Calibration method of laser methane sensor

Abstract

The invention discloses a calibration method of a laser methane sensor, which comprises the following steps: a, pre-calibration: calibrating a reading corresponding to the detector output x of the laser methane sensor to be calibrated as y, the reading being a display value of the laser methane sensor to be calibrated; b, fixed-point calibration: respectively adopting standard methane concentration gases with the concentrations of yi and yj for fixed-point calibration; c, verifying; d, carrying out segmented calibration; and e, circulating or ending. Wherein the zero point and full scale calibration of the laser methane sensor is carried out during pre-calibration, and the calibration is carried out by adopting standard methane concentration gas of each concentration point. According to the invention, the problem of linearity of the laser methane sensor can be effectively solved, and the measurement precision of the laser methane sensor is improved.

Description

Technical Field

[0001] The present invention relates to sensor technology, and in particular to a calibration method for a laser methane sensor. Background Art

[0002] The operating principle of a laser methane sensor is based on laser absorption spectroscopy. It consists of a laser source, a sample chamber, and a detector. The laser source emits a laser beam of a specific wavelength. After passing through the sample chamber, part of the laser light is absorbed by methane molecules, while the remainder is received by the detector. The detector measures the absorbed laser energy and, based on the relationship between the absorbed laser light and the concentration of methane molecules, calculates the methane concentration in the atmosphere. The absorbed laser light is directly proportional to the methane concentration. However, due to variations in the detector and its processing circuitry, as well as environmental factors, the entire measurement range of the laser methane sensor is not completely linear. Therefore, linear calibration of the laser methane sensor can result in significant errors. Summary of the Invention

[0003] To overcome the above problems, the present invention aims to provide a calibration method for a laser methane sensor, which can effectively solve the linearity problem of the laser methane sensor and improve the measurement accuracy of the laser methane sensor.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for calibrating a laser methane sensor comprises the following steps:

[0006] a. Pre-calibration: Calibrate the reading corresponding to the detector output x of the laser methane sensor to be calibrated to y. The reading is the display value of the laser methane sensor to be calibrated. y is determined by the following formula:

[0007]

[0008] Among them, x0 is the output value of the laser methane sensor to be calibrated when it corresponds to clean air, y max is the full scale degree of the laser methane sensor to be calibrated, x max The laser methane sensor to be calibrated corresponds to a methane concentration of y max The output value of the detector;

[0009] The accumulator is cleared;

[0010] b. Fixed-point calibration: use concentration y i 、y j Fixed-point calibration of standard methane concentration gas, 0≤y i <y j ≤y max , the calibration reading is y i 、yj , and read the output x corresponding to the detector i 、x j ;

[0011] The calibration reading is y i 、y j The readings between are as follows:

[0012]

[0013] Where y is the reading and x is the output of the detector;

[0014] The accumulator is incremented by 1;

[0015] c. Verification: Using a concentration of y k Standard methane concentration gas fixed point verification, y i <y k <y max , get the reading y k1 and the detector output x k , compare y k with y k1 ;

[0016] When y k with y k1 When the difference is not greater than the first predetermined value, execute step e;

[0017] When y k with y k1 When the difference is greater than a first predetermined value, execute step d;

[0018] d. Segment calibration: Clear the accumulator and calibrate the output x of the detector. k The corresponding reading is y k ; And the segmented calibration is as follows:

[0019]

[0020] e. Loop or end: Compare the value of the accumulator with the third predetermined value. When the value of the accumulator is less than the third predetermined value, change y i 、y j , execute step d;

[0021] When the value of the accumulator reaches a third predetermined value, calibration is completed.

[0022] Furthermore, step a also includes zero point calibration and full scale calibration;

[0023] The zero point calibration includes: using clean air to calibrate the zero point, reading the zero point output value x of the detector of the laser methane sensor to be calibrated o , will be the zero output value x oThe corresponding reading is calibrated to 0, and the reading is the display value of the laser methane sensor to be calibrated;

[0024] The full-scale calibration includes: using a concentration of y max The full scale of the standard methane concentration gas is calibrated, y max The full-scale reading of the laser methane sensor to be calibrated is x, which is the full-scale output value of the detection. max , will be with the full-scale output value x max The corresponding reading is calibrated as y max .

