Channel self-calibration method, system and application

Abstract

The invention belongs to the technical field of equipment calibration, and discloses a channel self-calibration method and system and application, and the method comprises the steps: collecting an original measurement value of a measurement device, calculating a zero offset value based on the original measurement value, and obtaining a zero offset calibration result; collecting a standard calibration signal of the measuring device, and calculating a bipolar gain coefficient based on the standard calibration signal to obtain a bipolar gain calibration result; and respectively verifying the zero offset calibration result and the bipolar gain calibration result, and generating a calibration report according to the verified calibration results. According to the invention, through a bipolar separation calibration parameter system, a dynamic correction factor is introduced for the asymmetric error characteristic of a negative signal, so that the negative measurement error is reduced, and the precision of a positive signal is synchronously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of equipment calibration, and in particular to a channel self-calibration method, system and application. Background Art

[0002] A high-precision measuring device refers to an instrument that can provide extremely accurate and stable measurement results. It is usually used to accurately measure physical quantities (such as temperature, pressure, current, voltage, etc.). High-precision measuring devices may have measurement deviations due to factors such as usage time, environmental changes, and component aging. Calibration can detect whether the instrument is still working according to the expected standards, thereby ensuring the accuracy of its measurement results.

[0003] The calibration of measuring devices in the prior art mostly relies on regular manual calibration with external standard sources, which not only increases the cost of equipment maintenance, but also may lead to inaccurate or untimely calibration due to complex operations. As time and environmental conditions change (such as temperature, humidity, etc.), sensor performance will drift, resulting in increased deviation in measurement results. However, the prior art usually lacks efficient automatic calibration functions and requires manual intervention to complete the calibration process, which is inefficient and prone to errors.

[0004] Existing technologies often focus on hardware-level improvements, while ignoring the role of software algorithms in optimizing the calibration process. Existing voltage measurement equipment is prone to reduced measurement accuracy after long-term use due to environmental changes, component aging, and other factors. The traditional calibration process requires return to the factory or reliance on professional tools, which is inefficient and costly. In addition, the calibration of positive and negative polarity signals in the existing technology is not processed separately, resulting in the accumulation of negative signal measurement errors and insufficient stability.

[0005] Therefore, how to provide a channel self-calibration method, system and application is a problem that needs to be solved urgently. Summary of the invention

[0006] The embodiments of the present invention provide a channel self-calibration method, system and application to solve the problem in the prior art that the positive and negative polarity signal calibration is not processed separately, resulting in the accumulation of negative signal measurement errors and insufficient stability.

[0007] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended to be a general review, nor is it intended to identify key / important components or to delineate the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0008] According to a first aspect of an embodiment of the present invention, a channel self-calibration method is provided.

[0009] In one embodiment, the channel self-calibration method includes:

[0010] Collecting original measurement values ​​of the measuring device, calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result;

[0011] Collecting a standard calibration signal of a measuring device, calculating a bipolar gain coefficient based on the standard calibration signal, and obtaining a bipolar gain calibration result;

[0012] The zero offset calibration result and the bipolar gain calibration result are verified respectively, and a calibration report is generated according to the verified calibration results.

[0013] In one embodiment, collecting the original measurement value of the measuring device, calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result includes:

[0014] Switch the internal relay matrix of the measuring device, short-circuit the target channel to the ground terminal, continuously collect the original measurement values, remove the abnormal values ​​of the original measurement values ​​and take the average value to obtain the original measurement average value;

[0015] A ground reference value is obtained based on a self-checking circuit of the measuring device, and a zero point offset value is calculated by combining a predefined correction factor, the ground reference value and an original measurement mean value, and the zero point offset value is stored in a non-volatile memory.

[0016] In one embodiment, the calculation formula of the zero offset value is:

[0017] Offset=Raw-Ground-Adjustment;

[0018] In the formula, Offset represents the zero offset value; Raw represents the original measurement value; Ground represents the ground reference value; and Adjustment represents the correction factor.

[0019] In one embodiment, the collecting the standard calibration signal of the measuring device, calculating the bipolar gain coefficient based on the standard calibration signal, and obtaining the bipolar gain calibration result includes:

[0020] Outputting a standard calibration signal based on a built-in voltage source of the measuring device, wherein the standard calibration signal includes a positive polarity standard voltage signal and a negative polarity standard voltage signal;

[0021] Combine the positive polarity standard voltage signal with the zero offset value to calculate the positive polarity gain coefficient;

[0022] The negative polarity standard voltage signal is combined with a predefined correction factor to calculate a negative polarity gain coefficient;

[0023] The positive polarity gain coefficients and the negative polarity gain coefficients are stored in a calibration file.

