A batch compensation method for thermal conductivity helium sensor

Abstract

The present invention discloses a batch compensation method for a thermal conductivity helium sensor, comprising the following steps: selecting one of the sensors as a standard sensor, setting TREF, and measuring its LUT_C, LUT_AH and LUT_T; obtaining S and ADC_0 of all sensors through ventilation tests; writing the S and ADC_0 data of the sensors into the corresponding sensors; batch compensation of the sensors can be achieved through a small number of tests. For thermopiles, the change in the temperature difference between the hot and cold ends can be approximately considered to be proportional to the change in the thermal conductivity of the gas environment. Since the water vapor concentration needs to consider the atmospheric pressure, and most occasions are at standard atmospheric pressure, it is replaced by the absolute humidity associated therewith. The batch compensation method for a thermal conductivity helium sensor described in the present invention can realize the temperature and humidity compensation of the thermal conductivity helium sensor, and batch calibration can be achieved by only a small number of tests, with low test costs and simple processes.

Description

Technical Field

[0001] The invention relates to the field of helium concentration detection, and in particular to a batch compensation method for a thermal conductivity helium sensor. Background Art

[0002] The batch compensation method of thermal conductivity helium sensor is a method for helium concentration detection. In the field of gas concentration detection, thermal conductivity gas sensor has the characteristics of large range and long service life. Thermal conductivity gas sensor is usually composed of heating device and temperature sensitive device. The heating device transfers heat to the temperature sensitive element. The temperature sensitive element is in the background gas environment and transfers heat to the gas environment. When the gas to be measured enters the background gas environment, the thermal conductivity of the gas environment changes, which changes the heat transfer rate of the temperature sensitive element, resulting in temperature changes. The size and direction of the change depend on the thermal conductivity relationship between the gas to be measured and the background gas. In helium measurement, the background gas is usually dry nitrogen. The heating element is usually a heating resistor, and the temperature sensitive device is usually a temperature sensitive resistor or a thermopile. Compared with the temperature sensitive resistor, the thermopile does not require external power excitation when working, and the output signal is proportional to the temperature difference between its hot and cold ends, and the related signal circuit is relatively simple. Since the sensitivity of the thermopile is affected by temperature and has a temperature coefficient, temperature drift will occur. At the same time, there is a certain amount of water vapor in the actual gas, which will also cause drift. In order to achieve accurate measurement of helium, temperature and humidity compensation is required. With the continuous development of science and technology, people have higher and higher process requirements for batch compensation methods of thermal conductivity helium sensors.

[0003] The existing batch compensation method of thermal conductivity helium sensors has certain drawbacks when used. For drift caused by temperature, two approximately identical sensors are usually used, one of which is placed in a sealed package filled with background gas. The output signals of the two are differentially output, which can reduce zero drift to a certain extent, but cannot avoid the influence of humidity, and the hardware cost is relatively high.

[0004] Another method is to perform multivariable tests on each sensor to obtain the relationship between the output signal and temperature, humidity, and helium concentration, and perform compensation based on this relationship. This method can achieve accurate temperature and humidity compensation, but it requires a large number of tests and is not suitable for batch calibration. For this reason, we propose a batch compensation method for thermal conductivity helium sensors. Summary of the invention

[0005] Technical problem solved: In view of the shortcomings of the prior art, the present invention provides a batch compensation method for a thermal conductivity helium sensor, which can realize temperature and humidity compensation of the thermal conductivity helium sensor. Only a small amount of testing is required to achieve batch calibration, with low test cost and simple process, which can effectively solve the problems in the background technology.

[0006] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is: a batch compensation method for thermal conductivity helium sensor, comprising the following steps:

[0007] S1: Select one of the sensors as the standard sensor, set TREF, and measure its LUT_C, LUT_AH and LUT_T;

[0008] S2: Obtain S and ADC_0 of all sensors through ventilation test;

[0009] S3: Write the sensor's S and ADC_0 data into the corresponding sensor;

[0010] S4: Bulk compensation of sensors can be achieved with a small number of experiments.