[0025] Preferably, when the clean air is used to calibrate the zero point, the clean air is poured into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time. The zero point output value x o is the average value;

[0026] The concentration used is y max When the full scale is calibrated with the standard methane concentration gas, the laser to be calibrated will have a methane concentration of y max The standard methane concentration gas is injected into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time. The full-scale output value x max is the average value.

[0027] Further preferably, the average value is the arithmetic mean obtained after eliminating abnormal data.

[0028] Preferably, in both step b and step c, standard methane concentration gas corresponding to the methane concentration is injected into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time.

[0029] Preferably, x i 、x j 、x k 、y k1 All are arithmetic means after excluding outliers.

[0030] Preferably, steps a to e are performed at room temperature.

[0031] The present invention adopts a segmented calibration method to calibrate the laser methane sensor, which can effectively overcome the linear error of the laser methane sensor and improve the measurement accuracy and stability of the laser methane sensor.

[0032] The present invention can select different y i 、y j After several cycles, the entire measurement range is covered, and multiple linear segments within the full range are used to approximate the true methane concentration, thereby improving the measurement accuracy. i 、y jThe smaller the interval, the higher the measurement accuracy achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the flow of the calibration method disclosed in the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, this embodiment discloses a calibration method for a laser methane sensor, including:

[0036] Step a, pre-calibration: calibrate the reading corresponding to the detector output x of the laser methane sensor to be calibrated to y, where the reading is the display value of the laser methane sensor to be calibrated, and y is determined by the following formula:

[0037]

[0038] Among them, x0 is the output value of the laser methane sensor to be calibrated when it corresponds to clean air, y max is the full scale degree of the laser methane sensor to be calibrated, x max The laser methane sensor to be calibrated corresponds to a methane concentration of y max The output value of the detector.

[0039] And the accumulator is cleared to zero. The accumulator is used to record the number of cycles of the segmented calibration described below. The required number of cycles can be set according to the specific situation.

[0040] Step a also completes the zero point and full scale calibration of the laser methane sensor, as follows:

[0041] Zero point calibration includes: using clean air to calibrate the zero point. Specifically, clean air is poured into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time. The zero point output value x of the detector of the laser methane sensor to be calibrated is read. o , will be the zero output value x o The corresponding reading is calibrated to 0, and the reading is the display value of the laser methane sensor to be calibrated.

[0042] Full scale calibration includes: using a concentration of y max The full scale is calibrated with the standard methane concentration gas. Specifically, the methane concentration of the laser to be calibrated is y max The standard methane concentration gas is injected into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time, y max The full-scale reading of the laser methane sensor to be calibrated is x, which is the full-scale output value of the detection.max , will be with the full-scale output value x max The corresponding reading is calibrated as y max .

[0043] In this embodiment, x o 、x max is the arithmetic mean after removing abnormal data. During the maintenance time, x o 、x max It is possible to obtain multiple values, and the above arithmetic mean can reduce the measurement error to a certain extent.

[0044] b. Fixed-point calibration: use concentration y i 、y j Fixed-point calibration of standard methane concentration gas, 0≤y i <y j ≤y max , the calibration reading is y i 、y j , and read the output x corresponding to the detector i 、x j ;

[0045] The calibration reading is y i 、y j The readings between are as follows:

[0046]

[0047] Where y is the reading and x is the output of the detector;

[0048] The accumulator is incremented by 1;

[0049] c. Verification: Using a concentration of y k Standard methane concentration gas fixed point verification, y i <y k <y max , get the reading y k1 and the detector output x k , compare y k with y k1 ;

[0050] When y k with y k1 When the difference is not greater than the first predetermined value, execute step e;

[0051] When y k with y k1 When the difference is greater than a first predetermined value, execute step d;

[0052] d. Segment calibration: Clear the accumulator and calibrate the output x of the detector. k The corresponding reading is yk ; And the segmented calibration is as follows:

[0053]

[0054] e. Loop or end: Compare the value of the accumulator with the third predetermined value. When the value of the accumulator is less than the third predetermined value, change y i 、y j , execute step d;

[0055] When the value of the accumulator reaches a third predetermined value, calibration is completed.

