CN109164118B - Calibration system and method of beta absorption type dust meter - Google Patents
Calibration system and method of beta absorption type dust meter Download PDFInfo
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- CN109164118B CN109164118B CN201810895135.7A CN201810895135A CN109164118B CN 109164118 B CN109164118 B CN 109164118B CN 201810895135 A CN201810895135 A CN 201810895135A CN 109164118 B CN109164118 B CN 109164118B
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- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
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Abstract
The invention relates to a calibration system and a calibration method of a beta absorption type dust meter. The calibration system comprises a standard membrane support for loading a standard membrane, a working filter belt, a counting module, a storage module and a calculating module, wherein the counting module is used for counting the pulse frequency of a beta radioactive source of the beta absorption dust meter passing through a blank working filter belt or the working filter belt tightly attached to the standard membrane, and the total counting amount is respectively recorded as N1 and N2; the storage module is used for storing the mass Δ m of the standard membrane and the N1 and N2 obtained by the counting module; the calculation module is used for calculating a k value by using the data stored by the storage module according to a formula of 1/k ln (N1/N2); and when the working filter belts tightly attached to the standard membranes are counted, the standard membranes of the standard membrane support are tightly attached to the upper parts of the working filter belts, and the distance between each standard membrane and each working filter belt is less than or equal to 0.3 mm. The calibration system and the calibration method thereof reduce errors caused by changes of detected geometric conditions.
Description
Technical Field
The invention relates to the field of weighing instruments, in particular to a calibration system and a calibration method of a beta absorption type dust measuring instrument.
Background
The beta radiation emitted by the radiation source can be converted into electrical pulses (frequency) using a radiation sensor and associated electronics. The beta absorption type dust measuring instrument utilizes the principle that when low-energy (<1MeV) beta rays pass through a substance, the energy of the beta rays is absorbed by the substance to generate attenuation, and the degree of the attenuation is related to the mass of the passing substance, namely: the change in pulse frequency is related to the mass of the penetrating substance.
The beta ray attenuation relationship is described by:
I＝I0e-kΔmt。
wherein, I0: radiation intensity of β source, I: intensity of beta radiation after passing through a substance, k: mass absorption coefficient (cm)2,/mg), Δ mt: total mass per unit area (mg/cm) of material passed through2)。
In order to eliminate errors caused by the fluctuation phenomenon of the radioactive source, the beta absorption type dust meter needs to count and count the pulse frequency (generally 2 minutes) when in work.
Under certain conditions, the counting frequency N is proportional to the radiation intensity I, i.e.:
N∝I∝I0e-kΔmt。
the sampling method of the beta absorption dust meter is a filter belt filtration type. And if the unit area mass of the blank filter belt which is not sampled is delta mt, the increment of the sampled unit area mass is delta m, the statistical counting time is Ts, the counting value on the blank filter belt is N1, and the counting value after sampling is N2, then:
N1＝Ts I0e-kΔmt
N2＝Ts I0e-k(Δmt+Δm)
it can be solved that: Δ m is 1/k ln (N1/N2).
Thereby obtaining the mass increment Δ m per unit area after sampling.
Before the beta absorption type dust meter is used, the instrument is calibrated by using a standard diaphragm with known mass (delta m), and the correction coefficient k value (namely the mass absorption coefficient) of the instrument is obtained according to the beta ray attenuation relational expression. The beta absorption type dust meter needs to be repeatedly inserted by the standard diaphragm (manual action or special mechanical transmission action) during the primary calibration, count statistics of N1 and N2 is carried out, the k value of the instrument is calculated, and the k value is kept in the instrument and is used as an instrument constant to participate in the output operation of the instrument. Because the beta absorption type dust meter is a metering instrument, calibration work needs to be carried out at regular time so as to ensure the stability and accuracy of the k value.
