Method for multi-gas measurement based on gfc wheels

Abstract

The present application relates to absorption spectroscopy technology, and specifically provides a multi-gas measurement method based on GFC wheel, comprising the following steps: A1. obtaining standard deviation R of reference signal in multiple detection periods rsd and standard deviation M of measurement signal rsd ; A2. obtaining offset parameter K=f(R rsd , M rsd , t) according to the standard deviations, t is the absolute value of the difference between the rotation period at the last calibration and the current rotation period; A3. comparing the offset parameter K with a set range; if the offset parameter K is normal, no adjustment is needed; if the offset parameter K is abnormal, corresponding adjustment measures are implemented according to the set range where the offset parameter K is located, and the adjustment measures comprise: obtaining complete reference signal and measurement signal, thereby obtaining Δt, and replacing. The present application has the advantages of accurate measurement and the like.

Description

Technical Field

[0001] This invention relates to absorption spectroscopy, and more particularly to a multi-gas measurement method based on a GFC wheel. Background Technology

[0002] In multi-gas detection, GFC wheels are often used. GFC wheels are generally controlled by MCUs to complete the acquisition and processing of photoelectric signals. The following technical solutions are commonly used at present.

[0003] 1. Sampling is completed by identifying each acquisition time parameter through multiple photoelectric switches or by manually configuring each device. The drawback is that: Multi-channel photoelectric switch solutions have high requirements for the accuracy of hardware structure assembly position, are complex to assemble, and have high requirements for the real-time performance of the signal acquisition system, which can easily lead to missed data acquisition.

[0004] Manually configuring sampling timing parameters is not feasible because the parameters cannot be fixed. Due to differences in different batches or production assembly processes, each unit requires manual inspection using an oscilloscope to check whether the sampling point is centered, resulting in a large workload and low efficiency.

[0005] 2. Add a CPLD specifically for complete waveform acquisition, followed by peak finding calculation. The drawback of this approach is: It requires the addition of a dedicated CPLD chip for signal acquisition and processing, which increases hardware costs, increases the amount of data computation, and complicates software algorithms. Summary of the Invention

[0006] To address the shortcomings of the existing technical solutions, this invention provides a multi-gas measurement method based on a GFC wheel.

[0007] The objective of this invention is achieved through the following technical solution: A multi-gas measurement method based on a GFC wheel includes data acquisition, in which the measurement light passes through a reference cell and a measurement cell corresponding to the gas to be measured on the GFC wheel in a time-division manner to obtain a reference signal and a measurement signal. The measurement light passes through a chopper before or after passing through the GFC wheel. The measurement method also includes the following steps: A1. Obtain the relative standard deviation R of the reference signal within multiple detection cycles. rsd The mean of the reference signal R_avg and the relative standard deviation M of the measured signal rsd ; A2. Obtain the offset parameter K=f(R) based on the relative standard deviation. rsd M rsd ,R_avg,t), where t is the absolute value of the difference between the rotation period at the last calibration and the current rotation period; A3. Compare the offset parameter K with the set range; If the offset parameter K is normal, no adjustment is needed; If the offset parameter K is abnormal, corresponding adjustment measures are implemented according to the set range in which the offset parameter K is located. The adjustment measures include: obtaining a complete reference signal and measurement signal to obtain Δt, and replacing it.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Signal acquisition via dual channels (first channel and second channel). The first channel (main channel) acquires signals based on precise delay + hardware interpolation method, which simplifies the signal acquisition process, reduces the computational requirements of the MCU processor, improves timing accuracy, and ensures the real-time performance of signal acquisition.

[0009] The second channel (reference channel) briefly intervenes in full waveform acquisition, enabling efficient acquisition of square wave signals, reducing MCU computational requirements, eliminating the need for manual parameter adjustment, and greatly improving production efficiency and acquisition accuracy.

[0010] 2. An adaptive mechanism based on the offset coefficient evaluation algorithm automatically updates the sampling timing parameters without the need for manual calibration, thus improving efficiency.

