SU1486827A1 - Device for detecting gas leaks - Google Patents

Description

The invention relates to measuring technique and allows to increase the sensitivity and accuracy

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determining gas concentration by compensating for drift. A device for detecting gas leaks contains a power source 1, a gas sensor 2, a threshold circuit 3, a frequency divider 5, a step signal generator 6, a comparison circuit 7, a memory register 8, AND 9.10 and 11 circuits, and light and sound blocks 12 and 13 alarms.

When the device is periodically compared by the circuit 7 comparison of the codes of the operating mode and stored in the H register 8 memory. The gas concentration is determined by the duration of the output signal of the blocks 12 and 13 of the light and sound alarm. 1 hp f-ly, 1 ill.

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The invention relates to measuring technique and can be used to determine the concentration of hydrocarbon gases $ when monitoring the tightness of products ^

The purpose of the invention is to increase the sensitivity and accuracy of determining the concentration of gas by compensating for the drift.

The drawing shows a block diagram of the proposed device ·.

The device contains series-connected power source 1 and gas sensor 2, threshold circuit 3, the first input of which is connected to the output of gas sensor 2, the reference voltage source 4, the input of which is connected to the second output of power supply 1, and the output 'to the second the input of the threshold 20 of the circuit 3, the frequency divider 5, the generator 6 of the step signal, the first input of which is connected to the output of the gas sensor 2 and the first input of the threshold ₍ circuit 3, and the first output is connected to the 25 output of the reference voltage source 4 and the second input of the threshold circuit 3, circuit 7 comparison, the first input of which is connected to the second generator output 6 of the step signal, memory register 8, the first input of which is connected to the second output of the generator 6 of the step signal and the first input of the comparison circuit 7, and the second to the second input of the comparison circuit 7, the first circuit And 9, the first ^ 5 input of which is connected to the output of the threshold circuit 3, the second - to the first output of the comparison circuit 7, and the output to the second input of the generator is 6 steps, _n 40

signal, the second circuit And 10, the first input of which is connected to the output of the threshold circuit 3, the second - with the second output of the comparison circuit 7, and the output - with the second input of the memory register 8, the third circuit And 11, the first input of which is connected to the output of the threshold circuit 3, the second with the third output of the comparison circuit 7, and the output with the first input of the frequency divider 5, the input of the light signaling unit 12 and the input-5θ house of the sound alarm 13, the output of which is connected to the second input of the frequency divider 5, the output of which connected to the third input of the 6-speed generator signal. 55

The device works as follows.

When the power is turned on, heating and setting of the gas sensor 2 mode occurs. The initial setup signal (not shown) of the 6-step signal generator and the memory register 8 are set to the initial state and the light and sound alarm blocks 12 and 13 are turned on, which indicates the health of the alarm blocks 12 and 13 and the gas sensor 2. The duration of the initial setup signal is determined by the time when the gas sensor reaches the operating mode, 2 gas and is equal to 5-10 s. At the first input of the threshold circuit 3, the voltage is greater than the second, which leads to the establishment of a zero signal at the output of the threshold circuit 3. After passing the initial setup pulse, the 6-step signal generator starts counting pulses from the output of frequency divider 5 and produces a stepwise sawtooth voltage, which is summed with the reference signal at the second input of the threshold circuit 3. The magnitude of the reference signal from the output of the reference voltage source 4 varies in accordance with the change in operating current d gas 2 in such a way as to compensate for the resulting drift in the operating mode of the gas sensor 2. The gas sensitivity of the device is determined by the amplitude value of the "step" from the generator output 6 of the step signal, which also changes in accordance with the sensitivity change that occurs when the power supply voltage decreases. The sensitivity is corrected through the first control input of the generator of the 6-speed signal.

Each "step" of the signal at the analog output of the 6-step signal generator corresponds to a digital code at the code output that goes to the first inputs A of the comparison circuit 7 and the memory register 8. To the second input of the circuit 7 comparison receives the digital code from the output of the register 8 memory. The result of the comparison of the two codes is set at the output of the comparison circuit 7. When the sum of voltages from the output of the generator 6 of the stepped signal and the source 4 of the reference voltage becomes greater than the voltage at the output of the gas sensor 2, the threshold value is 1486827

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Scheme 3 is set to one and allows reading of the comparison result.