But the relevant standard (HJ 653-2013) does not specify an explicit method of operation for scaling. Due to different operation methods, the phenomenon that the same quality standard membrane outputs different data on different instruments occurs. However, if the standard diaphragm is not used properly, the correction factor of the instrument will be in error from the normal use of the instrument. This error has a large impact on instruments with output values on the order of micrograms (μ g).
Disclosure of Invention
The invention aims to provide a calibration system and a calibration method of a beta absorption type dust meter aiming at the condition of disordered calibration operation of the beta absorption type dust meter, and a large amount of practices prove that the calibration system and the calibration method are most in line with the working principle of the beta absorption type dust meter.
The invention provides a calibration system of a beta absorption type dust meter, wherein the calibration system comprises a standard membrane support loaded with a standard membrane, a working filter belt, a counting module, a storage module and a calculation module, wherein the counting module is used for counting the pulse frequency of a beta radioactive source of the beta absorption type dust meter passing through a blank working filter belt or a working filter belt tightly attached to the standard membrane, and the total counting amount is respectively marked as N1 and N2; the storage module is used for storing the mass Δ m of the standard membrane and the N1 and N2 obtained by the counting module; the calculation module is used for calculating a k value by using the data stored by the storage module according to a formula of 1/k ln (N1/N2); and when the working filter belts tightly attached to the standard membranes are counted, the standard membranes of the standard membrane support are tightly attached to the upper parts of the working filter belts, and the distance between each standard membrane and each working filter belt is less than or equal to 0.3 mm.
Preferably, according to the aforementioned calibration system, wherein the mass of said standard membrane is not greater than 1.2mg/cm2。
Or preferably, according to the aforementioned calibration system, wherein said standard membrane holders are three standard membrane holders that transfer standard membranes of different qualities. Preferably 0.3mg/cm2、0.6mg/cm2And 0.9mg/cm2。
More preferably, the calibration system according to the foregoing, wherein the calculating module is further configured to calculate an average number of N1 and N2 using the data stored in the storage module, and further calculate a k value by using the average numbers of the formulas Δ m ═ 1/k ln (N1/N2), N1 and N2.
Still preferably, the calibration system according to the foregoing, wherein the calculating module is further configured to calculate an average value of k values of adjacent quality standard diaphragms as the piecewise correction coefficient.
The invention also provides a method for using the calibration system, wherein the method comprises the following steps:
(1) the storage module stores the standard diaphragm mass delta m of the standard diaphragm support;
(2) counting the pulse frequency of a beta radioactive source of the beta absorption type dust measuring instrument passing through the blank working filter belt by adopting the counting module, wherein the total counting amount is N1, and N1 is stored in the storage module;
(3) tightly attaching the standard membrane of the standard membrane support above the counting position of the blank working filter belt, wherein the distance between the standard membrane and the counting position of the blank working filter belt is less than or equal to 0.3 mm;
(4) counting the pulse frequency of a beta radioactive source of the beta absorption type dust measuring instrument passing through the working filter belt tightly attached to the standard membrane by adopting the counting module, wherein the total counting amount is N2, and N2 is stored in the storage module;
(5) and calculating a k value by using the calculation module according to the formula of 1/k ln (N1/N2).
Preferably, the method according to the preceding, wherein the counting time of steps (2) and (4) is 6 minutes.
More preferably, the method according to the preceding, wherein the method comprises:
the mass of the standard membrane is 0.3mg/cm2Repeating the steps (1) to (5) to obtain a k1 value;
the mass of the standard membrane is 0.6mg/cm2Repeating the steps (1) to (5) to obtain a k2 value;
the mass of the standard membrane is 0.9mg/cm2Repeating the steps (1) to (5) to obtain a k3 value;
calculating the average value k of k1 and k2 by using the calculation module12And the average value k of k2 and k323；
k1 is less than 0.3mg/cm2Fractional correction factor of, k12Is 0.3-0.6mg/cm2Fractional correction factor of, k23Is 0.6-0.9mg/cm2The coefficient of segmental correction of (k 3) is > 0.9mg/cm2The piecewise correction coefficient of (1).
