A three-wire heating resistance temperature step measurement method, system, device and medium

Abstract

The application discloses a three-wire heating resistance temperature step measurement method, system, device and medium, and belongs to the technical field of industrial control, and comprises the following steps: acquiring a reference resistance voltage quantity; acquiring a first voltage quantity between a first measurement end of a heating resistance and a common end; acquiring a second voltage quantity between a second measurement end of the heating resistance and the common end; determining a wire voltage quantity between the heating resistance and a sampling circuit based on the first voltage quantity and the second voltage quantity; determining a resistance value of the heating resistance based on the wire voltage quantity, the first voltage quantity and the reference resistance voltage quantity; and cyclically executing the steps of acquiring the first voltage quantity between the first measurement end of the heating resistance and the common end and updating the resistance value of the heating resistance based on the wire voltage quantity, the first voltage quantity and the reference resistance voltage quantity. The three-wire heating resistance temperature step measurement method, system, device and medium improve the sampling response speed and solve the problem that multiple measurements during traditional sampling cause deviation of an input step signal.

Description

Technical Field

[0001] This invention belongs to the field of industrial control technology, specifically relating to a method, system, device, and medium for measuring the temperature step of a three-wire resistance thermometer. Background Technology

[0002] Resistance temperature detectors (RTDs) are widely used in industrial control systems due to their high sensitivity, stability, wide measurement range, and high reliability. RTD temperature signals are typically used to measure the metal temperature of motors in large equipment, providing over-temperature protection for motor components, which is crucial for system safety. Besides requiring high accuracy and stability at the temperature limit, the rate of temperature change is also critical for over-temperature protection. When the temperature signal undergoes a step change, the calculated instantaneous temperature rate is too high, which should be considered an abnormal situation in the protection system. This temperature should be cut off to prevent equipment malfunction. Therefore, accurately measuring the temperature step signal is essential.

[0003] In industrial applications, when acquiring temperature signals, a three-wire resistance thermometer connection is generally used to reduce the influence of ambient temperature on the measurement results. Existing three-wire resistance thermometers measure the voltage between different leads multiple times, and the error caused by line resistance is eliminated by calculating the difference between the leads. (See attached diagram) Figure 1 As shown, however, each calculation of the resistance value of the thermal resistor requires three samplings, resulting in a slow data refresh rate. If an abnormal temperature change occurs between two samplings of the first and second sets of leads, the resistance value R between the first and second sets of leads will deviate significantly, leading to distorted sampling results and making it impossible to measure the step temperature signal normally. Therefore, it is necessary to develop a new three-wire thermal resistor temperature step measurement method, system, device, and medium to solve the existing problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method, system, device, and medium for measuring the temperature step change of a three-wire resistance thermometer, so as to solve the problem that the instantaneous temperature rate obtained is too large when the temperature signal undergoes a step change.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for measuring the temperature step of a three-wire heating resistance thermometer, comprising the following steps:

[0006] Based on the existing three-wire heating resistor wiring method, the reference resistor is sampled and the data is stored first. After the algorithm runs in a loop, the reference resistor is no longer measured, which can improve the sampling response speed. Based on the existing three-wire heating resistor wiring method, the resistance between different leads is measured separately, the resistance of the long lead is calculated and temporarily stored.

[0007] After the algorithm starts cyclic sampling, it only needs to sample the two ends of the external thermal resistor once, which solves the problem of deviation in the input step signal caused by multiple measurements in traditional sampling.

[0008] When the external thermal resistor is broken or malfunctions, the mechanism of sampling and calculating the long wire resistance of only one channel in each cycle avoids slowing down the response time due to the simultaneous calculation of the long wire resistance of multiple channels in one cycle.

[0009] Preferably, based on the traditional wiring method of a three-wire heating resistor, the expression for sampling the reference resistor is as follows:

[0010] U ref =I*R ref ;

[0011] Where: I represents the excitation current, R ref This indicates the resistance value of the reference resistor.

[0012] Preferably, the two sets of leads of the three-wire heating resistor are In1+ and In1-, and In2+ and In2-, respectively; the expressions for sampling the two sets of leads U1 and U2 are:

[0013] U1 = I*(R+r);

[0014] U2 = I*(R+2r);

[0015] The sampled value of the resistance of the long conductor can be calculated based on U1 and U2:

[0016] U r =U2-U1=I*(R+2r)-I*(R+r)=I*r;

[0017] Where: r represents the resistance of the conductor. In a three-wire system, the three conductors can be considered to be of equal length, and the resistance of the three conductors is r.

