CN114113293A

CN114113293A - Active sensitivity compensation method for photoionization detector, detector and detector

Info

Publication number: CN114113293A
Application number: CN202111261666.9A
Authority: CN
Inventors: 陈海永; 张华杰; 武传伟; 王栋; 侯贤祥; 李冬
Original assignee: Hanwei Electronics Group Corp
Current assignee: Hanwei Electronics Group Corp
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2022-03-01
Anticipated expiration: 2041-10-28
Also published as: CN114113293B

Abstract

The invention provides an active sensitivity compensation method for a photoionization detector, the detector and the detector, wherein the method comprises the following steps: monitoring the temperature and humidity of the photoionization reference gas chamber in real time, and judging whether the temperature and humidity conditions of gas detection are met; if yes, acquiring a current value IR of the response of the reference collecting electrode_p0(ii) a Judging the current value IR_p0Whether the current value is within a set current range or not, if so, acquiring a current value IM responded by the main circuit collecting electrode, and connecting the current value IM with the current value IR_p0The difference value delta I is used as the response current of the gas to be detected; otherwise, the active sensitivity compensation is carried out on the photoionization detector by dynamically adjusting the low-voltage maintaining voltage or the high-voltage lighting voltage of the photoionization detector, and whether the active sensitivity compensation is effective or not is judged. The invention dynamically adjusts the high-voltage lighting voltage and the low-voltage maintaining voltage, achieves the purpose of active sensitivity compensation, and reduces the influence of device aging and the like on the photoionization gas detection system.

Description

Active sensitivity compensation method for photoionization detector, detector and detector

Technical Field

The invention relates to the technical field of photoionization detectors, in particular to an active sensitivity compensation method of a photoionization detector, a detector and a detector.

Background

Photoionization detection technology is increasingly widely used as an accurate and effective detection means for VOCs. The basic principle of a PID (photo Ionization detector) photoionization detector is as follows: by utilizing the ultraviolet rays generated by the inert gas vacuum discharge phenomenon, when gas molecules with ionization potential less than or equal to the energy of the ultraviolet rays absorb one photon, ionization is generated to generate ions and electrons with positive electricity. In the ionization chamber, ions and electrons rapidly move towards a metal electrode under the action of an external electric field, a weak current signal is generated between the two electrodes, and the concentration of organic matters is detected after the current signal is amplified by a weak signal amplification circuit.

Although the photoionization detection technology has the characteristics of safety, real-time performance and the like, when the gas to be detected contains water vapor or the temperature of the external environment changes, the sensitivity of the photoionization detector is influenced; in addition, the PID lamp has a certain service life, and under the condition of keeping the voltage of the PID lamp to be certain, the sensitivity of the PID lamp is attenuated along with the lengthening of the running time of the photoionization detector, so that the sensitivity and the detection precision of the photoionization detector are influenced.

Aiming at the problem that the sensitivity of the photoionization detector gradually attenuates along with time, the method adopted in the market at present generally calibrates a concentration curve between response current of the photoionization detector and standard gas in a laboratory, and belongs to passive compensation. Because the sensitivity of the photoionization detector is a gradual attenuation process, a plurality of concentration calibration curves of the whole service life cycle of the photoionization detector need to be made, so that the sensitivity compensation can be well carried out, the concentration calibration curves take a long time, the labor cost is high, a large-memory processor is needed, and when the external environment and the environment during calibration are slightly changed, the sensitivity compensation cannot be accurately carried out by the pre-stored concentration curves.

In order to solve the above problems, people are always seeking an ideal technical solution.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides an active sensitivity compensation method for a photoionization detector, the detector and a detector.

In order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides a photoionization detector active sensitivity compensation method, which comprises the following steps:

monitoring the temperature and humidity of the photoionization reference gas chamber in real time, and judging whether the temperature and humidity conditions of gas detection are met;

if yes, acquiring a current value IR of the response of the reference collecting electrode_p0；

The current value IR_p0Comparing with a set current range to judge the current value IR_p0Whether the current is within a set current range;

if yes, acquiring a current value IM responded by the main circuit collecting electrode, and combining the current value IM with the current value IR_p0The difference value delta I is used as the response current of the gas to be detected;

otherwise, performing active sensitivity compensation on the photoionization detector by dynamically adjusting the low-voltage maintaining voltage or the high-voltage lighting voltage of the photoionization detector, and judging whether the active sensitivity compensation is effective or not;

if the active sensitivity compensation is effective, acquiring a current value IM responded by the main circuit collecting electrode, and comparing the current value IM with a current value IR 'responded by the reference collecting electrode after the active sensitivity compensation'_p0The difference value Δ I' is used as the response current of the gas to be measured.

A second aspect of the invention provides an active sensitivity compensation photoionization detector comprising a photoionization main circuit gas chamber, a photoionization reference gas chamber, a main circuit collection electrode pad, a reference collection electrode pad, a polarization electrode pad and a microcontroller, the main circuit collection electrode pad being located within the photoionization main circuit gas chamber, the reference collection electrode pad being located within the photoionization reference gas chamber;

the microcontroller is respectively connected with the main circuit collecting electrode slice, the reference collecting electrode slice and the polarized electrode slice so as to obtain the current value IR responded by the main circuit collecting electrode_p0And a current value IM of the reference collector electrode response;

the microcontroller also performs the steps of the method for active sensitivity compensation of a photoionization detector described above.