[0024] In one embodiment, the calculation formula of the positive polarity gain coefficient is:

[0025] Pos Gain=Reference / (Raw-Offset);

[0026] The calculation formula of the negative polarity gain coefficient is:

[0027] Neg Gain=Reference / (Raw-Offset)*Adjustment;

[0028] In the formula, Pos Gain represents the positive polarity gain coefficient; Neg Gain represents the negative polarity gain coefficient; Reference represents the reference value; Adjustment represents the correction factor; Raw represents the original measurement value; and Ground represents the ground reference value.

[0029] In one embodiment, the initial value of the correction factor is 1.0; the adjustment range of the correction factor is 0.9995 to 1.0005; and the adjustment step of the correction factor is less than or equal to 0.0001.

[0030] According to a second aspect of an embodiment of the present invention, a channel self-calibration system is provided.

[0031] In one embodiment, the channel self-calibration system comprises:

[0032] A zero offset calibration module is used to collect the original measurement value of the measuring device, calculate the zero offset value based on the original measurement value, and obtain the zero offset calibration result;

[0033] A gain calibration module, used for collecting a standard calibration signal of a measuring device, calculating a bipolar gain coefficient based on the standard calibration signal, and obtaining a bipolar gain calibration result;

[0034] The calibration result verification module is used to verify the zero offset calibration result and the bipolar gain calibration result respectively, and generate a calibration report according to the verified calibration results.

[0035] According to a third aspect of an embodiment of the present invention, there is provided an application of a channel self-calibration method in a dual-mode measurement device.

[0036] In one embodiment, the dual-mode measurement device comprises:

[0037] Channel differential input module, used to synchronize the measurement of thermocouple and voltage signals;

[0038] A self-calibration submodule is used to divide the channel into a number of calibration modules using a multi-channel calibration mechanism, and a relay switching matrix is ​​configured in each group of calibration modules;

[0039] Dynamic compensation module, which monitors temperature and load changes in real time and uses a closed-loop feedback algorithm to achieve voltage bias stability;

[0040] Test verification interface, used to connect an external standard voltmeter for post-calibration verification and generate a calibration report that meets preset standards.

[0041] In one embodiment, the output range covers ±10mV, ±67mV, ±100mV, ±1V and ±10V.

[0042] In one embodiment, the dynamic compensation module integrates a cold-end temperature compensation circuit, and automatically switches to an equivalent voltage measurement mode when the thermocouple is open circuit;

[0043] Wherein, the cold end temperature compensation circuit includes a signal input module and a signal processing module;

[0044] The signal input module is used to achieve cold-end compensation through the thermistor, correct the error caused by the temperature change of the reference end of the thermocouple, and provide a bias signal in combination with the voltage divider circuit composed of the resistor R1 and the resistor R2;

[0045] The signal processing module is used to select different input channels through a multiplexer, amplify the signal selected by the multiplexer through a programmable gain amplifier, and then input it into an analog-to-digital converter for analog-to-digital conversion.

[0046] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0047] 1. The channel self-calibration method provided by the present invention solves the problems of high calibration complexity, poor long-term stability, low degree of automation and insufficient hardware and software integration in the prior art. It is particularly suitable for domestically produced high-precision measuring devices, such as 48-channel precision thermocouples and voltage acquisition instruments. The present invention can significantly improve the accuracy and reliability of the measuring device and meet the needs of modern industry and scientific research for high-precision data acquisition.

[0048] 2. The present invention can monitor and automatically adjust the status of each channel in real time without affecting normal work, ensure the long-term stability and accuracy of data acquisition, and enhance the degree of automation. The present invention adopts a combination of advanced algorithms and hardware design to achieve fully automatic calibration without manual participation, thereby improving work efficiency and reliability. In addition, through in-depth research on the best combination of hardware and software, a complete self-calibration solution has been developed, which includes both hardware design and software algorithm optimization to achieve the best calibration effect.

[0049] 3. The present invention adopts a bipolar separation calibration parameter system (positive / negative polarity coefficients are stored independently) to introduce a dynamic correction factor for the asymmetric error characteristics of negative signals, thereby reducing the negative polarity measurement error and improving the accuracy of positive signals simultaneously. The multi-range high-precision voltage source adopts a segmented voltage divider network and low temperature coefficient resistors, and cooperates with the full range coverage of the self-calibration process to ensure that the error is better than 2.5 in any range.

[0050] 4. In the present invention, the user triggers the self-calibration mode through a web page or the instrument's LAN expansion interface, and the full-range calibration can be completed within 30 minutes without returning to the factory or relying on external standard instruments. The calibration efficiency is improved by more than 80% compared with traditional manual calibration. Through the sequential control of zero point calibration and gain calibration (zero point first, then gain) and the automatic parameter storage function, the risk of misoperation caused by manual intervention is avoided, and the standardization of the calibration process is improved.

