RU2029291C1 - Photocalorimetric gas analyzer - Google Patents

Abstract

FIELD: analytical devices. SUBSTANCE: photocalorimetric gas analyzer has a signal time discriminator; series-connected first comparator with controllable comparison signal threshold level, weight pulse integrator with controllable integration time, first synchronous adder of signal pulse amplitudes and first controllable amplifier; series-connected first pulse integrator with controllable integration time, second controllable amplifier and first inverter; series-connected switch, first unit for square-law conversion of amplitudes of signals, second pulse integrator with controllable integration time, third controllable amplifier and second synchronous adder of amplitudes of signals, third pulse integrator with controllable integration time, second unit for square-law conversion of amplitudes of signals and second inverter, third unit for square-law conversion of amplitudes of signals and second comparator with controllable comparison signal threshold level, first pulse counter and first control threshold element, second pulse counter, control unit for control of the first comparator threshold level, second threshold element and OR gate. EFFECT: enhanced reliability. 1 dwg

Description

 The invention relates to analytical devices for measuring the concentration of harmful substances in the air, based on measuring changes in the optical properties of the surface of the gas-sensitive element under the influence of the analyzed medium and can be used in various industries.

 Known photocolorimetric gas analyzer containing a photoblock with a source and a receiver of radiation, a gas sensor with a tape drive and its drive, time relay, amplifiers, switch, adder, pulse counter, recording device [1].

 The disadvantages of this photocolorimetric gas analyzer are insufficient reliability and accuracy of measurement, as well as insufficient automation, which requires the use of a timer in the gas analyzer for its periodic inclusion.

 Closest to the invention in technical essence is a photocolorimetric gas analyzer containing a photoblock with a radiation source and receiver, a gas sensitive indicator means, a pulse counter, a command device, a switch, a recording device [2].

 The disadvantages of this gas analyzer are insufficient measurement accuracy, as well as insufficient automation.

 These shortcomings lead to the irrational use of the "machine" time of the gas analyzer.

 The aim of the invention is to reduce the measurement time by automating the measurement process while increasing the accuracy of the measurements.

 The goal is achieved in that the photocolorimetric gas analyzer, including a photoblock with a radiation source and receiver, an indicator tape element optically connected to the photoblock, a tape drive with a step drive kinematically connected to the tape element, a software device, a comparator, a recording device, is equipped with a time signal sampling device connected in series by a first comparator with an adjustable threshold level of a comparison signal, a weighted pulse integrator with an adjustable time integration, the first synchronous signal pulse amplitude amplitude adder and the first adjustable amplifier, connected in series by the first pulse integrator with adjustable integration time, the second adjustable amplifier and the first inverter, connected in series with the key, the first quadratic signal amplitude conversion unit, the second pulse integrator with adjustable integration time, the third adjustable amplifier and a second synchronous adder of signal amplitudes, connected in series by a third impulse integrator with an adjustable integration time, a second quadratic signal amplitude conversion unit and a second inverter connected in series with a third quadratic signal amplitude conversion unit and a second comparator with an adjustable comparison signal threshold level, connected in series with a first pulse counter and a first control threshold element, a second counter pulses, the threshold level control unit of the first comparator, the second threshold element with OR and OR circuit, while the input of the signal sampler is connected in time to the output of the radiation detector of the photoblock, the first output of the sampler is connected to the working input of the key and the input of the first comparator with an adjustable threshold level of the comparison signal, and the second output is connected to the counting input of the first pulse counter, output the first control threshold element is connected to the first input of the counter and to the first control input of the key, the output of which is connected to the input of the third pulse integrator with an adjustable integration time, the output of the second inverter is connected to the second input of the second synchronous pulse signal amplitude adder, the output of which is connected to the first input of the software device, the second input of which is connected to the input of the second threshold element, which controls the input of the weight integrator and the output of the second pulse counter, the counting input of which is connected to the first input zeroing the control unit by the threshold level of the comparison signal and the second output of the first comparator, the input of the control of the set threshold level of the comparison signals to The second one is connected to the output of the control unit by the threshold level of the comparison signal, the control inputs of the first and second amplifiers are connected respectively to the first and second outputs of the software device, the third output of which is connected to the control input of the set threshold level of the comparison signal of the second comparator, the output of which is connected to the first input of the OR circuit , the second input of which is connected to the output of the second threshold element, the output of the OR circuit is connected to the second control input of the key, with the control input of the step drive m of a tape drive mechanism, with an input for setting a threshold of a control unit for a threshold level of a comparator comparison signal and with inputs for zeroing a software device, first and second pulse counters, second and third pulse integrators with adjustable integration time, weight integrator and first pulse integrator with adjustable integration time, input which is connected to the first output of the first comparator, the third output of which is connected to the first control input of the key, the input registering Ora is connected to the output of the first controlled amplifier, the output of the first inverter is connected to the second input of the first synchronous adder of signal amplitudes, the output of which is connected to the input of the third block of quadratic conversion of signal amplitudes, the output of the first counter is connected to the control input of the third amplifier and the third input of the software device.