[0011] As a preferred technical solution of the present application, for the thermopile, the change in the temperature difference between the hot and cold ends can be approximately considered to be proportional to the change in the thermal conductivity of the gas environment, and the average thermal conductivity of the gas environment is:

[0012] λ x =λ He C He +λ H2O C H2O +λ N2 C N2

[0013] where λ He , H2O , N2 is the thermal conductivity of helium, water vapor, and nitrogen, C HE , C N2 , C H2O The concentrations of helium, nitrogen and water vapor are calculated. Since the water vapor concentration needs to take the atmospheric pressure into consideration and most of the time it is at standard atmospheric pressure, it will be replaced by the absolute humidity associated with it.

[0014] As a preferred technical solution of the present application, since the thermopile sensitivity coefficient is related to temperature, its temperature coefficient is TC, then: f1(C He , T) = f1(C He , T REF )×(1+TC×(TT REF ))

[0015] Where T REF is the reference temperature, which is determined by the tester. H2O , T), since the thermopile temperature coefficient TC is small, to simplify the steps, it can be considered that the effect of humidity on the thermopile output is independent of temperature.

[0016] As a preferred technical solution of the present application, one helium sensor is selected as a standard sensor, and f1(C He , T REF ), offset1, oTfset2 methods.

[0017] As a preferred technical solution of the present application, for f1(C He , T REF ), if the sensor range is 0~FS, then:

[0018] In the background dry gas, the ambient temperature is T REF Under the condition of REF );

[0019] The dry helium concentration is The ambient temperature is T REF Under the condition of

[0020] When the dry helium concentration is FS and the ambient temperature is T REF Under the condition of REF );

[0021] According to f1(0, T REF ), f1(FS,T REF ) to perform nonlinear interpolation and obtain the interpolation table LUT_C (C He ), and then through linear interpolation, LUT_C(C He ) is approximately equal to f1(C He , T REF ).

[0022] As a preferred technical solution of the present application, for offset1(AH)

[0023] According to the accuracy requirements, select several absolute humidity points and perform nonlinear interpolation to obtain the interpolation table LUT_AH0 (AH). Assume that the absolute humidity points selected are AH0, AH1, and AH2.

[0024] Water vapor is introduced into the background gas, and the required absolute humidity AH is obtained according to the temperature T and relative humidity RH;

[0025] For lUT_AH(C H2O ) can be approximately equal to offset1(AH) through linear interpolation.

[0026] As a preferred technical solution of this application, for offset2(T)

[0027] According to the accuracy requirements, select several temperature points to determine the reference temperature T REF , the temperature point should include T REF ;

[0028] Under the background gas condition, change the ambient temperature to make the temperature reach the temperature point T, and get the voltage V(T). When T=T REF When ADC_0=V(T REF );

[0029] According to V(T) corresponding to the measured temperature point, nonlinear interpolation is performed to obtain the interpolation table lUT_T0(T).

[0030] As a preferred technical solution of the present application, for any helium sensor, its sensitivity factor S and ADC_0

[0031] In the background gas environment, T = T REF , relative humidity is RH, the output signal V(0, T REF );

[0032] When the helium concentration is C He , T≈T REF , the relative humidity is approximately RH, the measured output signal is V(C He , T REF );

[0033] Through T=T REF , relative humidity RH to get absolute humidity AH.

[0034] Beneficial effects: Compared with the prior art, the present invention provides a batch compensation method for a thermal conductivity helium sensor, which has the following beneficial effects: This batch compensation method for a thermal conductivity helium sensor can realize temperature and humidity compensation of the thermal conductivity helium sensor, and only a small amount of testing is required to realize batch calibration, with low test cost and simple process. The entire batch compensation method for the thermal conductivity helium sensor has a simple structure, is easy to operate, and has better effect than the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a batch compensation method for a thermal conductivity helium sensor.

[0036] Figure 2 The present invention is a schematic diagram of a helium sensor circuit model in a batch compensation method for a thermal conductivity helium sensor. DETAILED DESCRIPTION

[0037] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] like Figure 1 , 2 As shown, a batch compensation method for a thermal conductivity helium sensor includes the following steps:

[0041] S1: Select one of the sensors as the standard sensor, set TREF, and measure its LUT_C, LUT_AH and LUT_T;

[0042] S2: Obtain S and ADC_0 of all sensors through ventilation test;

[0043] S3: Write the sensor's S and ADC_0 data into the corresponding sensor;

[0044] S4: Bulk compensation of sensors can be achieved with a small number of experiments.

[0045] It can realize temperature and humidity compensation of thermal conductivity helium sensor. Only a small amount of test is needed to realize batch calibration, with low test cost and simple process.