[0051] 5. The present invention reduces the influence of temperature drift on the calibration result through forced preheating and temperature adaptive logic, ensuring long-term stable operation of the equipment within a wide temperature range of 40°C to 85°C. The calibration parameters are stored in a non-volatile memory, and the calibration parameter loss rate after power failure is less than 0.1%, avoiding the parameter failure problem caused by frequent erasing and writing of traditional Flash storage.

[0052] 6. The present invention enables users to complete calibration independently, saving the logistics, labor costs and equipment downtime losses of returning to the factory for calibration, reducing the cost of a single calibration by about 90%, and through the parameter backtracking function (storing the most recent calibration records), quickly locate the cause of accuracy degradation, reduce troubleshooting time and spare parts replacement frequency.

[0053] 7. The present invention can complete calibration through a web interface, reducing dependence on professional technicians. It is particularly suitable for remote areas or rapid detection scenarios. The external verification interface supports closed-loop verification, which enhances user confidence in the calibration results and reduces the risk of disputes caused by measurement errors, thereby reducing the packaging materials, transportation energy consumption and electronic waste required for factory calibration, which is in line with the trend of green manufacturing and low-carbon economy.

[0054] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0056] Figure 1 is a flow chart of a channel self-calibration method according to an exemplary embodiment;

[0057] Figure 2is a principle block diagram of a dual-mode measurement device according to an exemplary embodiment;

[0058] Figure 3 is a principle block diagram of a channel self-calibration method according to an exemplary embodiment;

[0059] Figure 4 is a cold-end temperature compensation circuit diagram in a dual-mode measurement device according to an exemplary embodiment;

[0060] Figure 5 is a thermocouple measurement principle diagram in a dual-mode measurement device according to an exemplary embodiment;

[0061] Figure 6 It is a principle block diagram of a channel self-calibration system according to an exemplary embodiment. DETAILED DESCRIPTION

[0062] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0063] The terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. in this document indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this document and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of this document, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can also be the internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0064] As used herein, the term "plurality" means two or more than two, unless otherwise specified.

[0065] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0066] In this article, the term "and / or" is a description of the association relationship between objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or, A and B.

[0067] It should be understood that, although the various steps in the flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the figure may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0068] Each module in the device or system of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above modules.

[0069] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0070] Figure 1An embodiment of the channel self-calibration method of the present invention is shown.

[0071] In this optional embodiment, the channel self-calibration method includes:

[0072] Step S101, collecting original measurement values ​​of the measuring device, calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result;

[0073] Step S102, collecting a standard calibration signal of the measuring device, calculating a bipolar gain coefficient based on the standard calibration signal, and obtaining a bipolar gain calibration result;

[0074] Step S103: verifying the zero offset calibration result and the bipolar gain calibration result respectively, and generating a calibration report according to the verified calibration results.

[0075] In this optional embodiment, the collecting the original measurement value of the measuring device (the measuring device is a thermocouple and voltage dual-mode measuring device), calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result includes:

[0076] Switch the internal relay matrix of the measuring device, short-circuit the target channel to the ground terminal, continuously collect original measurement values, eliminate abnormal values ​​of the original measurement values ​​and take the average to obtain the original measurement average; obtain the ground reference value based on the self-test circuit of the measuring device, calculate the zero point offset value in combination with the predefined correction factor, the ground reference value and the original measurement average, and store the zero point offset value in the non-volatile memory.

[0077] In this optional embodiment, the collecting the standard calibration signal of the measuring device, calculating the bipolar gain coefficient based on the standard calibration signal, and obtaining the bipolar gain calibration result includes:

[0078] Based on the built-in voltage source of the measuring device, a standard calibration signal is output, and the standard calibration signal includes a positive polarity standard voltage signal and a negative polarity standard voltage signal; the positive polarity standard voltage signal is combined with a zero point offset value to calculate a positive polarity gain coefficient; the negative polarity standard voltage signal is combined with a predefined correction factor to calculate a negative polarity gain coefficient; the positive polarity gain coefficient and the negative polarity gain coefficient are stored in a calibration file.

[0079] In this optional embodiment, the initial value of the correction factor is 1.0; the adjustment range of the correction factor is 0.9995 to 1.0005; and the adjustment step of the correction factor is less than or equal to 0.0001.

[0080] Figure 6 An embodiment of the channel self-calibration system of the present invention is shown.

[0081] In this optional embodiment, the channel self-calibration system includes:

[0082] The zero offset calibration module 301 is used to collect the original measurement values ​​of the measuring device, calculate the zero offset value based on the original measurement values, and obtain the zero offset calibration result;

[0083] The gain calibration module 302 is used to collect a standard calibration signal of the measuring device, calculate a bipolar gain coefficient based on the standard calibration signal, and obtain a bipolar gain calibration result;

[0084] The calibration result verification module 303 is used to verify the zero offset calibration result and the bipolar gain calibration result respectively, and generate a calibration report according to the verified calibration results.