Or more preferably, the method according to the foregoing, wherein step (5) of the method further comprises: repeating the steps (2) to (4) to obtain a plurality of total counting amounts N1 and N2, storing the total counting amounts into the storage module, wherein the number of times of repetition is not less than 10, and the calculating module calculates the average number of the total counting amounts N1 and N2 respectively;
step (5) is that the calculation module calculates the k value by the average of the formulas Δ m ═ 1/k ln (N1/N2), N1, and N2.
Still preferably, the method according to the preceding, wherein the method comprises:
the mass of the standard membrane is 0.3mg/cm2Repeating the steps (1) to (5) to obtain a k1 value;
the above-mentionedThe standard membrane has a mass of 0.6mg/cm2Repeating the steps (1) to (5) to obtain a k2 value;
the mass of the standard membrane is 0.9mg/cm2Repeating the steps (1) to (5) to obtain a k3 value;
calculating the average value k of k1 and k2 by using the calculation module12And the average value k of k2 and k323；
k1 is less than 0.3mg/cm2Fractional correction factor of, k12Is 0.3-0.6mg/cm2Fractional correction factor of, k23Is 0.6-0.9mg/cm2The coefficient of segmental correction of (k 3) is > 0.9mg/cm2The piecewise correction coefficient of (1).
Various beta absorption type dust meters are measuring instruments equivalent to a weighing method (a classical method) in principle. It is based on the absorption and attenuation rule of ray in matter to weigh and measure the sample collected from atmosphere. There is a strict adherence to the calibration of such instruments: any change in the geometry during the test affects the result of the test, i.e. the measurement position of the calibration membrane must be the same as the actual sample position.
The calibration system and the calibration method thereof provided by the invention enable the standard membrane to be positioned above the working filter belt and tightly attached to the working filter belt, and fix the working filter belt, thereby reducing errors caused by change of detected geometric conditions. By adopting the calibration system and the calibration method thereof, the output data of the similar instruments of various manufacturers is comparable, and the reliability of the output data of the instruments is improved.
Detailed Description
The following detailed description of the embodiments of the present invention will be given in conjunction with examples to better understand the aspects of the present invention and the advantages of its various aspects. However, the specific embodiments and examples described below are for illustrative purposes only and are not limiting of the invention.
The invention provides a calibration system of a beta absorption type dust meter, which comprises a standard membrane support for loading a standard membrane, a working filter belt, a counting module, a storage module and a calculation module. The counting module is used for counting the pulse frequency of a beta radioactive source of the beta absorption type dust meter passing through the blank working filter belt or the working filter belt tightly attached to a standard membrane, and the total counting amount is respectively marked as N1 and N2; the storage module is used for storing the mass Δ m of the standard membrane and the N1 and N2 obtained by the counting module; the calculation module is used for calculating a k value by using the data stored by the storage module according to a formula of 1/k ln (N1/N2).
When the system is used for calibration, the following calibration method can be adopted:
(1) the storage module stores the standard diaphragm mass Δ m of the standard diaphragm support. The concentration range of the beta absorption type dust meter for long-term monitoring is 0.3mg/m3Therefore, the mass Δ m of the standard membrane is preferably not more than 1.2mg/cm2。
(2) And counting the pulse frequency of the beta radioactive source of the beta absorption type dust measuring instrument passing through the blank working filter belt by adopting the counting module, wherein the total counting amount is N1, and N1 is stored in the storage module. The counting time is preferably 6 minutes.
(3) And tightly attaching the standard membrane of the standard membrane support above the counting position of the blank working filter belt, wherein the distance between the standard membrane and the counting position of the blank working filter belt is less than or equal to 0.3 mm. The standard membrane must be located above the working filter belt, which is the closest state to the sample being taken. The standard membrane is placed against the working filter to reduce errors due to changes in the detected geometry. And because the working filter belt has non-uniformity and can influence calibration, the position of the working filter belt needs to be fixed, so that the standard membrane is positioned above the counting position of the blank working filter belt.