The invention provides an active sensitivity compensation photoionization detector, which comprises a main controller, an air filter, an air path on-off control component, a VOC (volatile organic compound) filter tank, an air path switching control component I, an air path connecting piece I, a photoionization detector, an air path connecting piece II and a sampling pump, wherein the photoionization detector comprises a photoionization main air chamber and a photoionization reference air chamber;

the air inlet of the air filter is used as a sample injection port;

an air outlet of the air filter is in sealed communication with an air inlet of the air path on-off control assembly, an air outlet of the air path on-off control assembly is in sealed communication with a first air inlet of the air path connecting piece I, and an air outlet of the air path connecting piece I is in sealed communication with an air inlet of the main photoionization air chamber, so that air containing gas to be detected is conveyed into the main photoionization air chamber of the photoionization detector;

the other air outlet of the air filter is in sealed communication with the air inlet of the VOC filtering tank; an air outlet of the VOC filter tank is in sealed communication with a first air inlet of an air circuit switching control assembly I, a first air outlet of the air circuit switching control assembly I is in sealed communication with a second air inlet of an air circuit connecting piece I, and a second air outlet of the air circuit switching control assembly I is in sealed communication with an air inlet of a photoionization reference air chamber, so that air which does not contain the gas to be detected is conveyed into the photoionization reference air chamber of the photoionization detector;

the gas outlet of the photoionization main gas chamber is in sealed communication with the first gas inlet of the gas circuit connecting piece II, the gas outlet of the photoionization reference gas chamber is in sealed communication with the second gas inlet of the gas circuit connecting piece II, the gas outlet of the gas circuit connecting piece II is in sealed communication with the gas inlet of the sampling pump, and the gas outlet of the sampling pump is used as a sample outlet;

and the main controller is respectively connected with the air path on-off control assembly, the air path switching control assembly I and the photoionization detector, and executes the steps of the active sensitivity compensation method of the photoionization detector.

The invention provides a method for compensating the active sensitivity of a photoionization detector, which comprises the following steps:

each photoionization detection cycle includes a calibration time period and a detection time period;

entering a calibration time period, and acquiring a current value I of a collector response in the calibration time period_p0Applying the current value I_p0Comparing with a set current range, and judging the current value I_p0Whether the current is within a set current range;

if yes, entering a detection time period, acquiring a current value IC receiving the electrode response in the detection time period, and connecting the current value IC with the current value I_p0The difference value delta I is used as the response current of the gas to be detected;

if the active sensitivity compensation is effective, entering a detection time period, acquiring a current value IC of collecting electrode response in the detection time period, and comparing the current value IC with a current value I 'of collecting electrode response after the active sensitivity compensation'_p0The difference value Δ I' is used as the response current of the gas to be measured.

A fifth aspect of the invention provides a computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by the processor, implements the steps of the method of photoionization detector active sensitivity compensation (dual gas cell) as described above.

A sixth aspect of the invention provides another computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by the processor, implements the steps of the method (single gas cell) of photoionization detector active sensitivity compensation as described above.

Compared with the prior art, the invention has prominent substantive characteristics and remarkable progress, particularly:

1) the invention provides an active sensitivity compensation method for a photoionization detector with double air chambers, which is different from a passive sensitivity compensation method, and dynamically adjusts high-voltage lighting voltage or low-voltage maintaining voltage according to the current value of a reference collecting electrode obtained in real time in the gas concentration detection process, so that the current value of the reference collecting electrode is between the set PID detection current upper limit and the PID detection current lower limit, the purpose of active sensitivity compensation is achieved, and the influence of factors such as device aging on the detection sensitivity of the photoionized gas is reduced;

2) the invention also provides a photoionization detector with a single lamp-three-electrode structure, which is provided with a photoionization main path air chamber and a photoionization reference air chamber, wherein the sample gas only passing through the air filter enters the photoionization main path air chamber, and the sample gas sequentially passing through the air filter and the VOC filter tank enters the photoionization reference air chamber;

when the concentration of the gas to be detected is detected, the main circuit collecting electrode plate in the main circuit gas chamber of the photoionization and the reference collecting electrode plate in the reference gas chamber of the photoionization both have current; the current value responded by the main path collecting electrode is differed from the current value responded by the reference collecting electrode, so that the influence of water vapor on the detection sensitivity of the photoionized gas is eliminated;

3) the invention provides an active sensitivity compensation method for a photoionization detector of a single air chamber, which comprises the steps of enabling air which does not contain gas to be detected to enter an ionization chamber in a calibration time period in a time-sharing multiplexing mode, and dynamically adjusting high-voltage lighting voltage or low-voltage maintaining voltage according to a current value of a collecting electrode obtained in real time in the calibration time period, so that the current value of collecting electrode response in the calibration time period is between a set PID detection current upper limit and a set PID detection current lower limit, and the purpose of active sensitivity compensation is achieved;

in addition, the current value of the response of the collecting electrode in the detection time period is different from the current value of the response of the collecting electrode in the calibration time period, so that the influence of water vapor on the detection sensitivity of the photoionized gas is eliminated;

4) the invention also carries out constant temperature treatment on the photoionization main circuit air chamber and the photoionization reference air chamber, and the temperature is generally higher than the external environment, so that the acquisition flow of the sampling pump is not fluctuated due to the temperature change; the detector is free from carrying out a calibration curve between concentration and temperature; the content that the gas that awaits measuring that further reduces to enter into the ionization chamber through the mode of heating contains steam, and then makes equipment can work under the harsher environment of humiture, shortens product development cycle, reduces human cost and material cost.