[0085] like Figure 3 As shown, the channel self-calibration method of the present invention is further described below in conjunction with specific embodiments:

[0086] Step 1: Design of multi-range high-precision voltage source and test interface:

[0087] The device has a built-in high-precision voltage source that supports multiple ranges from ±10mV to ±10V, and the output value has 6 significant digits. There is a test interface on the back for connecting an external standard voltmeter for post-calibration verification.

[0088] The present invention provides a multi-range standard signal source to cover the full-range calibration requirements of the equipment and reduce the dependence on external calibration equipment; the test interface realizes closed-loop verification to ensure the reliability of the calibration result, and adopts a combination of a segmented voltage divider network and a low temperature coefficient resistor, combined with a high-stability operational amplifier, to ensure that the output accuracy of the voltage source is better than ±0.005% within a wide range.

[0089] Step 2: Zero offset calibration and bipolar gain calibration:

[0090] Among them, the zero offset calibration includes controlling the internal short circuit of the target channel, collecting the original measurement value and calculating the zero offset value, and storing it in the non-volatile memory;

[0091] Bipolar gain calibration includes outputting a positive polarity standard voltage signal and calculating a positive polarity gain coefficient based on a zero offset value; outputting a negative polarity standard voltage signal and calculating a negative polarity gain coefficient in combination with a correction factor;

[0092] The initial value of the correction factor is 1.0, the adjustment range is limited to 0.9990-1.0010, and the adjustment step is ≤0.0001; the calibration report includes the range, polarity, error before and after calibration, and correction factor records.

[0093] The present invention realizes 48-channel efficient calibration (<15 minutes) through the independently designed multi-channel group calibration mechanism and dynamic compensation algorithm, and gets rid of the dependence on imported calibration equipment; and has a bipolar independent correction mechanism, by separating the positive / negative polarity gain calibration path, combined with closed-loop verification to automatically optimize the correction factor, to ensure that the full range accuracy is better than ±0.025%; integrated abnormal channel automatic locking, one-key generation of calibration report and historical data tracing functions, reduce maintenance costs by more than 60%, specifically:

[0094] The measuring device of the present invention realizes rapid calibration without external tools through an embedded self-calibration system, including:

[0095] Preparation before calibration:

[0096] Environmental requirements: Equipment preheating ≥ 60 minutes, internal temperature fluctuation < ±0.5℃ (monitored by built-in temperature sensor); external signal input is cut off during calibration; Operation trigger: control the start of calibration and view calibration files through the web interface; support LXI protocol remote command startup (compliant with IEEE 1588 standard).

[0097] Zero offset calibration:

[0098] Channel short circuit: Switch the internal relay matrix to short the target channel to the ground terminal;

[0099] Data collection: collect 10 original measurement values ​​continuously, and take the average value after removing abnormal values;

[0100] Bias calculation:

[0101] The reference parameter (FacOffset) is read from the memory;

[0102] Calculate the zero offset value: Offset = original measurement mean - ground reference value - correction factor;

[0103] The ground reference value (Ground) is obtained in real time through the equipment self-test circuit;

[0104] Parameter storage: Offset values ​​are stored independently in non-volatile memory according to the range;

[0105] Key rules:

[0106] The default value of the correction factor (Adjustment) is 0, which is enabled only when there is an out-of-tolerance in the historical calibration;

[0107] The calibration range covers the entire range (±10mV to ±10V);

[0108] Positive polarity gain calibration:

[0109] Standard signal output: built-in voltage source outputs positive polarity standard value (such as +10mV);

[0110] Data calculation:

[0111] Calculate the corrected voltage value based on the Offset value of the current range;

[0112] Update the positive polarity gain coefficient (FacNegCoff):

[0113] FacPosCoff = standard value / (measured value - Offset);

[0114] Parameter write: Store the updated FacNegCoff.

[0115] Negative Gain Calibration:

[0116] Standard signal output: switch to negative polarity standard value (such as 10mV);

[0117] Data calculation:

[0118] Combined with the correction factor to compensate for the nonlinear error, the negative polarity gain coefficient (FacNegCoff) is updated:

[0119] FacNegCoff = standard value / |measured value-Offset|×Adjustment;

[0120] Store the updated FacNegCoff.

[0121] Correction factor rules: Initial value: 1.0 Adjustment range: 0.9995~1.0005 (step 0.0001) Trigger condition: Forced adjustment when the calibration error is greater than ±0.02% for three consecutive times.

