JPH0211102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas detection device using a semiconductor gas detection element, and is intended to avoid malfunctions at the initial stage of energization due to the characteristics of the semiconductor gas detection element.

A conventional example is Utility Model Application No. 50-67887, which shows curve A when electricity starts in an atmosphere where gas exists.
As long as the gas is present, the gas does not descend and does not go into a state of alarm, so the state of alarm remains inactive and cannot be distinguished from a normal state, and there is a strong risk that it may be mistaken as being in a state of alarm, which is dangerous.

The present invention was established to solve the above problems.

An overview of the present invention will be explained based on FIGS. 1, 2, and 3.

In the basic embodiment of the invention shown in FIG.
1 is a power supply, 2 is a transformer heater winding that supplies power to the heater of the gas element, 3 is a transformer winding that provides power for the control circuit, 4 is a control circuit power supply that rectifies and smoothes the output of 3, and 5 is a gas semiconductor part of the sensing element,
6, 7, 8, 9, 10, and 11 are circuits for rectifying and smoothing the output of the sensing element 5, and provide the A output in FIGS. 1 and 2. 12 and 13 are constant voltage circuits, and the constant voltage of this constant voltage circuit is divided by 14 and 15 to obtain an alarm level voltage B. A first voltage comparator 25 (the figure shows a voltage comparator using an operational amplifier; the same applies hereinafter) compares the A and B voltages, and a C output is obtained. By short-circuiting and opening both ends of the resistor 18 of the voltage divider 16, 17, and 18 using a two-stage inverting circuit consisting of C outputs 21, 22, 23, and 28, the positive potential of the output C is obtained from the connection point of 16 and 17. The output C' of the shift circuit is obtained by shifting to the side to obtain a medium potential (m) and a high potential (h). Reference numerals 19 and 20 designate charging circuits that obtain an output D that rises exponentially from the start of energization. The above C' and D are connected to the second voltage comparator 24.
Compare with and get E output. 26 and 27 are quick charging circuits for rapidly charging the battery 20 when the E output of the second ratio comparator becomes 1. 31 and 32 are AND circuits that become conductive when both the output C of the first comparator and the output E of the second comparator become 1;
indicates an alarm circuit, etc., and F is given by the output at both ends.

Next, the operating state will be explained. FIG. 1 shows the voltage waveforms of each part when energization starts in a normal atmosphere, and FIG. 2 shows the voltage waveforms of each part when energization starts in a gas atmosphere.

A is the DC gas element output voltage after rectification and smoothing.

B is a comparison voltage of alarm level voltage.

C is the 0 and 1 output voltage given by comparing A and B above.

C' is a comparison voltage that moves in correspondence with C and provides a medium level voltage (m) and a high level voltage (h).

D is a voltage that increases exponentially from the start of energization, and rapidly increases when D>C'.

E is the output voltage that changes from 0 to 1 when D>C'.

F is the AND output voltage of C and E, and indicates the voltage applied to alarm, control, etc. circuits.

In the normal case (Fig. 1) A starts to rise from the 0 time point at the start of energization, exceeds the comparison voltage B at the time point a, C goes from 0 to 1, and C' goes from medium potential m to high potential h. At this point, the setting is such that C'>D is maintained. On the other hand, D increases from point 0. At point b when A decreases and becomes smaller than B, C changes from 1 to 0, C' changes from h to m, D>C', and E changes from 0 to 1 when comparing D and C'. E is 1
When D rises rapidly and exceeds the h level of C', E remains at 1 even if C' reaches the h level. When gas is detected and A>B at time C, C becomes 1. AND output F of C and E becomes 0 → 1,
Alarm circuits etc. operate. As the gas detection output decreases, A<B and C becomes 0 at time d. The AND output F of C and E changes from 1 to 0, and the alarm etc. stops.

In the case of an abnormality, A starts to rise from the 0 time point at the start of energization, exceeds the comparison voltage B at the time point a, C goes from 0 to 1, and C' goes from m to h. On the other hand, D increases from point 0. Since the state of A>B continues, C and C' do not change and only D continues to rise, and at time b, D>C' and E becomes 1.
With this output, D continues to rise rapidly and thereafter maintains D>C'. The AND output F of C and E becomes 1, and the alarm etc. continues to be emitted.

As described above, in addition to avoiding initial malfunctions during normal operation, even if electricity is started in a gas atmosphere, an abnormality can be detected after time b, eliminating the dangerous situation that occurs in conventional cases. This is extremely effective in practice.

Next, an application example of the present invention shown in FIG. 4 will be explained.

In FIG. 3 of the previous explanation, from the time of starting energization, b
Up to this point (see Figure 2), this device is not in a state to be alert for gas, so in practical terms, b
This was done out of necessity, as it may be necessary to distinguish it from the gas warning state after that point.