Drawings

FIG. 1 is a flow chart of the method for active sensitivity compensation of a photoionization detector in example 1;

FIG. 2 is a flow chart of the present invention for dynamically adjusting the low voltage holding voltage or the high voltage lighting voltage of the photoionization detector;

FIG. 3 is a flow chart of the method for compensating the active sensitivity of the photoionization detector (single air chamber time division multiplexing) in example 4;

FIG. 4 is a schematic diagram of the structure of an active sensitivity compensated photoionization detector (dual gas cell) of the present invention;

FIG. 5 is a schematic diagram of the construction of the photoionization detector (dual gas cell) of the present invention;

fig. 6(a) is a schematic structural view of a collecting electrode sheet of a photoionization detector (double gas cell);

fig. 6(b) is a schematic structural view of a polarized electrode sheet of the photoionization detector (double gas cell);

fig. 6(c) is a schematic view of the structure of the electrode substrate of the photoionization detector (double gas cell);

FIG. 7 is a schematic diagram of the structure of an active sensitivity compensated photoionization detector (single gas cell);

in the figure: 1. an air filter; 2. the air path on-off control component; 3, a VOC filtering tank; 4. the gas circuit switching control assembly I; 5. a gas circuit connecting piece I; 6. a photoionization detector; 61. photoionizing the main gas chamber; 62. photoionizing the reference gas cell; 63. collecting electrode slices in the main road; 64. a reference collecting electrode sheet; 65. polarizing the electrode plate; 66. an electrode base plate; a PID lamp; 68. a main path air chamber air inlet; 69. a reference air chamber air inlet; 7. a gas circuit connecting piece II; 8. a sampling pump; 9. a single-cell photoionization detector; 10. a gas circuit switching control component II; 11. a heating block; 12. a heat preservation box.

Detailed Description

The technical solution of the present invention is further described in detail by the following embodiments.

Example 1

Figure 1 shows a flow chart of a method of active sensitivity compensation for a photo-ionization detector comprising the steps of:

if the current value IR_p0Within a set current range, acquiring a current value IM responded by the main circuit collecting electrode, and combining the current value IM with the current value IR_p0The difference value delta I is used as the response current of the gas to be detected;

It will be appreciated that if reference is made to the current value IR of the collecting electrode response_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdIn between, it means that active sensitivity compensation is not required for the photoionization detector, and at the moment, the high-voltage lighting voltage V is ensured_I0And a low voltage holding voltage V_k0And is not changed.

In addition, if the current value of the reference collecting electrode response after the active sensitivity compensation is detected at the set PID upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective; otherwise, the active sensitivity compensation is judged to be invalid.

Specifically, PID detects the upper current limit I_puAnd PID detection lower current limit I_pdThe empirical values are set before shipment.

As shown in fig. 2, the active sensitivity compensation is performed on the photoionization detector by dynamically adjusting the low voltage holding voltage or the high voltage lighting voltage of the photoionization detector, and when it is determined that the active sensitivity compensation is valid, the following steps are performed:

setting the first step as S1, the second step as S2, and the third step as S3;

if reference is made to the current value IR of the collecting electrode response_p0Upper limit of PID detection current I > set_puAnd then:

gradually adjusting the current low-voltage maintaining voltage of the PID lamp by a set first step S1, and gradually reducing the current low-voltage maintaining voltage of the PID lamp; adjusted low voltage holding voltage = current low voltage holding voltage-number of steps N1 × first step S1;

if the regulated low-voltage maintaining voltage is greater than or equal to the lower limit value V of the low-voltage maintaining voltage_kdAnd the current value of the reference collector electrode response is acquired againIR’_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the current low-voltage maintaining voltage of the PID lamp is adjusted to be smaller than the lower limit value V of the low-voltage maintaining voltage_kdPost, current value IR 'of the acquired reference collector response'_p0Is also larger than the set PID detection current upper limit I_puIf so, judging that the active sensitivity compensation is invalid and prompting the equipment failure;

if the set PID base detects the current I_p< current value IR of reference collecting electrode response_p0< set PID detection Current lower Limit I_pdAnd then:

gradually adjusting the current low-voltage maintaining voltage of the PID lamp by a set second step S2, where the adjusted low-voltage maintaining voltage = the current low-voltage maintaining voltage + the number of steps N2 × the second step S2;

if the regulated low-voltage maintaining voltage is less than or equal to the set upper limit value V of the low-voltage maintaining voltage_kuAnd the current value IR 'of the reference collector response is again obtained'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the current low-voltage maintaining voltage of the PID lamp is adjusted to be larger than the set upper limit value V of the low-voltage maintaining voltage_kuPost, current value IR 'of the acquired reference collector response'_p0Is still less than the set PID detection current lower limit I_pdIf the active sensitivity compensation is invalid, prompting to clean the PID lamp;

if reference is made to the current value IR of the collecting electrode response_p0PID basic detection current I less than or equal to set value_pAnd then:

gradually adjusting the current high-voltage lighting voltage of the PID lamp by a set third step S3, wherein the adjusted high-voltage lighting voltage = the current high-voltage lighting voltage + the step number N3 × the third step S3;

if the adjusted high-voltage lighting voltage is less than or equal to the upper limit value V of the high-voltage lighting voltage_luAnd the current value IR 'of the reference collector response is again obtained'_p0Detecting current at set PIDUpper limit of I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the high-voltage lighting voltage of the PID lamp is adjusted to be larger than the set high-voltage lighting voltage upper limit value V_luPost, current value IR 'of the acquired reference collector response'_p0And less than or equal to the set PID basic detection current I_pAnd judging that the active sensitivity compensation is invalid and prompting that the PID lamp is broken.

It is understood that the equipment failure may be caused by other part failures besides the PID lamp, such as power supply abnormality, etc.; the damaged PID lamp refers to the failure of the photoionization detector caused by the long service time and the aging of the device.