(4) And counting the pulse frequency of the beta radioactive source of the beta absorption type dust meter passing through the working filter belt tightly attached to the standard membrane by adopting the counting module, wherein the total counting amount is N2, and N2 is stored in the storage module. The counting time is preferably 6 minutes.
(5) And calculating a k value by using the calculation module according to the formula of 1/k ln (N1/N2).
Preferably, before step (5), the calibration method further comprises: repeating the steps (2) to (4) to obtain a plurality of total counting amounts N1 and N2, storing the total counting amounts into the storage module, repeating the times not less than 10 times, and respectively calculating the average number of the total counting amounts N1 and N2 by the calculation module. Step (5) is that the calculation module calculates the k value by the average of the formulas Δ m ═ 1/k ln (N1/N2), N1, and N2. And repeating the counting for multiple times to eliminate radioactive fluctuation errors.
In one embodiment, in the calibration system, the standard membrane holders are three standard membrane holders that transfer standard membranes of different qualities. Preferably, the mass of the standard membrane is 0.3mg/cm respectively2、0.6mg/cm2And 0.9mg/cm2. And (3) performing linear calibration on the beta absorption type dust meter by adopting the three standard membranes.
When the system is used for calibration, the following calibration method can be adopted:
(1) 3 measured standard films were prepared and the respective masses were designated Δ m1(0.3 mg/cm)2)、Δm2(0.6mg/cm2) And Δ m3(0.9 mg/cm)2) Stored in the storage module.
(2) The working filter belt is fixed well and does not move when being calibrated.
(3) And counting the pulse frequency of the beta radioactive source of the beta absorption type dust measuring instrument passing through the blank working filter belt by adopting the counting module, wherein the counting time is 6 minutes, the counting total amount is N1, and storing the counting time into the storage module.
(5) The unit mass is 0.3mg/cm2The standard membrane is tightly attached to the same position of the working filter belt.
(6) Counting the working filter belt tightly attached to the standard membrane for 6 minutes, wherein the total counting amount is N2, and storing the working filter belt into the storage module;
(7) repeating the steps (3) to (6) to obtain a plurality of N1 and N2, wherein the repetition times are not less than 10 times, and the calculating module can calculate the k1 value of the dust meter according to the condition that the delta m is 1/k ln (N1/N2);
(8) the standard membrane is changed to have a mass of 0.6mg/cm2Repeating (3) to (6) to obtain k 2;
(9) the standard membrane is changed to have a mass of 0.9mg/cm2Repeating (3) to (6) to obtain k 3;
(10) calculating the average value k of k1 and k2 by using the calculation module12And the average value k of k2 and k323。
k1 is less than 0.3mg/cm2Fractional correction factor of, k12Is 0.3-0.6mg/cm2Fractional correction factor of, k23Is 0.6-0.9mg/cm2The coefficient of segmental correction of (k 3) is > 0.9mg/cm2And writing the segmented correction coefficient into the dust meter to serve as a working parameter of the dust meter.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (2)
1. The calibration system of the beta absorption type dust measuring instrument is characterized by comprising a standard membrane support for loading standard membranes with different masses, a working filter belt, a counting module, a storage module and a calculation module; the mass of the standard diaphragm with different masses is not more than 1.2mg/cm2；
The counting module is used for counting the pulse frequency of a beta radioactive source of the beta absorption type dust meter passing through a blank working filter belt or a working filter belt tightly attached to a standard membrane, and the total counting amount is respectively recorded as N1 and N2; and for calculating an average of N1 and N2 using the data stored in the storage module, and then calculating a k value by an average of the formulas Δ m =1/k ln (N1/N2), N1 and N2;
the storage module is used for storing the mass Δ m of the standard membrane and the N1 and N2 obtained by the counting module;
the calculating module is used for calculating a k value by using the data stored by the storage module according to a formula of Δ m =1/k ln (N1/N2); and the average value of k values of the standard diaphragms with different adjacent qualities is calculated to be used as a sectional correction coefficient; the different quality standard membrane is 0.3 mg/cm2Then k1 value and 0.6mg/cm are obtained by calculation2Then k2 value or 0.9mg/cm is obtained by calculation2Obtaining a k3 value through calculation; calculate the average k of k1 and k212The average value k of k2 and k3 is calculated23(ii) a The k1 is less than 0.3mg/cm2The piecewise correction coefficient of, said k12Is 0.3-0.6mg/cm2The piecewise correction coefficient of, said k23Is 0.6-0.9mg/cm2The k3 is more than 0.9mg/cm2The segment correction coefficient of (1);
when the working filter belts tightly attached to the standard membranes are counted, the standard membranes with different masses of the standard membrane support tightly attach to the upper portions of the working filter belts so as to fix the working filter belts, and the distance between the standard membranes and the working filter belts is less than or equal to 0.3 mm.