[0018] The three-wire heating resistor has three wires as measurement terminals. The wires connected to the In1+ / In2+ pins are considered the common terminal. There is resistance between the common terminal and the other two measurement terminals. The other two measurement terminals are the first measurement terminal and the second measurement terminal, and the first measurement terminal and the second measurement terminal are shorted.

[0019] Preferably, after the algorithm starts cyclic sampling, it only needs to measure the voltage between one set of leads (In1+ and In1-) of the three-wire heating resistor. The expression for the accurate calculation of the heating resistor R is:

[0020] R = U / I = (U1 - U) r ) / I;

[0021] I = U ref / R ref ;

[0022] R = U / U ref *R ref =(U1-U r ) / U ref *R ref ;

[0023] The expression for the traditional algorithm is:

[0024] R = U / I = 2*(U1-U2) / I;

[0025] R = U / U ref *R ref =2*(U1-U2) / U ref *R ref ;

[0026] The calculation results show that, using the traditional three-wire resistance temperature detector (RTD) measurement method, to accurately calculate the RTD signal, the algorithm needs to sample U in each loop. ref The original algorithm required three sets of data (In1, U1, and U2) to calculate the result; however, with the improved algorithm, each cycle only needs to sample the voltage U1 between one set of leads (In1+ and In1-) of the three-wire heating resistor to accurately calculate the heating resistor signal.

[0027] The present invention also provides a three-wire resistance temperature step measurement system, the system comprising:

[0028] The reference resistor acquisition module is used to acquire the voltage of the reference resistor.

[0029] The first voltage acquisition module is used to acquire the first voltage between the first measuring terminal and the common terminal of the resistance temperature detector.

[0030] The second voltage acquisition module is used to acquire the second voltage between the second measuring terminal and the common terminal of the thermal resistor;

[0031] A conductor voltage determination module is used to determine the conductor voltage between the thermal resistor and the sampling circuit based on a first voltage value and a second voltage value.

[0032] The resistance value determination module is used to determine the resistance value of the resistance temperature detector based on the wire voltage, the first voltage, and the reference resistor voltage.

[0033] The resistance value update module of the thermal resistor is used to cyclically execute the step of obtaining the first voltage between the first measuring terminal and the common terminal of the thermal resistor, and update the resistance value of the thermal resistor based on the wire voltage, the first voltage and the voltage of the reference resistor.

[0034] The present invention also provides a three-wire heating resistance temperature step measurement device, comprising:

[0035] Memory for storing non-transitory computer-readable instructions; and

[0036] A processor is configured to execute the computer-readable instructions such that, when the computer-readable instructions are executed by the processor, the three-wire resistance temperature step measurement method is implemented.

[0037] The present invention also provides a computer-readable storage medium for storing non-transitory computer-readable instructions, which, when executed by a computer, cause the computer to perform the three-wire resistance temperature step measurement method.

[0038] The technical effects and advantages of this invention are as follows: Based on existing three-wire resistance thermometer wiring methods, this method, system, device, and medium for measuring temperature step changes in a three-wire resistance thermometer first samples and stores the data of a reference resistor. After the algorithm runs in a loop, it no longer measures the reference resistor, thus improving the sampling response speed. It calculates the wire resistance by measuring the resistance between different leads and stores the data. During the algorithm's loop, it only measures the voltage between the leads at both ends of the external resistance thermometer, solving the problem of deviations in the input step signal caused by multiple measurements in traditional sampling. When the external resistance thermometer experiences a broken wire or abnormality, the multi-channel wire resistance is measured in turn, avoiding slow response time caused by simultaneous calculation of wire resistance across multiple channels.

[0039] This application first measures the reference resistance before sampling the RTD signal, and calculates the wire resistance using the principle of three-wire measurement. Only one sampling operation is needed to accurately calculate the RTD resistance value. When the three-wire RTD signal is disconnected, a polling method is used to recalculate the wire resistance, avoiding the reduction in refresh rate caused by simultaneous calculation of multiple wire resistances in one cycle. This solves the problem of abnormal measurement results caused by temperature step changes in traditional three-wire RTD measurement and improves the measurement refresh rate. It can better reflect the actual rate of temperature change and provides over-temperature protection for bearings and motors in large equipment. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the sampling principle of the multi-channel three-wire heating resistor of the present invention;

[0041] Figure 2 This is a schematic diagram of the multi-channel three-wire heating resistor sampling algorithm of the present invention;

[0042] Figure 3 The graph shows the response of the three-wire heating resistor to a step signal during temperature measurement according to the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The existing three-wire heating resistor measures the voltage between different wires multiple times and eliminates the error caused by the wire resistance by calculating the difference between the different wires.