 The essence of the proposed technical solution lies in the fact that the error is significantly reduced due to the optimal accumulation of information during the measurements, automatic change of the "frame" of the gas-sensitive tape indicator element at the moment of achieving the specified measurement accuracy, and thus the rational use of the "machine" time of the gas analyzer, is ensured.

 Known technical solutions characterized by the proposed combination of features and allowing to increase the accuracy of measurements and automation of measurements have not been identified, which allows us to draw conclusions about the novelty, significant differences and the achieved technical level of the proposed technical solution.

 The drawing shows a functional diagram of the proposed photocolorimetric gas analyzer, which includes a photoblock 1 with a source and a radiation receiver, an indicator tape element 2, optically coupled to a photoblock 1, a tape drive 3 with a step drive, kinematically connected with a tape element 2, a software device 4 having three working inputs, zeroing input to return the software device to its original position and three outputs and designed to control the parameters of the gas analyzer blocks, not a high comparator 5 with an adjustable threshold level of the comparison signal, having two inputs and three outputs, a recording device 6 calibrated in units of harmful gas concentration, a sampler 7, having an input and two outputs, designed to convert an analog signal to a pulse, "weight" integrator 8 pulses with adjustable integration time, having a working input, a control input, a zero signal input and one output, a first synchronous adder 9 having two inputs and one output, a first adjustable amplifier 10 having working and controlling inputs and outputs, a first pulse integrator 11 with adjustable integration time, having a working input, a zeroing signal input and output, a second adjustable amplifier 12 having working and control inputs and an output, a first inverter 13 having an input and an output, a key 14 having working and control inputs, input of zeroing signal and output, first block 15 of quadratic transformation of signal amplitude, having input and output, second pulse integrator 16 with adjustable integration time, having working input, input signal and zeroing and output, the third adjustable amplifier 17 having operating and control inputs and output, the second synchronous adder 18 having two inputs and one output, the third pulse integrator 19 with adjustable integration time, having a working input, zeroing signal input and output, the second a unit 20 for quadratic transformation of the signal amplitude having an input and an output, a second inverter 21 having an input and an output, a third unit 22 for a quadratic transformation of a signal amplitude having an input and an output, a second comparator 23 with an adjustable threshold level with comparison channel having two inputs and three outputs, a first counter 24 pulses having a working input, a control input, a zero signal input and an output, a first control threshold element 25 having an input and an output, a second pulse counter 26 having a working input, a signal input zeroing and output, the threshold level signal control unit 27 of the first comparator having a working input, a zeroing signal input and output, a second threshold element 28 having an input and output, OR circuit 29 with two inputs and one output.

 Photocolorimetric gas analyzer operates as follows.

 During one concentration measurement cycle, the gas analyzer is automatically alternately in the "threshold determination" signal level (when exceeded, a transition to a new concentration measurement cycle is performed), "memory" and "measurement", determined by software device 4.

 In the "threshold determination" mode, the signals are processed in blocks 16-21 and 4, the measured threshold value is stored in the software device 4. In the "measurement" mode, the signals are processed in blocks 6.8-13,22,23,28,29.

When the indicator tape element 2 is illuminated by the light flux from the photoblock 1, the reflected light flux enters the radiation receiver of the photoblock 1, the output signals of which are sampled in time by a sampler 7 with a repetition period T _p (converted into periodic pulse signals).

