JPS6336457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic calibration circuit for a smoke transmittance measuring device that optically measures the transmittance of smoke, fog, etc.

Several types of smoke transmittance measurement devices have been proposed and implemented in the past, but some of them may be able to measure the true transmittance at the time of installation, but after a certain period of time, the Moreover, the amount of light received decreases due to dirt on the optical system of the light receiver and aging of the light source, light receiving element, etc., and measurement errors increase. In addition, in order to compensate for the decrease in the amount of light received, some improvements have been made, such as storing the highest value of the amount of light received and periodically performing additions and subtractions, but in recent years, illegal radio communication A phenomenon in which the amount of light received abnormally increases due to induction etc. occurs, and these improvements have the disadvantage of having the opposite effect.

The present invention automatically calibrates against a decrease in the amount of light received due to aging, and also prevents meaningless automatic calibration against an abnormal increase in the amount of light received due to the induction of illegal radio communications, etc. Accordingly, it is an object of the present invention to provide a smoke transmittance measuring device that can measure true transmittance over a long period of time.

Hereinafter, the present invention will be explained with reference to the drawings. 1st
In the figure, 1 is a light projector, and 2 is a light receiver installed at a certain distance from the light projector 1, which receives the amount of light arriving from the light projector 1 and converts it into an electrical signal corresponding to transmittance. 3 is an arithmetic unit that multiplies or divides the signal from the light receiver 2 by a correction value; if the correction value is "zero", the amount of received light directly becomes the transmittance.
4 is a first comparator that compares the value when the transmittance is 100% and the output value from the calculator 3; 5 is the value when the transmittance is 97% and the output value from the calculator 3; A second comparator 6 compares the first comparator 4 with
Continuation checker 7 confirms whether the judgment output of the second comparator 5 continues for a certain period of time (continuation time limits A and B). Continuation confirmation time C) Continuation checker below the specified value to check whether to continue or not, 8 is an up-down device that outputs a command to multiply or divide the transmittance by a certain correction value based on the output of the continuation checkers 6 and 7. Counter 9 is a 100% limiter.

Furthermore, assuming that the specified value of the second comparator 5 is 97%, the meaning of the assumption is that the confirmation time limit C of the continuation checker 7 below the specified value is assumed to be 97%.
This is related to the assumption that 7 days, but it is based on empirical results that the outdoor fog transmittance and the smoke transmittance inside the tunnel always show values close to 100% once a week. ing. However, the present invention is not necessarily restricted to the above assumed numerical values.

In the above configuration, the transmittance calibration operation is performed in the second
To explain with reference to the figure, first, the amount of light received by the emitter 1 and the receiver 2 decreases due to aging, and the transmittance continues to be below the specified value of 97% of the second comparator 5 and continues to be below the specified value. If the confirmation time limit C (7 days) of the confirmation device 7 has passed, or conversely, if 97% has never been exceeded for 7 days, the confirmation command continues to be below the specified value. 8, and the up-down counter 8 outputs an up command to the arithmetic unit 3. As a result, the arithmetic unit 3 adds a certain correction value (1+ΔT/100) to the electric signal indicating the transmittance according to the amount of light arriving from the projector 1. That is, the electric signal output from the light receiver 2 is increased by ΔT% by the calculator 3.

On the other hand, the transmittance is 100% of the specified value of the first comparator 4.
The above continues to exceed the specified value Confirmation time limit A (7) of the confirmation device 6
seconds), the confirmation command continues to exceed the specified value from the confirmation device 6 to the up-down counter 8.
The up-down counter 8 outputs a down command to the arithmetic unit 3. As a result, the calculator 3 divides the electrical signal indicating the transmittance according to the amount of light arriving from the projector 1 by a certain correction value (1+ΔT/100). That is, the electric signal output from the light receiver 2 is reduced by ΔT% by the calculator 3. Furthermore, when the output of the light receiver 2 abnormally increases due to the induction of illegal radio communication, the output of the arithmetic unit 3 continues to be 100% or more as shown in FIG. 2 even after division. This is because the computing unit 3 has a maximum limit output value, and even if the output of the light receiver 2 increases abnormally, the output of the computing unit 3 remains at the maximum limit output value, and a down command is input to the computing unit 3. Therefore, even if you divide the electric signal from the receiver by a certain correction value (1+ΔT/100), it will still exceed the maximum limit output value, and the output of the calculator 3 will remain at the maximum limit output value, as shown in Figure 2. As shown, the transmittance is as if it were unchanged. Furthermore, although the transmittance continues to be over 100%,
If the illegal radio wave communication is stopped before the confirmation time limit B (5 minutes) of the confirmation device 6 has elapsed, the state in which the above-mentioned division is performed is maintained in the arithmetic unit 3. Division is performed on the normal electrical signal, and the output (transmittance) of the arithmetic unit 3 becomes 97% or less (100% or less) as shown in FIG.
Then, the output from the predetermined value or more continuation checker 6 to the up-down counter 8 changes, and the up-down counter 8 outputs an up command to the calculator 3.
In this case, the electrical signal from the light receiver 2 is divided by a fixed correction value, and then a fixed correction value is multiplied. In other words, the arithmetic unit receives the input light receiver 2.
Outputs the electrical signal as is.

As is clear from the above description, the present invention automatically calibrates the apparent decrease in the amount of light received due to dirt in the optical systems of the emitter and receiver, as well as changes over time, and further reduces the amount of light received by guiding illegal radio waves. It is possible to prevent meaningless automatic calibration even in the case of an abnormal rise, and it is possible to accurately measure transmittance over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an automatic calibration circuit for a smoke transmittance measuring device according to the present invention, and FIG. 2 is a time chart showing the operation of the circuit. 1... Emitter, 2... Light receiver, 3... Arithmetic unit,
4, 5... Comparator, 6... Continuation confirmation device above the specified value, 7... Continuation confirmation device below the specified value, 8... Up-down counter.

Claims (1)

[Claims] 1. A light receiver that is installed at a certain distance from the light emitter and converts it into an electrical signal indicating a transmittance according to the amount of light arriving from the light emitter, and a signal from the light receiver that is multiplied or divided by a certain correction value. an arithmetic unit; a first comparator that compares a value when the transmittance is 100% with an output value of the arithmetic unit; and a predetermined value and the arithmetic operation when the transmittance is a predetermined transmittance smaller than 100%; A second computing unit compares the output value of the computing unit with the output value of the computing unit, and the first comparator compares the output value of the computing unit with the transmittance of 100.
%, a first output is output when the output is greater than the value of % for a first predetermined period of time or more, and the first comparator determines that the output value of the arithmetic unit is equal to the transmittance.
a predetermined value or more continuation checker that outputs a second output when the output greater than the value at 100% changes within a second predetermined time period that is longer than the first predetermined time period; a continuation checker that outputs a third output when the output value of the arithmetic unit is smaller than the specified value at the predetermined transmittance continues for a third predetermined time; 2 output and a third output are input, and when the first output is input, a down command is outputted to the arithmetic unit to perform the division, and the second output is input.
An automatic calibration circuit for a smoke transmittance measuring device, comprising an up-down counter that outputs an up command for causing the arithmetic unit to perform the remainder calculation when the output or the third output is input.