Since, under the action of the initial setup signal, the memory register 8 stores the initial state, and the 6-step signal generator counted a certain number of pulses, the code on the first output of the comparison circuit 7 will be larger than on the second. The output signal of the comparison circuit 7 through the AND 10 V circuit Register 8 of memory is recorded a new digital code present at its input, which will lead 15 to the equality of the codes at the inputs of the comparison circuit 7. The signal from the output of the circuit 7. comparison through the circuit And 9 generator 6 speed signal will be restored to its original state. At 20, this threshold circuit 3 will be established in the original zero state, and the circuit And 9-11 will be closed. Register 8 memory will store the recorded digital code. If the voltage at the output of the gas sensor 2 has not reached the steady-state value and continues to increase, then the above-described operation of writing the new code to the memory register 8 will be repeated. ₃₀

In the steady state, the voltage on the gas sensor 2 in the absence of gas does not change and the result of comparing the codes when switching the threshold circuit 3 to one state will produce an output signal from the equality of codes on the inputs of the comparison circuit 7, which will set the generator 6 speed signal to its original state. The operation of tracking the voltage output from the gas sensor 2 will be repeated. The tracking frequency when there is no signal at the control output of the sound alarm unit 13 is determined by the frequency of the 45 clock generator in the sound alarm unit 13 and is set based on the response time of the sensor 2 to gas in the range from 5 to 1 (7 Hz. When a signal appears at the ςθ input control unit 13 audible alarm and the frequency of the clock generator is increased to the limits of the sound range and is set based on the optimal radiation of the microphone in the range from 1 to 3 kHz. · Since the work at the sound frequency It takes a much smaller part of the time of the entire operation of the device, this allows you to more fully use the battery by reducing the switching frequency of the elements used in the K561 series and a corresponding reduction in the current consumed by them When the gas sensor 2 is introduced into the zone with steady gas concentration, the output gas gas 2 will decrease in proportion to the gas concentration value and when the generator generates the 6-step signal of the output voltage of the gas sensor 2 (as a result of comparing the kodo a code output step signal generator 6 and 8 memory register) at the output of comparator 7 will be a signal which, via the AND circuit 11 will allow operation units 13 and 12, an audible and visual alarm. ,

The appearance of the signal at the control input of the sound alarm unit 13 leads to an increase in the frequency of the internal clock generator and to the appearance of a sound signal. The increase in the frequency at the output of the divider 5 frequency is compensated by an increase in the division factor when the signal from the output of the AND 11 circuit arrives at the control input of the divider 5.

At the same time, the 6-step signal generator continues counting pulses from the output of frequency divider 5.

At the moment of establishing equality of codes from the generator output 6 of the step signal and the output of the register 8 memory, a signal will appear at the output of the comparison circuit 7, which will set the generator 6 of the step signal to the initial state and the tracking operation will repeat. At the same time, with an increase in the concentration of the measured gas, the time between the appearance of signals in A <B and A-B at the outputs of the comparison circuit increases, and the operation time of the sound and light alarm units 13 and 12 increases accordingly. The location with the highest gas concentration, i.e. the place of its leakage. Testing the prototype of the device showed that the proposed device compared to the prototype has a higher sensitivity, independent of the duration of the measurements, which allows partial compensation.

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changes in sensitivity from changes in supply voltage, in addition, the dynamic range for gas is determined only by the capabilities of gas sensor 2, which reduces the non-linearity of the output signal of gas sensor 2 as a function of gas concentration and simplifies the process of determining the maximum gas concentration light and sound alarm.

The use of the proposed device improves the reliability of determining 15 the gas concentration value and simplifies the search for gas leakage into the product. In addition, the device allows, if necessary, to increase the digit capacity of the digital code and, accordingly, to increase the gas sensitivity of the device, as well as to make a digital indication of the gas concentration value when the device is supplemented with a decoder counter. 25

Claims (2)

Claim 1. A device for detecting gas leaks, containing in series 30 a power source and a gas sensor, a threshold circuit whose input is connected to the gas sensor output, a memory register and a light signaling unit, characterized in that, in order to increase the sensitivity and accuracy of determining the gas concentration , it is equipped with a reference voltage source, a step signal generator, a comparison circuit, a frequency divider and first, second and third I circuits, the first inputs of which are connected to the output of the threshold circuit, the first input which is connected to the output of the gas sensor and the first input of the step signal generator, and the second to the output of the reference voltage source, the input of which is connected to the output of the power source, and the output to the first output of the step signal generator, the second output of which is connected to the first inputs of the circuit comparison and memory register, the output of which is connected to the second input of the comparison circuit, the first, second and third outputs of which are respectively connected to the second inputs of the first, second and third circuits And, the output of the first circuit And connected to the second input of the step signal generator, the output of the second And circuit with the second input of the memory register, and the output of the third And circuit with the first input of the frequency divider and the input of the light signaling unit, and the output of the frequency divider connected to the third input of the step signal generator. ι 2. The device, according to claim 1, about the t i l and th e s with the fact that, in order to increase reliability, it is equipped with a sound alarm unit, the input of which is connected to the second output of the third And circuit and the first input of the frequency divider, the second input of which is connected to the output of the audio alarm unit.