[0122] It should be noted that:

[0123] Raw represents the original sampling value, that is, the unprocessed digital value obtained from the ADC;

[0124] Ground represents the ground reference value, that is, the ideal value when the input is shorted to ground (usually 0);

[0125] Adjustment represents the correction factor, i.e., the correction value used to compensate for the asymmetry of the system;

[0126] Offset represents the zero point offset, that is, the calculated channel inherent deviation value;

[0127] The calculation formula of the positive polarity gain coefficient is:

[0128] Pos Gain=Reference / (Raw-Offset);

[0129] Where: Pos Gain represents the positive gain coefficient, that is, the proportional factor used to calibrate the positive polarity signal; Reference represents the reference value, that is, the standard value provided by the high-precision voltage source; Raw represents the original sampling value, that is, the measured unprocessed digital value; Offset represents the zero point offset, that is, the calculated channel deviation value;

[0130] Negative polarity signals introduce a correction factor Adjustment, and the calculation formula for the negative polarity gain coefficient is:

[0131] Neg Gain=Reference / (Raw-Offset)*Adjustment;

[0132] Where: Neg Gain represents the negative gain coefficient, that is, the proportional factor used to calibrate the negative polarity signal; Reference represents the reference value, that is, the standard value provided by the high-precision voltage source; Raw represents the original sampling value, that is, the measured unprocessed digital value; Offset represents the zero point offset, that is, the calculated channel deviation value; Adjustment represents the correction factor, that is, to compensate for the nonlinear error in the negative measurement.

[0133] Post-calibration verification:

[0134] Accuracy index (actual test data), range ± self-calibration mode error ± uncalibrated mode error:

[0135] ±10.0V±(0.025%+500μV)±(0.05%+1mV);

[0136] ±1.0V±(0.025%+50μV)±(0.05%+100μV);

[0137] ±0.1V±(0.025%+10μV)±(0.05%+20μV);

[0138] ±0.067V±(0.025%+10μV)±(0.05%+20μV);

[0139] ±0.01V±(0.050%+10μV)±(0.10%+20μV);

[0140] Verification method:

[0141] Connect a standard voltmeter (such as Keysight 3458A) through the rear test interface and generate a calibration report (including error comparison, correction records and environmental parameters);

[0142] For example, using the ±10mV range calibration:

[0143] Zero calibration:

[0144] The measured original mean value is 0.0015mV;

[0145] Ground reference value: 0.0001mV;

[0146] Calculate Offset: 0.0015-0.0001=0.0014mV;

[0147] Positive Gain Calibration:

[0148] Output +10.0000mV, measured 10.0020mV;

[0149] Calculate FacPosCoff: 10.0000 / (10.00200.0014)=0.9998;

[0150] Negative Gain Calibration:

[0151] Output 10.0000mV, measured 10.0050mV;

[0152] Calculate FacNegCoff: 10.0000 / (10.00500.0014)×1.0000=0.9994;

[0153] Step 3: Self-calibration mode and control logic:

[0154] The device enters self-calibration mode through the web interface or LXI (LANe Xtensions for Instrumentation) remote command and executes the following process:

[0155] Preheating and environmental stabilization: Forced preheating ≥ 60 minutes, temperature sensor feedback data until the fluctuation is < ± 0.5℃.

[0156] Zero point calibration priority: All measurement channels are short-circuited internally to ensure that subsequent gain calibration is based on the zero point correction result.

[0157] Range traversal calibration: Switch the range in the order of ±10mV→±10V, and complete the positive and negative polarity calibration one by one.

[0158] Reduce the impact of temperature drift through forced preheating; avoid error transmission through strict calibration sequence; ensure consistency through full range coverage; realize remote calibration trigger through LXI interface, combined with temperature adaptive control logic, improve the adaptability of calibration environment.

[0159] Step 4: Non-volatile storage and parameter backtracking:

[0160] Calibration parameters (Offset, PosGain, NegGain) are stored in EMMC, supporting power-off saving and historical data backtracking. Users can view the most recent calibration record through the interface, compare parameter change trends, and save calibration data for a long time to facilitate fault diagnosis and accuracy degradation analysis.

[0161] Based on the above, the connection relationship between the steps can be summarized as follows:

[0162] Step 1 to Step 2:

[0163] The multi-range high-precision voltage source provides standard calibration signals ranging from ±10mV to ±10V. These signals are switched to the measurement channel through the internal CALBUS relay and serve as the input source for the bipolar separation calibration in step 2. The test interface is used for external verification to ensure the accuracy of the calibration parameters calculated in step 2.

[0164] Step 2 to Step 3:

[0165] The bipolar separation calibration parameters (Fac10osCoff, FacNegCoff) serve as the core algorithm basis of the self-calibration mode; the calculation results of the zero offset and gain calibration will be verified in the calibration process of step three; the correction factor Adjustment is dynamically adjusted in the range traversal calibration of step three.

[0166] Step 3 to Step 4: After the self-calibration mode is executed, the calibration parameters (Offset, PosGain, NegGain) are generated and passed to Step 4 for non-volatile storage. The temperature sensor data is also recorded for parameter traceback analysis.