[0045] Sampling of the reference resistor: U ref =I*R ref ;

[0046] Sampling of the resistance between the first set of leads In1+ and In1-: U1 = I*(R+r);

[0047] The resistance between the second set of leads In2+ and In2- is sampled: U2 = I*(R+2r);

[0048] The resistance of the three-wire heating resistor can be calculated as: R = U / U ref *R ref =2*(U1-U2) / U ref *R ref To accurately calculate the RTD signal using the above method, the algorithm needs to sample U in each loop. ref The result can only be calculated from three sets of data: U1 and U2. Furthermore, the measurement results are abnormal due to temperature step changes during measurement, and the measurement refresh rate is relatively slow.

[0049] To solve the above problems, such as Figure 2 As shown, this application provides a method for measuring the temperature step of a three-wire resistance thermometer, comprising the following steps:

[0050] Step 1, in order to obtain the value of the reference resistor (voltage U) ref As a reference for comparison, the resistance value of the measured resistor is calculated proportionally to the size of the reference resistor.

[0051] Based on the traditional wiring method of three-wire heating resistors, before the algorithm starts its loop, the external reference resistor is sampled and the data is stored:

[0052] U ref =I*R ref ;

[0053] Because the reference resistance is fixed and does not change with the external thermal resistance, it only needs to be measured once and the data stored. This data can be called up during sampling calculations.

[0054] Step 2, see appendix Figure 1 The resistance (voltage U1) between measuring terminal 1 and the common terminal, and the resistance (voltage U2) between measuring terminal 2 and the common terminal are measured separately. Subtracting the two values ​​yields the resistance (voltage U) of the wire between the measured resistor and the sampling circuit. r );

[0055] In the prior art, R = (2*U1-U2) / U ref* R ref The resistance value of the resistor being measured is calculated. This method is used for each sampling. When measuring a step signal, a jump occurs.

[0056] Based on the sampling results of the first two steps, this application can calculate the resistance (voltage) U of the conductor. r = (U2-U1), the resistance of the wire is a fixed value for a given measured thermal resistance;

[0057] After the algorithm runs in a loop, it samples the voltage corresponding to the resistance between In1+ and In1- of the two sets of leads of the three-wire heating resistor, and the voltage corresponding to the resistance between In2+ and In2-, calculates the sampled value of the resistance of the long conductor, and temporarily stores it.

[0058] U1 = I*(R+r);

[0059] U2 = I*(R+2r);

[0060] The sampled value of the resistance of the long conductor can be calculated based on U1 and U2:

[0061] U r =U2-U1=I*(R+2r)-I*(R+r)=I*r;

[0062] After the external RTD is connected to the sampling system, the resistance of the long conductor becomes a fixed value. The calculated data can also be temporarily stored as an intermediate quantity for calculating the RTD.

[0063] Steps 1 and 2 yield two definite values ​​U. ref and U r After that, each subsequent sampling loop only requires completing step 3;

[0064] Step 3: Obtain the resistance (voltage U1) between measuring terminal 1 and common terminal.

[0065] The method for calculating the resistance being measured is as follows:

[0066] (U1-U r ) / U ref* R ref (R ref (Typically 100 ohms); Step 3 specifically includes:

[0067] After the algorithm starts running in a loop, the voltage between the leads (In1+ and In1-) of one of the external thermal resistors is used again:

[0068] U1 = I*(R+r);

[0069] The voltage between the leads (In1+ and In1-) of the external thermal resistor includes the voltage corresponding to both the thermal resistor and the wire resistance. The wire resistance of the long wire has already been calculated before the algorithm starts looping. Therefore, by subtracting the voltage corresponding to the long wire resistance from the voltage between the leads (In1+ and In1-) of the external thermal resistor, the external thermal resistor can be accurately calculated.

[0070] U = U1 - U r =I*(R+r)-I*r=I*R;

[0071] I = U / R = U ref / R ref ;

[0072] R = U / U ref *R ref =(U1-U r ) / U ref *R ref ;

[0073] After sampling begins and continuous refreshing, the reference resistance U used for calculation... ref and long conductor resistance U r The sampling and storage are completed before the algorithm loop. During the algorithm loop, only a single measurement of the voltage between the leads (In1+ and In1-) at both ends of the external RTD is needed to accurately calculate the external RTD. Using this algorithm, the sampling response speed of the RTD signal is greatly improved, and the defect of measurement anomalies caused by sudden temperature changes is effectively solved.