 Each concentration measurement cycle begins with the "threshold determination" mode with the key 14. After a quadratic transformation of the signal amplitudes in block 15, they are integrated (time-summed) by the inverter 16 and amplified by an amplifier 17 with an adjustable gain equal to K and set by a counter of 24 pulses ( To - the contents of the counter 24, the number of received pulses). In the integrator 19, the signals are integrated (summed over time), after which a quadratic transformation of their amplitude is performed in block 20 and inverted by an inverter 21 (change of sign of the amplitudes).

J $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ -

J

где J_i - амплитуда i-го импульса.After synchronously summing the amplitudes of the signals in the adder 18 from the amplifier 17 and the inverter 21, the amplitude is formed
A = k

J $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ -

J

where J _i is the amplitude of the i-th pulse.

 Amplitude A is stored in software device 4.

The completion of the blocks 16-21 is performed by closing the key 14. The key 14 is closed by the control threshold element 25 or the comparator 5 with an adjustable threshold level of the comparison signal. By element 25, the key is closed if the contents of counter 24 reaches a predetermined value of the m (m + 1) th pulse, etc. are not allowed on blocks 16-21). The key 14 is also closed if the amplitudes of the signals at the input of the comparator 5 exceed the threshold value J _about . Such a closure occurs if the time interval ΔТ from the beginning of the measurement cycle to exceeding the threshold value J _о satisfies the condition ΔТ <mT _n . After closing the key 14, the operation of the counter 24 stops (the contents of the counter 24 is fixed) until the next measurement cycle. The termination of its work is performed by element 25 and the comparator 5. The contents of the counter 24, including at the time of completion of its work, is transmitted to the software device 4.

After exceeding in the comparator 5 the amplitude of the signals of the threshold value J _о , the operation of blocks 6, 8-13, 22, 23, 28, 29 starts, and the pulse counter 26 is turned on and the threshold value control unit 27 sets the threshold value to zero.

и вычисляемым в программном
устройстве 4 (N - содержимое счетчика 26) и инвертируются в инверторе 13. В сумматоре 9 производится синхронное суммирование амплитуд сигналов, поступающих с интегратора 8 и инвертора 13.In integrator 8, weight integration (time summation) of pulse amplitudes is performed with weights equal to the contents of counter 26. In integrator 11, integration (time summation) of signal amplitudes is performed, after which they are amplified by amplifier 12 with an adjustable gain equal to

and computed in software
device 4 (N - the contents of the counter 26) and are inverted in the inverter 13. In the adder 9 is a synchronous summation of the amplitudes of the signals coming from the integrator 8 and the inverter 13.

iJ_i-

J_i
Просуммированные в сумматоре 9, амплитуды сигналов, начиная с N = 2, подаются в усилитель 10, в котором усиливаются, с регулируемым коэффициентом усиления, равным κ[N(N² - 1)]^-1 и вычисляемым в программном устройстве 4 ( κ- калибровочная константа), и подаются на регистрирующий прибор 6. Кроме того, просуммированные в сумматоре 9 сигналы после квадратичного преобразования в блоке 22 сравниваются в компараторе 23 с пороговым уровнем, задаваемым с программного устройства и равным

где n - содержимое счетчика 24 в момент закрытия ключа 14 (количество импульсов, прошедших обработку в блоках 16-22); γ_o=

γ- заданное среднеквадратическое отклонение относительной погрешности измерения концентрации, %.At the output of this adder, an amplitude is formed
A _o =

iJ _i -

J _i
Summed in the adder 9, the signal amplitudes, starting with N = 2, are supplied to the amplifier 10, in which they are amplified, with an adjustable gain equal to κ [N (N ² - 1)] ^-1 and calculated in the software device 4 (κ- calibration constant), and fed to the recording device 6. In addition, the signals summed in the adder 9 after quadratic conversion in block 22 are compared in the comparator 23 with a threshold level set from the software device and equal to

where n is the contents of the counter 24 at the time of closing of the key 14 (the number of pulses that have been processed in blocks 16-22); γ _o =

γ is the set standard deviation of the relative measurement error of the concentration,%.

After the threshold is exceeded, the fact of exceeding is transmitted to the OR 29 circuit. The fact of exceeding the threshold in the threshold element 28 when the condition N> N _о is met (N _o is the maximum allowable number of pulses in the concentration measurement interval) is input to the OR circuit 29.