[0167] Step 4 to Step 1:

[0168] The stored historical calibration data can be used to evaluate the long-term stability of the voltage source; parameter change trend analysis helps determine whether recalibration is needed and provides a reference benchmark for the next round of calibration.

[0169] Figure 2 An embodiment of the application of the channel self-calibration method of the present invention in a dual-mode measurement device is shown.

[0170] In this optional embodiment, the dual-mode measurement device includes:

[0171] A channel differential input module 201 is used to measure the thermocouple and voltage signals synchronously;

[0172] The self-calibration submodule 202 is used to divide the channel into a plurality of calibration modules by using a multi-channel calibration mechanism, and a relay switching matrix is ​​configured in each group of calibration modules;

[0173] Dynamic compensation module 203, used to monitor temperature and load changes in real time and achieve voltage bias stability using a closed-loop feedback algorithm;

[0174] The test verification interface 204 is used to connect an external standard voltmeter to perform post-calibration verification and generate a calibration report that meets preset standards.

[0175] In this optional embodiment, the self-calibration submodule has a built-in voltage source, and the output range covers ±10mV, ±67mV, ±100mV, ±1V and ±10V.

[0176] In this optional embodiment, the dynamic compensation module integrates a cold-end temperature compensation circuit and automatically switches to an equivalent voltage measurement mode when the thermocouple is open.

[0177] Wherein, the cold end temperature compensation circuit includes a signal input module and a signal processing module;

[0178] The signal input module is used to achieve cold-end compensation through the thermistor, correct the error caused by the temperature change of the reference end of the thermocouple, and provide a bias signal in combination with the voltage divider circuit composed of the resistor R1 and the resistor R2;

[0179] The signal processing module is used to select different input channels through a multiplexer, amplify the signal selected by the multiplexer through a programmable gain amplifier, and then input it into an analog-to-digital converter for analog-to-digital conversion.

[0180] The dual-mode measurement device of the present invention is further described below in conjunction with specific embodiments:

[0181] The measuring device in the present invention is a thermocouple and voltage dual-mode measuring device, which comprises:

[0182] 48-channel differential input module: supports synchronous measurement of thermocouples (J / K / T / E / S / R / B / N type) and voltage signals, input impedance ≥40MΩ, common mode input range ±10V, with overvoltage protection;

[0183] Self-calibration submodule: built-in high-precision voltage source, output range covers ±10mV, ±67mV,

[0184] ±100mV, ±1V, ±10V, with non-volatile memory to store zero offset value, positive / negative polarity gain coefficient and correction factor;

[0185] Dynamic compensation module: real-time monitoring of temperature and load changes, and achieving voltage bias stability through a closed-loop feedback algorithm;

[0186] The closed-loop feedback algorithm principle includes:

[0187] 1. Cold junction compensation (CJC) principle;

[0188] 2. Use a high-precision thermistor to monitor the cold end temperature;

[0189] 3. One CJC sensor is configured for every 4 thermocouple channels;

[0190] 4. The CJC sensor is installed close to the isothermal plate to reduce temperature gradient error;

[0191] 5. Correct the voltage deviation caused by the cold end temperature through the compensation algorithm;

[0192] 6. Self-calibration closed-loop feedback mechanism;

[0193] 7. Switch to the internal calibration source via the CALBUS relay;

[0194] 8. Provide multiple precision reference voltages such as ±9.4592V and ±0.9598V;

[0195] 9. Real-time monitoring of signal path gain and bias drift;

[0196] 10. Dynamically compensate for system errors caused by temperature changes;

[0197] The specific implementation process includes:

[0198] Step 1: Initialization phase:

[0199] The system was preheated for 60 minutes to reach thermal equilibrium;

[0200] Load factory calibration data into non-volatile memory;

[0201] Initialize the CJC sensor and signal conditioning circuit;

[0202] Configure ADC sampling parameters and digital filters;

[0203] Step 2: Self-calibration process:

[0204] Disconnect the input signal relay;

[0205] Switch to CALBUS calibration mode;

[0206] Inject the reference voltage in sequence;

[0207] -±9.4592V (full scale calibration);

[0208] -±0.9598V (mid-range calibration);

[0209] -±0.09564V (small signal calibration);

[0210] Collect calibration data and calculate correction factors;

[0211] storing the calibration results in volatile memory;

[0212] Step 3: Dynamic compensation mechanism:

[0213] Real-time monitoring of CJC temperature changes; calculation of temperature coefficient: supports J, K, T, E, S, R, B, N type thermocouples, in accordance with IEC / NIST standard polynomial fitting; application of correction algorithm to correct measurement results.

[0214] Test Verification Port: Located on the back of the device, it supports connecting an external standard voltmeter and generates a calibration report that complies with the ISO 17025 standard.