It should be noted that, in the process of gradually adjusting the current low-voltage holding voltage of the PID lamp by the set first step S1, after each adjustment, it is determined whether the adjusted low-voltage holding voltage is greater than or equal to the lower limit V of the low-voltage holding voltage_kdIf yes, loading the adjusted PID lamp low-voltage maintaining voltage, and acquiring the current value IR 'of the reference collecting electrode response again'_p0,And judging current value IR'_p0If the current value is within the set current range, acquiring a current value IM responded by the main circuit collecting electrode if the current value is within the set current range, and comparing the current value IM with a current value IR 'responded by the reference collecting electrode after the active sensitivity compensation'_p0The difference value delta I' is used as the response current of the gas to be detected; if current value IR'_p0If the current is not within the set current range, performing the next adjustment with the set first step S1; up to a current value IR 'of the active sensitivity compensated reference collector electrode response'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdOr the low-voltage holding voltage is not at the lower limit value V of the low-voltage holding voltage_kdAnd a low voltage holding voltage upper limit value V_kuIn the meantime.

The process of adjusting the current low voltage sustain voltage of the PID lamp in a set second step S2 step by step, and the process of adjusting the current high voltage lighting voltage of the PID lamp in a set third step S3 step by step, will not be described in detail herein.

Specifically, in order to compromise the efficiency and accuracy of the active sensitivity compensation, the third step S3 is generally larger than the first step S1 and the second step S2; the first step S1 and the second step S2 may be equal or unequal, or may be adjusted in real time.

It can be understood that, in the process of dynamically adjusting the high-voltage lighting voltage, if the adjusted high-voltage lighting voltage is less than or equal to the upper limit value V of the high-voltage lighting voltage_luAnd loading the adjusted high-voltage lighting voltage, and acquiring the current value IR 'responded by the reference collecting electrode again after lighting operation is carried out again'_p0And judging current value IR'_p0Whether it is within the set current range.

The lighting voltage and the holding voltage of the PID lamp directly influence the current generated by ionizing the gas to be detected, namely the sensitivity and the detection precision of the PID detector are influenced; therefore, when the photoionization detector needs active sensitivity compensation, the PID detector keeps the zero constant by dynamically adjusting the lighting voltage and the holding voltage of the PID lamp in real time, and further ensures the sensitivity of the PID lamp.

It should be noted that the present invention refers to the current IR of the collecting electrode_p0The matching result with the set current range is the trigger condition if the current value IR_p0Matching with the set current range, active sensitivity compensation is not needed, and the current value IM of the main circuit collecting electrode response is subtracted by the current value IR_p0Obtaining the response current of the gas to be detected; if the current value IR_p0If the current is not matched with the set current range, active sensitivity compensation is carried out by adjusting high-voltage lighting voltage or low-voltage maintaining voltage, so that the method does not need to rely on a plurality of pre-calibrated concentration calibration curves; even if the external environment or the environment during calibration is slightly changed, active sensitivity compensation can be performed on site, in real time, dynamically and accurately, and the detection precision and the service life of the pump-suction type photoionization detector can be greatly improved.

Example 2

As shown in fig. 5 and fig. 6(a) to 6(c), this embodiment shows an embodiment of an active sensitivity compensation photoionization detector:

the photoionization detector comprises a PID lamp 67, a photoionization main gas chamber 61, a photoionization reference gas chamber 62, a main gas collecting electrode sheet 63, a reference collecting electrode sheet 64, a polarized electrode sheet 65 and a microcontroller, wherein the main gas collecting electrode sheet 63 is positioned in the photoionization main gas chamber 61, the reference collecting electrode sheet 64 is positioned in the photoionization reference gas chamber 62, one part of the polarized electrode sheet 65 is positioned in the photoionization main gas chamber 61, and the other part of the polarized electrode sheet 65 is positioned in the photoionization reference gas chamber 62;

the microcontroller is connected to the main circuit collecting electrode slice 63, the reference collecting electrode slice 64 and the polarization electrode slice 65 respectively to obtain the current value IR of the main circuit collecting electrode response_p0And a current value IM of the reference collector electrode response;

the microcontroller also performs the steps of the method for active sensitivity compensation of a photoionization detector of embodiment 1.

It can be understood that the photoionization detector of the single lamp-three electrode structure is provided with a main photoionization gas chamber 61 and a reference photoionization gas chamber 62, the two gas chambers can share one PID lamp 67, and ultraviolet rays emitted by the PID lamp 67 can irradiate into the main photoionization gas chamber 61 and the reference photoionization gas chamber 62; the two air chambers can also be respectively provided with a PID lamp, and the voltage adjustment of the PID lamps in the two air chambers is kept consistent at the moment.

It should be noted that a partition plate is arranged between the main photoionization gas chamber 61 and the reference photoionization gas chamber 62 of the photoionization detector 6, so that the gas between the main photoionization gas chamber 61 and the reference photoionization gas chamber 62 is not communicated; one side of the main photoionization gas chamber 61 is provided with a main gas chamber air inlet 68, and the other side is provided with a main gas chamber air outlet; one side of the photoionization reference gas chamber 62 is provided with a reference gas chamber inlet 69 and the other side is provided with a reference gas chamber outlet.

The sample gas only passing through the air filter 1 enters a main photoionization gas chamber 61, and the sample gas passing through the air filter 1 and the VOC filtering tank 3 in sequence enters a reference photoionization gas chamber 62; when the concentration of the gas to be detected is detected, the main circuit collecting electrode plate 63 in the photoionization main circuit gas chamber 61 and the reference collecting electrode plate 64 in the photoionization reference gas chamber 62 both have current; and (3) subtracting the current value responded by the main path collecting electrode from the current value responded by the reference collecting electrode, so that the influence of water vapor on the detection sensitivity of the photoionized gas is eliminated.