[0011] It automatically calculates the rotation cycle in real time, analyzes the trend of motor speed change, and dynamically fine-tunes the sampling timing to ensure accurate and reliable sampling. Attached Figure Description

[0012] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings: Figure 1 This is a flowchart illustrating a measurement method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the signals acquired according to an embodiment of the present invention; Figure 3 The data sequence S obtained according to the embodiments of the present invention i ; Figure 4 It is the binarized sequence M obtained according to an embodiment of the present invention. Detailed Implementation

[0013] Figures 1-4The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to explain the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the optional embodiments described below, but is defined only by the claims and their equivalents.

[0014] Example 1

[0015] The multi-gas measurement method based on the GFC wheel in this invention includes data acquisition. In the data acquisition, the measurement light passes through the reference cell and the measurement cell corresponding to the gas to be measured on the GFC wheel in a time-division manner. The first channel obtains the reference signal and the measurement signal. The measurement light passes through the chopper before or after passing through the GFC wheel.

[0016] like Figure 1 As shown, the measurement method further includes the following steps: A1. Obtain the relative standard deviation R of the reference signal within multiple detection cycles. rsd The mean of the reference signal R_avg and the relative standard deviation M of the measured signal rsd .

[0017] A2. Obtain the offset parameter K=f(R) based on the relative standard deviation. rsd M rsd ,R_avg,t), where t is the absolute value of the difference between the rotation period at the last calibration and the current rotation period.

[0018] A3. Compare the offset parameter K with the set range.

[0019] If the offset parameter K is normal, no adjustment is needed.

[0020] If the offset parameter K is abnormal, corresponding adjustment measures are implemented according to the set range in which the offset parameter K is located. The adjustment measures include: obtaining a complete reference signal and measurement signal to obtain Δt, and replacing it.

[0021] To accommodate a reasonable adjustment method, further, if the offset parameter K is less than the first threshold, no adjustment is required.

[0022] If the offset parameter is between the first threshold and the second threshold, replace the original Δt with Δt·T0 / T1; T0 is the rotation period of the previous GFC wheel calibration, and T1 is the rotation period of the current GFC wheel; the second threshold is greater than the first threshold.

[0023] If the offset parameter is greater than the second threshold, the second channel obtains the complete reference signal and measurement signal, thereby obtaining a new Δt and replacing the original Δt.

[0024] To obtain an accurate Δt, the method for obtaining Δt is further as follows: The GFC wheel rotates for N cycles, and the second channel (only one of the first and second channels can work at a time, not both) collects all data within the cycle, resulting in sequence S. i , i=1,2···N.

[0025] Sequence S i Divide the sample into 2A portions, where A is the number of different types of gases to be tested. For each portion, find the maximum value V. max and minimum value V min The threshold D is obtained as (V max +V min ) / 2, resulting in 2A thresholds.

[0026] For sequence S i For each sample, a difference is calculated with the corresponding threshold. If the difference is less than the threshold, the result is assigned 0; if it is greater than the threshold, the result is assigned 1.

[0027] Edge detection is performed to obtain a list of edges. The order and number of edges are verified (4A·B), and they are arranged in alternating ascending and descending order.

[0028] Pair the edges sequentially to form (2A·B) square waves, each with a start and an end edge. Calculate the time Δt from the start and end positions of the square waves to the center position of the first square wave.

[0029] To reduce hardware requirements, further, during data acquisition, within each cycle T, the GFC wheel starts rotating from its initial position. After an interval Δt, the first channel begins acquiring data for the reference signal or measurement signal. Subsequently, data is acquired every time interval ΔT = T / (4A·B), thereby obtaining (A·B) reference signals R and (A·B) measurement signals M; A is the number of types of gas to be measured, B is the number of equal divisions of the chopper corresponding to the reference cell or measurement cell, and T is the rotation cycle of the GFC wheel.

[0030] To obtain an accurate initial position, the GFC wheel further reaches its initial position when the flag of the chopper or GFC wheel reaches the recognition position. For example, the flag is a protrusion, and a photoelectric switch is located at the recognition position.

[0031] To accurately reflect the deviation, the offset parameter K is further defined as follows: K=f(R rsd M rsd ,R_ avg,Δt)=α·(R rsd +M rsd )+β·R md +γ·exp(θ·t).

[0032] R md =abs(1-R_ avg / R0).