[0215] The self-calibration submodule adopts a multi-channel calibration mechanism, dividing the 48 channels into 6 groups of independent calibration units, each group is equipped with an independent relay switching matrix, and the calibration time is ≤15 minutes;

[0216] The dynamic compensation module integrates a cold junction temperature compensation circuit (CJC accuracy ±0.1°C), and automatically switches to an equivalent voltage measurement mode when the thermocouple is open circuit;

[0217] The cold end temperature compensation circuit diagram is as follows Figure 4 As shown, Figure 4 The main components include:

[0218] Thermocouple: used as temperature sensor;

[0219] Thermistor: used for cold-end compensation;

[0220] Operational amplifier (PGA): Programmable gain amplifier;

[0221] ADC: analog-to-digital converter;

[0222] Multiplexer (Mux): used for signal switching;

[0223] Multiple resistors and capacitors: used for signal conditioning;

[0224] The working principle of the cold junction temperature compensation circuit diagram includes:

[0225] Signal input part: Thermocouples generate weak thermoelectric potential signals; the thermistor is used for cold-end compensation to compensate for the error caused by the temperature change of the reference end of the thermocouple; resistors R1 and R2 form a voltage divider circuit to provide bias for the thermistor.

[0226] Signal processing part: The multiplexer (Mux) can select different input channels (AIN1-AIN4); the signal is amplified by the PGA to increase the amplitude of the weak signal; the amplified signal is sent to the ADC for analog-to-digital conversion.

[0227] Reference voltage section: The internal reference voltage (Internal Reference) provides a stable reference;

[0228] REFCOM, REFP, and REFN are used to set the reference voltage range of the ADC.

[0229] The test verification interface supports LXI protocol communication, and automatically triggers abnormal channel positioning when the calibration error is greater than ±0.01%.

[0230] In addition, if Figure 5 As shown, the core elements of temperature adaptive control include:

[0231] Cold Junction Compensation (CJC) Design:

[0232] 1. Physical structure;

[0233] 2.Isothermal Block design;

[0234] 3. Every 4 channels are equipped with 1 precision thermistor;

[0235] 4. The metal partition separates the front-end measurement area and the rear-end power supply area;

[0236] 5. Large thermal mass design slows down temperature fluctuations;

[0237] Measurement timing:

[0238] 1. CJC sensor and input channel synchronous sampling (time difference <1ms);

[0239] 2. Real-time monitoring of 12 thermistor temperature data;

[0240] 3. Dynamically compensate for the impact of ambient temperature changes;

[0241] Temperature stability control:

[0242] 1. Preheating control;

[0243] 2. Mandatory 60-minute warm-up time;

[0244] 3. Monitor the temperature change rate until it stabilizes (fluctuation < ±0.5°C);

[0245] 4. The warm-up limit can be overridden by repeating the calibration command;

[0246] 5. Validity judgment: Ambient temperature changes exceeding ±5°C trigger a recalibration recommendation; Thermocouple temperature calculation logic includes:

[0247] 1. Collection of thermocouple original voltage;

[0248] 2. Cold end temperature measurement;

[0249] 3. Calculation of cold junction compensation voltage;

[0250] 4. Calculate the total voltage and perform gain correction;

[0251] 5. Nonlinear conversion to obtain temperature value;

[0252] Among them, the actual temperature is calculated as:

[0253] T actual =f(V measured +V cjc );

[0254] Where, T actual Indicates the actual temperature; V measured Represents the measured thermocouple voltage; V cjc represents the cold-end compensation voltage; f() represents the characteristic equation corresponding to the thermocouple type.

[0255] Cold junction compensation voltage calculation:

[0256] V cjc =g(T cjc );

[0257] Where, T cjc represents the cold end temperature; g() represents the inverse characteristic equation.

[0258] It should be noted that the measurement principle of thermocouples includes: The measurement principle is based on the Seebeck effect. When two different metals (such as Ni-Al and Ni-Cr) are connected at different temperatures, a voltage is generated at their junction. This voltage is proportional to the temperature difference. The temperature difference between the measuring end (measuring junction) and the cold end (reference end) of the thermocouple causes a voltage change, thereby measuring the temperature. Figure 5 The K-type thermocouple composed of Ni-Al and Ni-Cr is connected to the measurement environment at the measuring end, while the cold end is connected to the cold end temperature compensation circuit through a copper wire. In order to compensate for the temperature change error of the cold end, a thermistor is used and a voltage divider circuit composed of R1 and R2 is used to provide a bias for the thermistor. The signal processing module selects different input channels (AIN1-AIN4) through a multiplexer (Mux). The signal is amplified by a programmable gain amplifier (PGA) to increase the amplitude of the weak signal. The amplified signal is sent to the analog-to-digital converter (ADC) for analog-to-digital conversion and finally converted into a digital signal output.