When the circuit OR 29 is issued, a command is issued to the tape drive mechanism 3 in order to switch to the first cycle of concentration measurement. In this case, the counters 24, 26 and the integrators 16, 19, 8, 11 are reset, through the block 27, the threshold J _{о is set} in the comparator 5 and a signal is sent to the software device 4 about the completion of the concentration measurement cycle.

The given description of the gas analyzer operation refers to the case of an indicator tape brightening in the presence of a harmful substance, when the amplitude of the signals coming from the photoblock 1 increases with time. In the case of an indicator tape darkening in the presence of a harmful substance, there is a difference only in comparator 5 (signals are supplied to integrators 8 and 11 provided that the threshold value J _{о is} not exceeded) and block 27 (instead of the threshold value equal to zero, an arbitrary large value is set according to at least significantly larger than J _o ).

 Tests of the proposed photocolorimetric gas analyzer were conducted when measuring the concentration of harmful substances (gases) in the air. The relative error in measuring the concentration of ammonia in the air was 3-5%.

 In known gas analyzers, in accordance with the requirements of the State Standard, the relative error is 25%. In addition, the achieved measurement automation has increased the efficiency of using the "machine" time of a photocolorimetric gas analyzer.

 Thus, the proposed photocolorimetric gas analyzer has a higher measurement accuracy, is automated.

Claims (1)

 A PHOTOCOLORIMETRIC GAS ANALYZER containing a photoblock with a radiation source and receiver, an indicator ribbon element optically coupled to a photoblock, a tape drive with a step drive kinematically connected with a ribbon element, a software device, a comparator, a recording device, characterized in that it is equipped with a time signal sampler connected in series with a first comparator with an adjustable threshold level of a comparison signal, a weighted pulse integrator with an adjustable time, and integration, the first synchronous summation of the amplitudes of the signal pulses and the first adjustable amplifier, connected in series with the first pulse integrator with adjustable integration time, the second adjustable amplifier and the first inverter, connected in series with the key, the first unit of the quadratic transformation of the signal amplitude, the second pulse integrator with adjustable integration time, the third an adjustable amplifier and a second synchronous adder of signal amplitudes, connected in series the third pulse integrator with adjustable integration time, the second block of the quadratic transformation of the signal amplitude and the second inverter, connected in series with the third block of the quadratic conversion of the signal amplitude and the second comparator with an adjustable threshold level of the comparison signal, connected in series with the first pulse counter and the first control threshold element, the second counter pulses, the threshold level control unit of the first comparator, the second threshold element volume and OR circuit, while the input of the signal sampler is connected in time to the output of the radiation detector of the photoblock, the first output of the sampler is connected to the working input of the key and the input of the first comparator with an adjustable threshold level of comparison signals, and the second output is to the counting input of the first pulse counter, output the first control threshold element is connected to the first input of the counter and to the first control input of the key, the output of which is also connected to the input of the third pulse integrator with an adjustable integration time The output of the second inverter is connected to the second input of the second synchronous pulse signal amplitude adder, the output of which is connected to the first input of the software device, the second input of which is connected to the input of the second threshold element, which controls the input of the weight integrator and the output of the second pulse counter, the counting input of which is connected to the first input of zeroing the control unit by the threshold level of the comparison signal and to the second output of the first comparator, the input of the control of the set threshold level of signals of comp which is connected to the output of the control unit by the threshold level of the comparison signal, the control inputs of the first and second amplifiers are connected respectively to the first and second outputs of the software device, the third output of which is connected to the control input of the set threshold level of the comparison signal of the second comparator, the output of which is connected to the first input of the circuit OR, the second input of which is connected to the output of the second threshold element, the output of the circuit OR - with the second control input of the key, with the control input of the stepper drive tape drive mechanism, with the input of the threshold setting of the control unit for the threshold level of the comparator comparison signal and with the inputs of zeroing the software device, the first and second pulse counters, the second and third pulse integrators with adjustable integration time, the weight integrator and the first pulse integrator with adjustable integration time, the input of which connected to the first output of the first comparator, the third output of which is connected to the first control input of the key, the input registering ra managed connected to the output of the amplifier, the output of the first inverter - a second input of the first synchronous signal amplitudes adder whose output is connected also to the input of the third unit of the quadratic transformation of the signal amplitude, the first counter output is connected to a control input of the third amplifier and a third input device software.

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