It can be understood that when the gas to be measured is contained in the region to be measured, the current value of the main collecting electrode response of the photoionization detector is more than the current value of the reference collecting electrode response; when the gas to be measured is not contained in the region to be measured or the concentration of the gas to be measured is extremely low, the current value of the main circuit collecting electrode response of the photoionization detector = the current value of the reference collecting electrode response.

Specifically, when the electrode plate is installed, the collecting electrode plate is arranged above the polarized electrode plate; the pins on the two sides of the main collecting electrode slice 63 are bent and then welded to the main collecting electrode connection position on the electrode base plate 66, and the pins on the two sides of the reference collecting electrode slice 64 are bent and then welded to the reference collecting electrode connection position on the electrode base plate 66; the polarized electrode plate 65 is shared, and four pins of the polarized electrode plate 65 are bent and then welded to the polarized electrode connection position on the electrode base plate 66; the improved active sensitivity compensation photoionization detector is in a single-lamp-three-electrode structure.

Further, the photoionization detector 6 is also provided with a heating block 11, and the heating block 11 is fixed outside the shell of the photoionization detector 6 through a heat preservation box 12, so that the main photoionization gas chamber and the reference photoionization gas chamber are constant in temperature (generally higher than the external environment); and a temperature and humidity sensor is further arranged in the photoionization reference gas chamber 62, and the temperature and humidity sensor and the heating block 11 are connected with the microcontroller so as to monitor the temperature and humidity conditions in the ionization chamber in real time. The microcontroller judges whether the photoionization reference gas chamber 62 meets the set gas detection condition or not through the temperature and humidity sensor, and when the set gas detection condition is not met, the water vapor content in the gas to be detected entering the ionization chamber is further reduced through a heating mode, so that the equipment can work in a more severe temperature and humidity environment, the product development period is shortened, and the labor cost and the material cost are reduced; therefore, the detector avoids the calibration curve between concentration and temperature, and can further eliminate the influence of water vapor on the sensitivity and detection precision of the photoionization detector.

Example 3

As shown in fig. 4, the present embodiment provides an active sensitivity compensation photoionization detector, which includes a main controller, an air filter 1, an air channel on-off control component 2, a VOC filter tank 3, an air channel switching control component i 4, an air channel connector i 5, a photoionization detector 6, an air channel connector ii 7, and a sampling pump 8, where the photoionization detector 6 includes a main photoionization air chamber 61 and a reference photoionization air chamber 62;

the air inlet of the air filter 1 is used as a sample injection port;

an air outlet of the air filter 1 is in sealed communication with an air inlet of the air path on-off control assembly 2, an air outlet of the air path on-off control assembly 2 is in sealed communication with a first air inlet of the air path connector I5, and an air outlet of the air path connector I5 is in sealed communication with an air inlet of the main photoionization air chamber 61, so that air containing gas to be detected is conveyed into the main photoionization air chamber 61 of the photoionization detector 6;

the other air outlet of the air filter 1 is in sealed communication with the air inlet of the VOC filtering tank 3; the air outlet of the VOC filter tank 3 is in sealed communication with a first air inlet of the air circuit switching control component I4, the first air outlet of the air circuit switching control component I4 is in sealed communication with a second air inlet of the air circuit connecting piece I5, and the second air outlet of the air circuit switching control component I4 is in sealed communication with an air inlet of the photoionization reference air chamber 62, so that air which does not contain the gas to be detected is conveyed into the photoionization reference air chamber 62 of the photoionization detector 6;

the air outlet of the photoionization main path air chamber 61 is in sealed communication with the first air inlet of the air path connecting piece II 7, the air outlet of the photoionization reference air chamber 62 is in sealed communication with the second air inlet of the air path connecting piece II 7, the air outlet of the air path connecting piece II 7 is in sealed communication with the air inlet of the sampling pump 8, and the air outlet of the sampling pump 8 is used as a sample outlet;

the main controller is respectively connected with the air path on-off control assembly 2, the air path switching control assembly I4 and the photoionization detector 6, and executes the steps of the active sensitivity compensation method of the photoionization detector in the embodiment 1.

The air filter 1 mainly achieves the function of preprocessing sample gas, namely filtering particle dust, macromolecular water drops and partial water vapor in ambient air and gas to be detected so as to prevent small particles or water vapor from entering an air chamber of a photoionization detector and influencing the detection precision and sensitivity of the photoionization detection system; the VOC filtering tank 3 filters volatile organic compounds in the gas or ambient air to be detected entering the air chamber, so that clean air is obtained and is used for cleaning the air chamber of the photoionization detector. The gas circuit on-off control assembly 2, the gas circuit switching control assembly I4, the gas circuit connecting piece I5, the gas circuit connecting piece II 7 and the sampling pump 8 are used for realizing dynamic switching of gas circuit detection and cleaning functions.

It is understood that the main controller changes the output voltage of the boost circuit by controlling the DAC, and further changes the lighting voltage and the sustain voltage.

Specifically, the gas circuit on-off control component 2 is an electromagnetic two-way valve, the gas circuit switching control component I4 is an electromagnetic three-way valve, and the gas circuit connecting piece I5 and the gas circuit connecting piece II 7 are three-way quick connectors.