[0259] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A channel self-calibration method, characterized in that: The method includes: Collecting original measurement values ​​of the measuring device, calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result; Collecting a standard calibration signal of a measuring device, calculating a bipolar gain coefficient based on the standard calibration signal, and obtaining a bipolar gain calibration result; The zero offset calibration result and the bipolar gain calibration result are verified respectively, and a calibration report is generated according to the verified calibration results.

2. The channel self-calibration method according to claim 1, characterized in that: The collecting the original measurement value of the measuring device, calculating the zero offset value based on the original measurement value, and obtaining the zero offset calibration result includes: Switch the internal relay matrix of the measuring device, short-circuit the target channel to the ground terminal, continuously collect the original measurement values, remove the abnormal values ​​of the original measurement values ​​and take the average value to obtain the original measurement average value; A ground reference value is obtained based on a self-checking circuit of the measuring device, and a zero point offset value is calculated by combining a predefined correction factor, the ground reference value and an original measurement mean value, and the zero point offset value is stored in a non-volatile memory.

3. The channel self-calibration method according to claim 2, characterized in that: The calculation formula of the zero offset value is: Offset=Raw-Ground-Adjustment; In the formula, Offset represents the zero offset value; Raw represents the original measurement value; Ground represents the ground reference value; and Adjustment represents the correction factor.

4. The channel self-calibration method according to claim 1, characterized in that: The collecting the standard calibration signal of the measuring device, calculating the bipolar gain coefficient based on the standard calibration signal, and obtaining the bipolar gain calibration result comprises: Outputting a standard calibration signal based on a built-in voltage source of the measuring device, wherein the standard calibration signal includes a positive polarity standard voltage signal and a negative polarity standard voltage signal; Combine the positive polarity standard voltage signal with the zero offset value to calculate the positive polarity gain coefficient; The negative polarity standard voltage signal is combined with a predefined correction factor to calculate a negative polarity gain coefficient; The positive polarity gain coefficients and the negative polarity gain coefficients are stored in a calibration file.

5. The channel self-calibration method according to claim 4, characterized in that: The calculation formula of the positive polarity gain coefficient is: Pos Gain=Referenc / (Raw-Offset); The calculation formula of the negative polarity gain coefficient is: Neg Gain=Reference / (Raw-Offset)*Adjustment; In the formula, Pos Gain represents the positive polarity gain coefficient; Neg Gain represents the negative polarity gain coefficient; Reference represents the reference value; Adjustment represents the correction factor; Raw represents the original measurement value; and Ground represents the ground reference value.

6. The channel self-calibration method according to claim 4, characterized in that: The initial value of the correction factor is 1.0; the adjustment range of the correction factor is 0.9995 to 1.0005; and the adjustment step of the correction factor is less than or equal to 0.0001.

7. A channel self-calibration system, characterized in that: The system includes: A zero offset calibration module is used to collect the original measurement value of the measuring device, calculate the zero offset value based on the original measurement value, and obtain the zero offset calibration result; A gain calibration module, used for collecting a standard calibration signal of a measuring device, calculating a bipolar gain coefficient based on the standard calibration signal, and obtaining a bipolar gain calibration result; The calibration result verification module is used to verify the zero offset calibration result and the bipolar gain calibration result respectively, and generate a calibration report according to the verified calibration results.

8. Application of a channel self-calibration method in a dual-mode measurement device, characterized in that: The dual-mode measurement device comprises: Channel differential input module, used to synchronize the measurement of thermocouple and voltage signals; A self-calibration submodule is used to divide the channel into a number of calibration modules using a multi-channel calibration mechanism, and a relay switching matrix is ​​configured in each group of calibration modules; Dynamic compensation module, which monitors temperature and load changes in real time and uses a closed-loop feedback algorithm to achieve voltage bias stability; Test verification interface, used to connect an external standard voltmeter for post-calibration verification and generate a calibration report that meets preset standards.

9. Application of the channel self-calibration method according to claim 8 in a dual-mode measurement device, characterized in that: The self-calibration submodule has a built-in voltage source, and the output range covers ±10mV, ±67mV, ±100mV, ±1V and ±10V.

10. Application of the channel self-calibration method according to claim 8 in a dual-mode measurement device, characterized in that: The dynamic compensation module integrates a cold-end temperature compensation circuit and automatically switches to an equivalent voltage measurement mode when the thermocouple is open-circuited; Wherein, the cold end temperature compensation circuit includes a signal input module and a signal processing module; The signal input module is used to achieve cold-end compensation through the thermistor, correct the error caused by the temperature change of the reference end of the thermocouple, and provide a bias signal in combination with the voltage divider circuit composed of the resistor R1 and the resistor R2; The signal processing module is used to select different input channels through a multiplexer, amplify the signal selected by the multiplexer through a programmable gain amplifier, and then input it into an analog-to-digital converter for analog-to-digital conversion.

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