[0046] Furthermore, for the thermopile, the change in the temperature difference between the hot and cold ends can be approximately considered to be proportional to the change in the thermal conductivity of the gas environment, and the average thermal conductivity of the gas environment is:

[0047] λ x =λ He C He +λ H2O C H2O +λ N2 C N2

[0048] where λ He , H2O , N2 is the thermal conductivity of helium, water vapor, and nitrogen, C HE , C N2 , C H2O The concentrations of helium, nitrogen and water vapor are calculated. Since the water vapor concentration needs to take the atmospheric pressure into consideration and most of the time it is at standard atmospheric pressure, it will be replaced by the absolute humidity associated with it.

[0049] Furthermore, since the thermopile sensitivity coefficient is related to temperature, its temperature coefficient is TC, then: f1(C He , T) = f1(C He , T REF )×(1+TC×(TT REF ))

[0050] Where T REF is the reference temperature, which is determined by the tester. H2O , T), since the thermopile temperature coefficient TC is small, to simplify the steps, it can be considered that the effect of humidity on the thermopile output is independent of temperature.

[0051] Furthermore, a helium sensor is selected as a standard sensor and f1(C He , T REF ), offset1, offset2 methods.

[0052] Furthermore, for f1(C He , T REF ), if the sensor range is 0~FS, then:

[0053] In the background dry gas, the ambient temperature is T REF Under the condition of REF );

[0054] The dry helium concentration is The ambient temperature is T REF Under the condition of

[0055] When the dry helium concentration is FS and the ambient temperature is T REF Under the condition of REF );

[0056] According to f1(0, T REF ), f1(FS,T REF ) to perform nonlinear interpolation and obtain the interpolation table LUT_C (C He ), and then through linear interpolation, LUT_C(C He ) is approximately equal to f1(C He , T REF ).

[0057] Furthermore, for offset1(AH)

[0058] According to the accuracy requirements, select several absolute humidity points and perform nonlinear interpolation to obtain the interpolation table LUT_AH0 (AH). Assume that the absolute humidity points selected are AH0, AH1, and AH2.

[0059] Water vapor is introduced into the background gas, and the required absolute humidity AH is obtained according to the temperature T and relative humidity RH;

[0060] For LUT_AH(C H2O ) can be approximately equal to offset1(AH) through linear interpolation.

[0061] Furthermore, for offset2(T)

[0062] According to the accuracy requirements, select several temperature points to determine the reference temperature T REF , the temperature point should include T REF ;

[0063] Under the background gas condition, change the ambient temperature to make the temperature reach the temperature point T, and get the voltage V(T). When T=T REF When ADC_0=V(T REF );

[0064] According to V(T) corresponding to the measured temperature point, nonlinear interpolation is performed to obtain the interpolation table LUT_T0(T).

[0065] Furthermore, for any helium sensor, its sensitivity factor S and ADC_0

[0066] In the background gas environment, T = T REF , relative humidity is RH, the output signal V(0, T REF );

[0067] When the helium concentration is C He , T≈T REF , the relative humidity is approximately RH, the measured output signal is V(C He , T REF );

[0068] Through T=T REF , relative humidity RH to get absolute humidity AH.

[0069] Figure 2 is the equivalent circuit model, Figure 2 The output voltage V0 is as follows:

[0070] V O =f1(C HE ,T)+offset(AH,T)

[0071] Where f1(C HE , T) is the function of the relationship between the output signal and the helium concentration,

[0072] offset(AH,T) is the offset function of absolute humidity and temperature to the output signal.

[0073] Since the thermopile sensitivity coefficient is related to temperature, its temperature coefficient is TC, then:

[0074] f1(C He , T) = f1(C He , T REF )×(1+TC×(TT REF ))

[0075] Where T REF is the reference temperature, which is determined by the tester. H2O , T), since the thermopile temperature coefficient TC is small, to simplify the steps, it can be considered that the effect of humidity on the thermopile output is independent of temperature.

[0076] So we have:

[0077] offset(AH,T)=offset1(C H2O )+offset2(T)+ADC_0

[0078] offset1(C H2O ) is the absolute humidity offset to the output, ADC_0 is the background gas, and the ambient temperature is T REFThe output voltage under the background gas is related to the sensor itself. offset2(T) is the temperature relative to T under the background gas. REF The output offset caused by the offset, where offset2(T REF )=0

[0079] The offset is mainly due to the fact that the thermopile background gas sensitivity is affected by temperature.