2. A method of using the targeting system of claim 1, the method comprising:
(1) the storage module stores standard diaphragm masses Δ m of different masses of the standard diaphragm support;
(2) counting the pulse frequency of a beta radioactive source of the beta absorption type dust measuring instrument passing through the blank working filter belt by adopting the counting module, wherein the total counting amount is N1, and N1 is stored in the storage module; the counting time is 6 minutes;
(3) tightly attaching standard membranes with different masses of the standard membrane support above the counting position of the blank working filter belt, wherein the distance between the standard membranes and the counting position of the blank working filter belt is less than or equal to 0.3 mm;
(4) counting the pulse frequency of a beta radioactive source of the beta absorption type dust measuring instrument passing through the working filter belt tightly attached to the standard membrane by adopting the counting module, wherein the total counting amount is N2, and N2 is stored in the storage module; the counting time is 6 minutes;
(5) repeating the steps (2) to (4) to obtain a plurality of total counting amounts N1 and N2, storing the total counting amounts into the storage module, wherein the number of times of repetition is not less than 10, and the calculating module calculates the average number of the total counting amounts N1 and N2 respectively;
calculating k values by using the calculation module through the average of the formulas Δ m =1/k ln (N1/N2), N1 and N2;
(6) the mass of the standard membrane is 0.3mg/cm2Repeating the steps (1) to (5) to obtain a k1 value;
the mass of the standard membrane is 0.6mg/cm2Repeating the steps (1) to (5) to obtain a k2 value;
the mass of the standard membrane is 0.9mg/cm2Repeating the steps (1) to (5) to obtain a k3 value;
calculating the average value k of k1 and k2 by using the calculation module12And the average value k of k2 and k323；
k1 is less than 0.3mg/cm2Fractional correction factor of, k12Is 0.3-0.6mg/cm2Fractional correction factor of, k23Is 0.6-0.9mg/cm2The coefficient of segmental correction of (k 3) is > 0.9mg/cm2The piecewise correction coefficient of (1).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS58160806A (en) * | 1982-03-17 | 1983-09-24 | Denki Kagaku Keiki Co Ltd | Dust meter |
| JPS58160807A (en) * | 1982-03-17 | 1983-09-24 | Denki Kagaku Keiki Co Ltd | Beta ray transmission type dust meter |
| CN203561570U (en) * | 2013-11-23 | 2014-04-23 | 安徽蓝盾光电子股份有限公司 | Atmospheric particulate monitor calibration device based on beta ray method |
| CN104655534A (en) * | 2013-11-23 | 2015-05-27 | 安徽蓝盾光电子股份有限公司 | Device for calibrating beta ray method-based atmospheric particulate monitor |
| CN103913406B (en) * | 2014-04-04 | 2016-01-27 | 北京西山新干线环保设备有限公司 | The absorption dust gauge automatic marking method of β |
| CN107063954B (en) * | 2017-04-12 | 2019-08-06 | 北京雪迪龙科技股份有限公司 | A kind of method that error correction control system, β dust gauge eliminate strainer error |
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