[0033] α is the signal stability weighting factor, β is the basic weighting of the value deviation, γ is the speed deviation sensitivity coefficient, θ is the basic weighting of the speed deviation, and R_ avg R0 is the average value of the current reference signal, and R0 is the average value of the reference signal obtained during calibration.

[0034] Example 2

[0035] An application example of the multi-gas measurement method based on a GFC wheel according to Embodiment 1 of the present invention.

[0036] In this application example, two gases are detected, each with a corresponding reference cell (filled with a high concentration of the gas to be tested) and a measurement cell (filled with nitrogen). That is, there are four reference cells and measurement cells evenly distributed on the GFC wheel.

[0037] The chopper is divided into 12 equal parts, meaning that each reference cell and measurement cell corresponds to 3 equal parts.

[0038] The chopper has a protrusion that serves as a marker. When the protrusion reaches and is recognized by the photoelectric switch at the recognition position, the GFC wheel is in its initial position.

[0039] like Figure 1 As shown, the measurement method further includes the following steps: A1. In data acquisition, within each cycle T, the GFC wheel starts rotating from its initial position. After an interval Δt, the first channel begins acquiring data for the reference signal or the measurement signal. Subsequently, data is acquired at intervals ΔT = T / (4A·B) (pulse-type acquisition, non-continuous acquisition), thus obtaining (A·B) reference signals R and (A·B) measurement signals M; A = 2, B = 3, and T is the rotation cycle of the GFC wheel. For example... Figure 2 As shown.

[0040] The data is presented in three sets: one factor correct, slight deviation, and deviation margin. Please see Table 1 for details.

[0041] Table 1 shows the measurement signal M and the reference signal R.

[0042] .

[0043] Obtain the standard deviation R of the reference signal within multiple detection cycles rsdThe reference signal mean R_avg and the standard deviation M of the measured signal rsd .

[0044] A2. Obtain the offset parameter K based on the standard deviation.

[0045] K=f(R rsd M rsd ,R_ avg ,Δt)=0.8·(R rsd +M rsd )+2.5·R md +0.4·exp(0.95·t).

[0046] R md =abs(1-R_ avg / R0).

[0047] R in normal sampling data md =0.0002, t=0.2ms, so K=0.55.

[0048] R in slightly off-sampled data md =0.01, t=1ms, so K=1.4.

[0049] R in off-sampled data md =0.435, t=1.6ms, so K=3.38.

[0050] A3. Compare the offset parameter K with the set range.

[0051] If the offset parameter K is less than the first threshold of 1.0, no adjustment is needed.

[0052] If the offset parameter is between the first threshold and the second threshold, replace Δt with Δt·T0 / T1; T0 is the rotation period of the last GFC wheel calibration, and T1 is the rotation period of the current GFC wheel; the second threshold is greater than the first threshold.

[0053] If the offset parameter is greater than the second threshold of 1.8, the second channel obtains the complete reference signal and measurement signal, thereby obtaining Δt, and then replacing it. The specific method for obtaining Δt is as follows: The GFC wheel rotates for N=10 cycles. The second channel (only one of the first and second channels can work at a time, not both) collects all data within the cycle and performs smoothing and noise reduction processing to obtain the data sequence S. i i=1,2···N, sampling frequency 30kHz, 1 point corresponds to 1 / 30ms, such as Figure 3 As shown.

[0054] S iDivide the data into two parts. Find the maximum and minimum values ​​for points 1-500 in the first part and 550-1000 in the second part respectively to obtain the threshold values, as shown in Table 2.

[0055] Table 2 shows the obtained maximum, minimum, and threshold values.

[0056] .

[0057] For sequence S i Each sample is compared with its corresponding threshold; if the difference is less than the threshold, it is assigned 0; if it is greater than the threshold, it is assigned 1, resulting in the binarized sequence M. Figure 4 As shown.

[0058] Edge detection is performed, with 0->1 being a rising edge and 1->0 being a falling edge. The number and sequence of edges are checked and matched to obtain 6 square waves. The position of the first square wave is 43-129, and the center position of the square wave is 86. The initial reset signal is init until the center position of the first square wave is 86, so Δt = 86·1 / 30 = 2.87ms can be obtained. For specific data, please see Table 3.

[0059] Table 3 shows the intermediate data.

[0060] .