[0056] Similar to zero-point and full-scale calibrations, the above process involves injecting a standard methane concentration into the sample chamber of the laser methane sensor to be calibrated and maintaining the concentration for a predetermined period of time. The measured values ​​are the arithmetic mean after eliminating abnormal data.

[0057] The present invention can select different y i 、y j After several cycles, the entire measurement range is covered, and multiple linear segments within the full range are used to approximate the true methane concentration, thereby improving the measurement accuracy. i 、y j The smaller the interval, the higher the measurement accuracy achieved.

[0058] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A calibration method for a laser methane sensor, characterized in that: The following steps are involved: a. Pre-calibration: Calibrate the reading corresponding to the detector output x of the laser methane sensor to be calibrated to y. The reading is the display value of the laser methane sensor to be calibrated. y is determined by the following formula: Among them, x0 is the output value of the laser methane sensor to be calibrated when it corresponds to clean air, y max is the full scale degree of the laser methane sensor to be calibrated, x max The laser methane sensor to be calibrated corresponds to a methane concentration of y max The output value of the detector; The accumulator is cleared; b. Fixed-point calibration: use concentration y i 、y j Fixed-point calibration of standard methane concentration gas, 0≤y i <y j ≤y max , the calibration reading is y i 、y j , and read the output x corresponding to the detector i 、x j ; The calibration reading is y i 、y j The readings between are as follows: Where y is the reading and x is the output of the detector; The accumulator is incremented by 1; c. Verification: Using a concentration of y k Standard methane concentration gas fixed point verification, y i <y k <y max , get the reading y k1 and the detector output x k , compare y k with y k1 ; When y k with y k1 When the difference is not greater than the first predetermined value, execute step e; When y k with y k1 When the difference is greater than a first predetermined value, execute step d; d. Segment calibration: Clear the accumulator and calibrate the output x of the detector. k The corresponding reading is y k ; And the segmented calibration is as follows: e. Loop or end: Compare the value of the accumulator with the third predetermined value. When the value of the accumulator is less than the third predetermined value, change y i 、y j , execute step d; When the value of the accumulator reaches a third predetermined value, calibration is completed.

2. The laser methane sensor calibration method according to claim 1, characterized in that: Step a also includes zero point calibration and full scale calibration; The zero point calibration includes: using clean air to calibrate the zero point, reading the zero point output value x of the detector of the laser methane sensor to be calibrated o , will be the zero output value x o The corresponding reading is calibrated to 0, and the reading is the display value of the laser methane sensor to be calibrated; The full-scale calibration includes: using a concentration of y max The full scale of the standard methane concentration gas is calibrated, y max The full-scale reading of the laser methane sensor to be calibrated is x, which is the full-scale output value of the detection. max , will be with the full-scale output value x max The corresponding reading is calibrated as y max .

3. The laser methane sensor calibration method according to claim 2, characterized in that: When the clean air is used to calibrate the zero point, the clean air is poured into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time. The zero point output value x o is the average value; The concentration used is y max When the full scale is calibrated with the standard methane concentration gas, the laser to be calibrated will have a methane concentration of y max The standard methane concentration gas is injected into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time. The full-scale output value x max is the average value.

4. The laser methane sensor calibration method according to claim 3, characterized in that: The average value is the arithmetic mean obtained after eliminating abnormal data.

5. The laser methane sensor calibration method according to any one of claims 1 to 4, characterized in that: In both step b and step c, standard methane concentration gas corresponding to the methane concentration is injected into the sample chamber of the laser methane sensor to be calibrated and maintained for a predetermined time.

6. The laser methane sensor calibration method according to claim 5, characterized in that: x i 、x j 、x k 、y k1 All are arithmetic means after excluding outliers.

7. The laser methane sensor calibration method according to claim 5, characterized in that: Steps a to e are carried out at room temperature.

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