As shown in fig. 5 and fig. 6(a) to 6(c), the photoionization detector 6 further includes an electrode base plate 66, and a main path collecting electrode plate 63, a reference collecting electrode plate 64 and a polarized electrode plate 65 which are located on the electrode base plate 66, the main path collecting electrode plate 63 being located in the photoionization main path gas chamber 61, the reference collecting electrode plate 64 being located in the photoionization reference gas chamber 62; a portion of the polarized electrode plate 65 is located within the photoionization main gas chamber 61 and another portion of the polarized electrode plate 65 is located within the photoionization reference gas chamber 62.

Specifically, the sampling pump 8 is also externally provided with a heating block, so that the sampling pump keeps a constant temperature, the constant temperature is generally set to 45 degrees, and the pumping flow of the sampling pump is ensured not to change along with the change of the external environment temperature.

It should be noted that, as the operation time of the device increases, when the current value of the reference collecting electrode deviates from the set interval range, and the high-voltage lighting voltage and the low-voltage maintaining voltage both change to reach the upper limit value or the lower limit value, the current value of the reference collecting electrode still cannot be made to be within the specified range, and then the user or the manufacturer is prompted on the display interface that the PID lamp needs to be replaced to perform normal gas detection.

Further, the main controller firstly obtains the current value IR of the response of the reference collecting electrode_p0When, carry out:

step 101, electrifying and starting up, setting the temperature and humidity working range of the photoionization detector 6, and entering the preheating state of a gas circuit, a sampling pump and an ionization chamber to enable the temperature to be quickly constant to the set temperature;

step 102, monitoring the temperature and humidity in the photoionization reference gas chamber 62 in real time through a temperature and humidity sensor, and judging whether the temperature and humidity conditions of gas detection are met;

step 103, setting the upper limit value V of the high-voltage lighting voltage_luLower limit value V of high-voltage lighting voltage_ld、Upper limit value V of low-voltage maintaining voltage_kuAnd a lower limit value V of the low-voltage holding voltage_kd；

Performing PID lamp lighting operation according to the set high-voltage lighting voltage under the condition of satisfying the temperature and humidity of gas detection, and then adjusting the supply voltage of the PID lamp from the high-voltage lighting voltage to the set low-voltage maintaining voltage V_k0；

Step 104, closing the air path on-off control assembly 2 and the air path switching control assembly I4, and opening the sampling pump 8 to enable air which does not contain the gas to be detected to enter the photoionization reference air chamber 62, so as to clean the photoionization reference air chamber 62;

105, after the photoionization reference gas chamber 62 is cleaned for the preset time T1, the main controller reads the current value IR of the reference collecting electrode response through the analog-to-digital conversion module_p0。

In addition to active sensitivity compensation of the photoionization detector at power-up, the current value IR at the reference collecting electrode is measured throughout the gas detection process_p0Is not at the set PID detection current upper limit I_puAnd PID detection lower current limit I_pdIn any case, active sensitivity compensation is performed.

Specifically, the gas detection process is as follows:

step 201, closing the air path on-off control component 2, opening the air path switching control component I4, opening the sampling pump 8, and entering a cleaning state of the main photoionization air chamber 61;

step 202, after the main photoionization gas chamber 61 is cleaned for a preset time A, continuing to close the gas path on-off control component 2 and turn on the sampling pump 8, closing the gas path switching control component I4, and entering a cleaning state of the reference photoionization gas chamber 62;

step 203, after the photoionization reference gas chamber 62 is cleaned for the preset time B, continuing to close the gas path switching control assembly i 4 and open the sampling pump 8, opening the gas path on-off control assembly 2, and entering a photoionization gas detection state:

the gas to be detected enters a photoionization main path air chamber 61 through a sample injection port, an air filter 1, a gas path on-off control component 2 and a gas path connecting piece I5, and also enters a photoionization reference air chamber 62 through the sample injection port, the air filter 1, a VOC (volatile organic compound) filter tank 3, a gas path switching control component I4 and the gas path connecting piece I5;

the main controller reads the current value IR of the reference collecting electrode response through the analog-to-digital conversion module_p0Judging the current value IR_p0Whether the current is within a set current range;

if the current value IR_p0Within a set current range, reading a current value IM responded by the main circuit collecting electrode through an analog-to-digital conversion module, and combining the current value IM with the current value IR_p0The difference value delta I is used as the response current of the gas to be detected;

if the current value IR_p0If the current is not in the set current range, the low voltage maintaining voltage or the high voltage lighting voltage of the photoionization detector is dynamically adjusted to charge the photoionization detectorPerforming active sensitivity compensation; if the active sensitivity compensation is effective, acquiring a current value IM responded by the main circuit collecting electrode, and comparing the current value IM with a current value IR 'responded by the reference collecting electrode after the active sensitivity compensation'_p0The difference value delta I' is used as the response current of the gas to be detected;

step 204, closing the air path on-off control component 2, opening the air path switching control component I4, keeping the sampling pump 8 in an open state, and entering a cleaning state of the main photoionization air chamber 61;

step 205, closing the gas path switching control assembly I, opening the sampling pump, opening the gas path on-off control assembly 2, and entering a photoionization gas detection state;

thereafter, cycling between the main plenum cleaning state and the detection state occurs.

Example 4

This example presents a specific implementation of a method for compensating for the active sensitivity of a photoionization detector for a single cell photoionization detector;

as shown in fig. 3, the method for compensating the active sensitivity of the photoionization detector of the single gas chamber comprises the following steps:

if the active sensitivity compensation is effective, entering a detection time period and acquiring collection in the detection time periodThe current value IC of the electrode response is compared with the current value I 'of the collection electrode response after the active sensitivity compensation'_p0The difference value Δ I' is used as the response current of the gas to be measured.

