the correction in block 116 as follows,

Da=95×[1/(1-1/100)]=95.95

Assuming that the current photosensitive detection data obtained in the next calibration cycle is also Dn=95, the calibration coefficient Kn is corrected to 2 in block 114, and thus calculated in block 116

Da=95×[1/(1-2/100)]=96.9

Similar to the above method, the correction coefficient Kn is increased in each correction cycle, so that Kn=3, 4, 5...

In this way, the current photosensitive detection data Dn=95 is close to the initial photosensitive detection data Di, and the correction coefficient increases in each correction cycle, which makes Kn=0, 1, 2, 3, 4, 5, so that it is given by formula (2) The correction ratio N is increased such that N=1.00, 1.01, 1.02, 1.03, 1.04, 1.05. As a result, even if the current photosensitive detection data Dn is still 95, the photosensitive detection data is corrected. Da was increased such that Da = 95.00, 95.95, 96.94, 97.94, 98.96, 100.00. In this way, the corrected photosensitive detection data coincides with the initial photosensitive detection data in the fifth correction period. As long as the relationship of Da=Di is maintained, contamination correction can be accomplished by using a correction ratio N=1.05 determined by a correction coefficient Kn=5.

On the contrary, when the current photosensitive detection data Dn exceeds the initial photosensitive detection data, due to the block 112, the correction coefficient Kn is decreased in each correction cycle so that Kn=0, -1, -2, -3. Thus the correction ratio N is reduced so that N=1.00, 0.99, 0.98, 0.97..., thereby making the corrected photosensitive detection data Da approach the initial photosensitive detection data Di.

In the operation of the correction process in the actual program process, when it is assumed that the data includes, for example, eight bits, the operation process is performed by determining

256Da＝256〔Dn×1/(1-Kn/100)〕

In the flowchart of FIG. 6, the correction coefficient Kn is increased or decreased by only ±1 in each correction period. However, if the correction is changed by a ratio of N The change is a small value, and the change of the correction coefficient can be ±2, ±3,.... The change value of the correction coefficient can be determined as an arbitrary value within a range, as long as it does not exceed the change value of the photosensitive detection data in a smoky fire situation within this range.

In addition, although the present invention has been described for the extinction-type separated photoelectric smoke detector, the present invention can also be applied to an integral photoelectric smoke detector according to its actual situation, wherein the light-emitting element and the photosensitive detection element of the present invention are integrated Assembled in a box.

Claims (5)

1, photoelectric smoke sensor, one of them light-emitting component (14) and a photosensitive detection device (12) are installed toward each other and are being left a predetermined distance each other, the pulsed light that sends from above-mentioned light-emitting component weakens owing to smog and is received by above-mentioned photosensitive detection device, detect the condition of a fire thus, this photoelectric smoke sensor is characterised in that it comprises:

A storing apparatus (88), it when power connection with photosensitive detection data D _nStored regularly and be used as the quick detection data of initial light D _i:

Proofread and correct relatively equipment (90) for one, this device is at the photosensitive detection data D of each predetermined pickup calibration cycle with this moment _nWith above-mentioned initial photosensitive detection data D _iCompare, and, when producing difference between above-mentioned two data, proofread and correct a correction than N according to this difference:

A correction computing device (94), the photosensitive detection data D that its input obtains at each predetermined period that is shorter than above-mentioned calibration cycle _n, and obtain proofread and correct photosensitive detection data D as multiplier by multiplication than N with correction in this moment _a: and

A smog recognition device (96), it discerns the condition of a fire on the basis of the photosensitive detection data of above-mentioned correction.

2, according to the photoelectric smoke sensor of claim 1, wherein said correction comparison equipment only has in time of a pickup trimming process by a predetermined small value proofreading and correct than the device of proofreading and correct.

3, according to the photoelectric smoke sensor of claim 1, power supply is cut off after described initial photosensitive detection data are stored even wherein said memory storage has, still can be with the device of this an initial photosensitive detection data storage and a set time sections of maintenance.

4, according to the photoelectric smoke sensor of claim 1, wherein said memory storage has the verification of data device, this is checked device and checks to determine whether described initial photosensitive detection data are within the predetermined scope, should initial photosensitive detection data storage in the time of in it is in this scope, when these initial photosensitive detection data were outside above-mentioned scope, this was checked device and produces an alarm.

5, according to the photoelectric smoke sensor of claim 1, wherein said condition of a fire recognition device has by comparing with a threshold value from a dynamic mean of the photosensitive detection data of a plurality of corrections of above-mentioned correction computing device output discerns the device of the condition of a fire.

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