[0061] Based on the data location information, the average value R0 of the reference signal after this calibration and the current rotational speed T0 can be calculated. Further analysis can be performed on the position of each square wave in each revolution to accurately adjust the sampling timing.

Claims

1. A multi-gas measurement method based on a GFC wheel, comprising data acquisition, wherein in the data acquisition, the measuring light sequentially passes through a reference cell and a measurement cell corresponding to the gas to be measured on the GFC wheel, and a first channel obtains the reference signal and the measurement signal; characterized in that, The measurement method further includes the following steps: A1. Obtain the relative standard deviation R of the reference signal within multiple detection cycles. rsd The mean of the reference signal R_avg and the relative standard deviation M of the measured signal rsd ; A2. Obtain the offset parameter K=f(R) based on the relative standard deviation. rsd M rsd ,R_avg,t), where t is the absolute value of the difference between the rotation period at the last calibration and the current rotation period; A3. Compare the offset parameter K with the set range; If the offset parameter K is normal, no adjustment is needed; If the offset parameter K is abnormal, corresponding adjustment measures are implemented according to the set range in which the offset parameter K is located. The adjustment measures include: obtaining a complete reference signal and measurement signal to obtain a new Δt and replacing it.

2. The measurement method according to claim 1, characterized in that, If the offset parameter K is less than the first threshold, no adjustment is needed; If the offset parameter is between the first threshold and the second threshold, replace the original Δt with Δt·T0 / T1; T0 is the rotation period of the last GFC wheel calibration, and T1 is the rotation period of the current GFC wheel. The second threshold is greater than the first threshold; If the offset parameter is greater than the second threshold, the second channel obtains the complete reference signal and measurement signal, thereby obtaining a new Δt and replacing it.

3. The measurement method according to claim 2, characterized in that, The method to obtain Δt is as follows: The GFC wheel rotates for N cycles, and all data within each cycle is collected to obtain sequence S. i , i = 1, 2, ..., N; Sequence S i Divide the sample into 2A portions, where A is the number of different types of gases to be tested. For each portion, find the maximum value V. max and minimum value V min The threshold D is obtained as (V max +V min ) / 2, resulting in 2A thresholds; For sequence S i Each sample is compared with the corresponding threshold value; if the difference is less than the threshold, it is assigned 0; if the difference is greater than the threshold, it is assigned 1. Edge detection is performed to obtain a list of edges. The order and number of edges are verified (4A·B), and they are arranged in alternating ascending and descending order. Pair the edges sequentially to form (2A·B) square waves, each with a start and an end edge. Calculate the time Δt from the start and end positions of the square waves to the center position of the first square wave.

4. The measurement method according to claim 3, characterized in that, The first and second channels do not operate simultaneously.

5. The measurement method according to claim 2, characterized in that, The first threshold is 1, and the second threshold is 1.

8.

6. The measurement method according to claim 1, characterized in that, During data acquisition, within each cycle T, the GFC wheel starts rotating from its initial position. After an interval of Δt, the first channel begins to acquire data of the reference signal or the measurement signal. Subsequently, data is acquired every time interval ΔT=T / (4A·B), thereby obtaining (A·B) reference signals R and (A·B) measurement signals M. A is the number of types of gas to be measured, B is the number of equal divisions of the chopper corresponding to the reference cell or the measurement cell, and T is the rotation cycle of the GFC wheel.

7. The measurement method according to claim 6, characterized in that, When the flag bit of the chopper or GFC wheel reaches the recognition bit, the GFC wheel reaches its initial position.

8. The measurement method according to claim 7, characterized in that, The marker is a protrusion, and the photoelectric switch is located at the identification position.

9. The measurement method according to claim 1, characterized in that, The offset parameter K is: K=f(R rsd , M rsd ,R_ avg ,Δt)=α·(R rsd +M rsd )+β·R md +γ·exp(θ·t); R md =abs(1-R_ avg / R0); α is the signal stability weighting factor, β is the basic weighting of the value deviation, γ is the speed deviation sensitivity coefficient, θ is the basic weighting of the speed deviation, and R_ avg R0 is the average value of the current reference signal, and R0 is the average value of the reference signal obtained during calibration.

10. The measurement method according to claim 9, characterized in that, α=0.8, β=2.5, γ=0.4, θ=0.95.

Images