Note that the calibration time period of the photoionization detection cycle is not fixed, and the current value I of the collector response is collected during the calibration time period_p0When the current is within the set current range, the calibration time period timing is ended, the detection time period timing is started, and the single-air-chamber photoionization detector 9 enters a detection state; when the detection time period reaches a preset time length, the detection state of the single-gas-cell photoionization detector 9 is ended, and the single-gas-cell photoionization detector 9 enters a calibration state.

In the detection process of the gas to be detected, the calibration time period and the detection time period are alternately and circularly carried out, and if the active sensitivity compensation is invalid in the calibration time period, the device is prompted to be in fault or the PID lamp is damaged, and the gas concentration detection cannot be carried out.

setting the first step as S1, the second step as S2, and the third step as S3;

if the current value I of the collector response in the calibration time period is received_p0Upper limit of PID detection current I > set_puAnd then:

gradually adjusting the current low-voltage maintaining voltage of the PID lamp by a set first step S1, the adjusted low-voltage maintaining voltage = the current low-voltage maintaining voltage-step N1 × first step S1;

if the regulated low-voltage maintaining voltage is greater than or equal to the lower limit value V of the low-voltage maintaining voltage_kdAnd the current value I of the collector response is collected in the calibration time period acquired again_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the current low-voltage maintaining voltage of the PID lamp is adjusted toLower than the lower limit value V of the low-voltage holding voltage_kdThen, the current value I 'of the collector response is acquired in the calibration time period'_p0Is also larger than the set PID detection current upper limit I_puIf so, judging that the active sensitivity compensation is invalid and prompting the equipment failure;

if the set PID base detects the current I_p< collecting the current value I of the collector response during the calibration period_p0< set PID detection Current lower Limit I_pdAnd then:

if the regulated low-voltage maintaining voltage is less than or equal to the set upper limit value V of the low-voltage maintaining voltage_kuAnd the current value I 'of the collector response is collected within the calibration period acquired again'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the current low-voltage maintaining voltage of the PID lamp is adjusted to be larger than the set upper limit value V of the low-voltage maintaining voltage_kuThen, the current value I 'of the collector response is acquired in the calibration time period'_p0Is still less than the set PID detection current lower limit I_pdIf the active sensitivity compensation is invalid, prompting to clean the PID lamp;

if the current value I of the collector response in the calibration time period is received_p0PID basic detection current I less than or equal to set value_pAnd then:

if the adjusted high-voltage lighting voltage is less than or equal to the upper limit value V of the high-voltage lighting voltage_luAnd the current value I 'of the collector response is collected within the calibration period acquired again'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the high voltage of the PID lamp is lightedThe voltage is adjusted to be larger than the set upper limit value V of the high-voltage lighting lamp_luThen, the current value I 'of the collector response is acquired in the calibration time period'_p0And less than or equal to the set PID basic detection current I_pAnd judging that the active sensitivity compensation is invalid and prompting that the PID lamp is broken.

It can be understood that, in the process of dynamically adjusting the high-voltage lighting voltage, if the adjusted high-voltage lighting voltage is less than or equal to the upper limit value V of the high-voltage lighting voltage_luAnd loading the adjusted high-voltage lighting voltage, and acquiring the current value I 'of the collector response in the calibration time period again after lighting operation is carried out again'_p0And judging the current value I'_p0Whether it is within the set current range.

Specifically, a schematic structural diagram of the active sensitivity compensation photoionization detector (single air chamber) is shown in fig. 7, and the detector comprises an air filter 1, a VOC filter tank 3, a single air chamber photoionization detector 9, an air path switching control component ii 10, a sampling pump 8 and a microcontroller; the microcontroller is respectively connected with the single-air-chamber photoionization detector 9, the air path switching control assembly II 10 and the sampling pump 8. In the calibration time period, the gas to be detected enters a single-air-chamber photoionization detector 9 through an air filter 1, a gas circuit switching control component II 10 and a VOC (volatile organic compound) filter tank 3; in the detection time period, the gas to be detected enters the single-air-chamber photoionization detector 9 through the air filter 1 and the air path switching control assembly II 10. Air which does not contain gas to be detected enters an ionization chamber of the single-air-chamber photoionization detector 9 in a calibration time period in a time-sharing multiplexing mode, and high-voltage lighting voltage or low-voltage maintaining voltage is dynamically adjusted according to the current value of the collecting electrode obtained in real time in the calibration time period, so that the current value of collecting electrode response in the calibration time period is between the set PID detection current upper limit and the PID detection current lower limit, the zero value is kept constant, and the purpose of active sensitivity compensation is achieved.

Specifically, the air path switching control assembly II 10 is an electromagnetic four-way valve.

Further, the single-air-chamber photoionization detector 9 is also provided with a heating block, and the heating block is fixed outside the shell through a heat preservation box; and a temperature and humidity sensor is further arranged in an ionization chamber of the single-air-chamber photoionization detector 9, and the temperature and humidity sensor and the heating block are connected with the microcontroller so as to monitor the temperature and humidity conditions in the ionization chamber in real time and judge whether set gas detection conditions are met. When the set gas detection condition is not met, the water vapor content in the gas to be detected entering the ionization chamber is further reduced in a heating mode, so that the equipment can work in a more severe environment with temperature and humidity, the product development period is shortened, and the labor cost and the material cost are reduced; therefore, the ionization chamber of the single-gas-chamber photoionization detector 9 is kept at a constant temperature (generally higher than the external environment) in the detection process, so that the detector is free from a calibration curve between concentration and temperature, and the influence of water vapor on the detection sensitivity and detection precision of the photoionization detector can be further eliminated.

Example 5

This embodiment presents a computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by the processor, implements the steps of the method of photoionization detector active sensitivity compensation as in embodiment 1.