36, 37, 38, 39, 40, and 41 are pulse generation circuits using operational amplifiers, and 36 is connected to the power source 4. 35 has a current limiting resistor 34 as its base.
is connected to the E output via
When , the pulse generator is generating pulses with the collector and emitter open, and E is 1.
In this case, both ends of the capacitor 41 are short-circuited to stop the pulse generation operation, and its output becomes 1. 43 is an LED that is lit by the output of the pulse generator. Therefore, in Figure 2, until E is 0, that is, 0→b,
The LED blinks, and after E is 1, that is, point b, the LED remains lit, making it possible to distinguish between them.

Next, the application example FIG. 5 will be explained. This is 0
Between b and b (see Figure 2), the LED blinks; between b and c, the LED remains lit; and between c and d, the LED blinks and an alarm flashes at the same time. The process is exactly the same as in Fig. 3 until the E and C outputs are obtained. Controlling the pulse generation circuit with the E output is the same as in FIG. 4. E
Transistor 3 whose output controls the pulse generation circuit
The base and emitter of 2 are short-circuited by 31 when the C output is 1, and are opened when the C output is 0.

accordingly Between 0 and a, LED blinks when C=0, E=0 Between a and b, C=1, E=0 Between b and c, LED lights up when C=0 and E=1 Between c and d, LED blinks when C=1, E=1 becomes.

46 is a circuit that short-circuits the collector and emitter when E=1, and enables an alarm after time b.
43 and 45 are two-stage inverting circuits, and when the output of the pulse generation circuit is connected to 1, no voltage is applied to the alarm, etc., and when the pulse output is 0 among the repeating pulse outputs of 1 and 0, the voltage is applied to the alarm, etc. join.

Therefore, up to time b, E = 0 and 46 is in the open state, so there is no alarm output, and after time b, E = 1, the alarm becomes possible, and the alarm, etc. flashes between C and a. Output is added.

Next, a description will be given of an application example shown in FIG. 6, which is combined with the detection device having the anti-time characteristic shown in the previous application. The difference from the above-mentioned Fig. 5 is that 44, 45, 46, 47, 48,
49, 50 and a voltage comparator 52 are added.

C is inverted from the output shown in FIGS. 1, 2, 3, and 5. That is, between 0 and a, C=1, between a and b, C=0, between b and c, C=1, and between c and d, C=0. Therefore, the short-circuit between both ends of the resistor 18 for obtaining C' is one stage of an inverting circuit formed by the transistor 21.

When C changes from 1 to 0, the charge at 46 is discharged through 48, 49, and 50, and the potential G at the connection point between 49 and 50 decreases exponentially. When G becomes smaller than A, the output of 52 becomes 1, short-circuits 28, generates a pulse, and applies voltage to an alarm, etc. In other words, when A is large (high concentration gas), G has to fall slightly and 52 becomes 1, and the time required for operation is short, and when A is small (low concentration gas), G must fall significantly. Therefore, it takes a long time to operate, giving it an inverse time-limiting characteristic. Other actions are 5th
Same as the figure.

As explained above, the present invention is designed to avoid the initial malfunction of electricity in a normal atmosphere, and to output an alarm etc. after a certain period of time in a gas atmosphere.
In addition to being safe for practical use, it also has the advantage of displaying a display indicating that the malfunction avoidance period is in progress, and of being easily applied to counter-timed gas detection devices.

[Brief explanation of drawings]

The drawing shows an embodiment of the gas detection device of the present invention,
FIGS. 1 to 2 are characteristic diagrams, and FIGS. 3 to 6 are electrical circuit diagrams showing embodiments of the present invention.

Claims (1)

[Claims] 1. A semiconductor gas detection element, a first comparator that compares the output A of the semiconductor gas detection element with an alarm level voltage B, and a potential positive of the output C of the first comparator. Output C that shifts to the potential side and obtains medium and high potentials
a shift circuit, a charging circuit that outputs a voltage that increases exponentially from the point of start of energization, an output D of this charging voltage circuit, and an output of the shift circuit of the output C.
a second comparator that compares C' with C'; and when the output E of this second comparator is inverted, the output D of the charging circuit is suddenly changed and the output E of the second comparator is inverted; a quick charging circuit for holding the output C of the first comparator and the output E of the second comparator;
A gas detection device characterized by comprising an AND circuit that obtains an AND output, and an alarm circuit that is activated by the output of the AND circuit. 2. In 1, the period from the start of energization until the output E of the second comparator circuit is inverted and after it is inverted.
2. The gas detection device according to item 1, characterized in that different displays are displayed using display means such as LEDs, so that malfunction avoidance time and gas warning time can be distinguished.