[0080] but:

[0081] V O =f1(C He , T REF )×(1+TC×(TT REF ))+offset1(AH)+offset2(T)+ADC_0

[0082] By getting f1(C He , T REF ), offset1(λH), offset2(T), and ADC_0 to get the actual concentration.

[0083] The main difference between mass-produced sensors is in sensitivity, which can be calibrated in batches through a correction factor. Let the factor be S. S is related to the sensor itself. It mainly affects the sensitivity of the sensor to helium and water vapor concentrations and the relative offset of temperature, and is proportional. For any helium sensor, its signal output V is:

[0084] V=S×{f1(C He , T REF )×(1+TC×(TT REF ))+offset1(AH)+offset2(T)}+ADC_0

[0085] In summary, for a helium sensor, if the output signal is V1, the measured helium concentration is:

[0086]

[0087] It should be noted that, in this article, relational terms such as first and second (number one, number two), etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0088] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A batch compensation method for a thermal conductivity helium sensor, characterized in that: The steps include: S1: Select one of the sensors as the standard sensor, set TREF, and measure its LUT_C, LUT_AH and LUT_T; S2: Obtain S and ADC_0 of all sensors through ventilation test; S3: Write the sensor's S and ADC_0 data into the corresponding sensor; S4: Bulk compensation of sensors can be achieved with a small number of experiments.

2. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: For thermopiles, the change in the temperature difference between the hot and cold ends can be approximately considered to be proportional to the change in the thermal conductivity of the gas environment, and the average thermal conductivity of the gas environment is: l x =λ He C He +λ H2O C H2O +λ N2 C N2 where λ He , H2O , N2 is the thermal conductivity of helium, water vapor, and nitrogen, C HE , C N2 , C H2O The concentrations of helium, nitrogen and water vapor are calculated. Since the water vapor concentration needs to take the atmospheric pressure into consideration and most of the time it is at standard atmospheric pressure, it will be replaced by the absolute humidity associated with it.

3. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: Since the thermopile sensitivity coefficient is related to temperature, its temperature coefficient is TC, then: f1(C He , T) = f1(C He , T REF )×(1+TC×(TT REF )) Where T REF is the reference temperature, which is determined by the tester. H2O , T), since the thermopile temperature coefficient TC is small, to simplify the steps, it can be considered that the effect of humidity on the thermopile output is independent of temperature.

4. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: Select one helium sensor as the standard sensor and design f1(C He , T REF ), offset 1, offset 2 method.

5. The batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: For f1(C He , T REF ), if the sensor range is 0~FS, then: In the background dry gas, the ambient temperature is T REF Under the condition of REF ); The dry helium concentration is The ambient temperature is T REF Under the condition of When the dry helium concentration is FS and the ambient temperature is T REF Under the condition of REF ); According to f1(0, T REF ), f1(FS,T REF ) to perform nonlinear interpolation and obtain the interpolation table LUT_C (C He ), and then through linear interpolation, LUT_C(C He ) is approximately equal to f1(C He , T REF ).

6. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: For offset 1 (AH) According to the accuracy requirements, select several absolute humidity points and perform nonlinear interpolation to obtain the interpolation table LUT_AHO (AH). Assume that the absolute humidity points selected are AH0, AH1, and AH2. Water vapor is introduced into the background gas, and the required absolute humidity AH is obtained according to the temperature T and relative humidity RH; For LUT_AH(C H2O ) can be approximately equal to offset 1 (AH) through linear interpolation.

7. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: For offset 2(T) According to the accuracy requirements, select several temperature points to determine the reference temperature T REF , the temperature point should include T REF ; Under the background gas condition, change the ambient temperature to make the temperature reach the temperature point T, and get the voltage V(T). When T=T REF When ADC_0=V(T REF ); According to V(T) corresponding to the measured temperature point, nonlinear interpolation is performed to obtain the interpolation table LUT_T0(T).

8. A batch compensation method for a thermal conductivity helium sensor according to claim 1, characterized in that: For any helium sensor, its sensitivity factor S and ADC_0 are in the background gas environment, T = T REF , relative humidity is RH, the output signal V(0, T REF ); When the helium concentration is C He , T≈T REF , the relative humidity is approximately RH, the measured output signal is V(C He , T REF ); Through T=T REF , relative humidity RH to get absolute humidity AH.

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