This embodiment presents a further computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by the processor, implements the steps of the method of photoionization detector active sensitivity compensation as in embodiment 4.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.

Those of ordinary skill in the art will appreciate that the various illustrative algorithmic steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or as a combination of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

The above method, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow in the method of the embodiments described above may be implemented by a computer program, which may be stored in a computer-readable storage medium and can implement the steps of the embodiments of the methods described above when the computer program is executed by a processor. The computer program includes computer program code, and the computer program code may be in a source code form, an object code form, an executable file or some intermediate form.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.

Claims

1. An active sensitivity compensation method for a photoionization detector is characterized by comprising the following steps of:

2. The method for active sensitivity compensation of a photoionization detector of claim 1, wherein the active sensitivity compensation is performed on the photoionization detector by dynamically adjusting a low voltage holding voltage or a high voltage lighting voltage of the photoionization detector, and when the active sensitivity compensation is determined to be effective, the following steps are performed:

setting the first step as S1, the second step as S2, and the third step as S3;

if the regulated low-voltage maintaining voltage is greater than or equal to the lower limit value V of the low-voltage maintaining voltage_kdAnd the current value IR 'of the reference collector response is again obtained'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdJudging that the active sensitivity compensation is effective;

if the adjusted high-voltage lighting voltage is less than or equal to the upper limit value V of the high-voltage lighting voltage_luAnd the current value IR 'of the reference collector response is again obtained'_p0At a set PID detection current upper limit I_puAnd PID detection lower current limit I_pdIn between, then judgeThe constant active sensitivity compensation is effective;

3. An active sensitivity compensated photoionization detector, comprising: the main circuit collection electrode plate is positioned in the photoionization main circuit air chamber, and the reference collection electrode plate is positioned in the photoionization reference air chamber;

the microcontroller also performs the steps of the method for active sensitivity compensation of a photoionization detector of claim 1 or 2.

4. An active sensitivity compensated photoionization detector, comprising: the system comprises a main controller, an air filter, an air path on-off control assembly, a VOC (volatile organic compound) filter tank, an air path switching control assembly I, an air path connecting piece I, a photoionization detector, an air path connecting piece II and a sampling pump, wherein the photoionization detector comprises a main photoionization air chamber and a photoionization reference air chamber;

the air inlet of the air filter is used as a sample injection port;

the main controller is respectively connected with the air path on-off control assembly, the air path switching control assembly I and the photoionization detector and executes the steps of the active sensitivity compensation method of the photoionization detector in claim 1 or 2.

5. The active sensitivity compensated photoionization detector of claim 4 wherein the master controller initially obtains a current value IR to which the reference collection electrode is responsive_p0When, carry out:

step 101, electrifying and starting up, setting the temperature and humidity working range of the photoionization detector, and entering the preheating state of the ionization chamber to enable the photoionization detector to be quickly and constantly at the set temperature;

step 102, monitoring the temperature and humidity in a photoionization reference gas chamber in real time through a temperature and humidity sensor, and judging whether the temperature and humidity conditions of gas detection are met;

step 103, setting the upper limit value V of the high-voltage lighting voltage_luAt a low voltage holding voltageLimit value V_kuAnd a lower limit value V of the low-voltage holding voltage_kd；

Step 104, closing the air path on-off control assembly and the air path switching control assembly I, and opening the sampling pump to enable air which does not contain the gas to be detected to enter the photoionization reference air chamber to clean the photoionization reference air chamber;

105, after the photoionization reference gas chamber is cleaned for a preset time T1, the main controller reads the current value IR responded by the reference collecting electrode through the analog-to-digital conversion module_p0。

6. The active sensitivity compensated photoionization detector of claim 4, wherein: the photoionization detector further comprises a main circuit collecting electrode plate, a reference collecting electrode plate and a polarized electrode plate, wherein the main circuit collecting electrode plate is located in the photoionization main circuit air chamber, and the reference collecting electrode plate is located in the photoionization reference air chamber.

7. An active sensitivity compensation method for a photoionization detector is characterized by comprising the following steps of:

8. The method for active sensitivity compensation of a photoionization detector of claim 7, wherein the active sensitivity compensation is performed on the photoionization detector by dynamically adjusting a low voltage holding voltage or a high voltage lighting voltage of the photoionization detector, and when the active sensitivity compensation is determined to be effective, the following steps are performed:

setting the first step as S1, the second step as S2, and the third step as S3;

if the current low-voltage maintaining voltage of the PID lamp is adjusted to be smaller than the lower limit value V of the low-voltage maintaining voltage_kdThen, the current value I 'of the collector response is acquired in the calibration time period'_p0Is also larger than the set PID detection current upper limit I_puIf so, judging that the active sensitivity compensation is invalid and prompting the equipment failure;

if the set PID base detects the current I_pAt time of calibrationCurrent value I of collector response in time interval_p0< set PID detection Current lower Limit I_pdAnd then:

if the high-voltage lighting voltage of the PID lamp is adjusted to be larger than the set high-voltage lighting voltage upper limit value V_luThen, the current value I 'of the collector response is acquired in the calibration time period'_p0And less than or equal to the set PID basic detection current I_pAnd judging that the active sensitivity compensation is invalid and prompting that the PID lamp is broken.

9. A computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by a processor, performs the steps of a method of photoionization detector active sensitivity compensation according to claim 1 or 2.

10. A computer readable storage medium having stored thereon a photoionization detector active sensitivity compensation program that, when executed by a processor, performs the steps of a method of photoionization detector active sensitivity compensation according to claim 7 or 8.