[0074] Step 4: To ensure measurement accuracy, the wire resistance should be remeasured at intervals, preferably every 5 minutes; Figure 2 As shown, during the first measurement, the process follows the arrows downwards until the external thermal resistance is calculated. At this time, the conductor voltage is also calculated and stored. Next, the calculation enters a loop. Within 5 minutes, the conductor voltage does not need to be calculated again. After 5 minutes, the set time is up, and the method recalculates the conductor voltage.

[0075] If the wire resistance of multiple RTDs is measured simultaneously in the same cycle, it will result in a significant increase in the cycle period, affecting other functions. Therefore, the wire resistance of only one RTD should be measured in the same cycle.

[0076] For example: when the time reaches the 5th minute, calculate the voltage across the wires of the first thermal resistor;

[0077] When the time reaches 10 minutes, calculate the voltage across the wires of the second thermal resistor;

[0078] At the 15-minute mark, calculate the voltage across the wires of the third thermal resistor...

[0079] At the 40-minute mark, calculate the voltage across the wires of the 8th thermal resistor...

[0080] Then the time is reset to zero, and the voltage across the first RTD is calculated again at the 5-minute mark. The voltage calculation interval for each RTD is 5 minutes. This method is used when there are multiple RTDs to ensure that the time for each cycle is as even as possible, reducing disturbances.

[0081] The cycle period refers to the time it takes for all the measured thermal resistors to complete one round of measurement; the calculation method is sampling frequency * number of measured thermal resistors. In the implementation of the method of this application, the cycle period is 150ms * 8 = 1.2 seconds.

[0082] When a break in the wire occurs after replacing the external RTD, the resistance of the long lead may change, requiring remeasurement and recalculation. To avoid slowing down the response time due to multiple channels calculating the long lead resistance within a single cycle, the long lead resistance of only one channel is sampled and calculated in each cycle. That is, the long lead resistance of the first channel is measured and calculated in the first cycle, the long lead resistance of the second channel is measured and calculated in the second cycle, and so on, until the long lead resistance of all channels has been measured and calculated.

[0083]

[0084] Where #channel is the channel number and interval is the interval time. Different channels correspond to different cycle periods. The resistance of long wires can be measured and calculated in different cycle periods according to the channel number order.

[0085] Appendix Figure 3 The image shows the response curve to a step signal when using the algorithm proposed in this invention for temperature measurement of a three-wire heating resistor. It can be seen that based on this scheme, when a step occurs in the external heating resistor, it can correctly reflect the stage change of temperature, and will not exhibit abnormal data abrupt changes when sampling step signals in traditional three-wire heating resistors.

[0086] The present invention also provides a three-wire resistance temperature step measurement system, the system comprising:

[0087] The reference resistor acquisition module is used to acquire the voltage of the reference resistor.

[0088] The first voltage acquisition module is used to acquire the first voltage between the first measuring terminal and the common terminal of the resistance temperature detector.

[0089] The second voltage acquisition module is used to acquire the second voltage between the second measuring terminal and the common terminal of the thermal resistor;

[0090] A conductor voltage determination module is used to determine the conductor voltage between the thermal resistor and the sampling circuit based on a first voltage value and a second voltage value.

[0091] The resistance value determination module is used to determine the resistance value of the resistance temperature detector based on the wire voltage, the first voltage, and the reference resistor voltage.

[0092] The resistance value update module of the thermal resistor is used to cyclically execute the step of obtaining the first voltage between the first measuring terminal and the common terminal of the thermal resistor, and update the resistance value of the thermal resistor based on the wire voltage, the first voltage and the voltage of the reference resistor.

[0093] The present invention also provides a three-wire heating resistance temperature step measurement device, comprising:

[0094] Memory for storing non-transitory computer-readable instructions; and

[0095] A processor is configured to execute the computer-readable instructions such that, when the computer-readable instructions are executed by the processor, the three-wire resistance temperature step measurement method is implemented.

[0096] The present invention also provides a computer-readable storage medium for storing non-transitory computer-readable instructions, which, when executed by a computer, cause the computer to perform the three-wire resistance temperature step measurement method.

[0097] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0098] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0099] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0100] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0101] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0102] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0103] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the temperature step of a three-wire heating resistance thermometer, characterized in that: include: Before the algorithm starts running in a loop, the voltage of the reference resistor is acquired and stored; Obtain the first voltage between the first measuring terminal and the common terminal of the resistance temperature detector (RTD). Obtain the second voltage between the second measuring terminal and the common terminal of the resistance temperature detector; The voltage across the wire from the thermal resistor to the sampling circuit is determined and stored based on the first voltage value and the second voltage value. After sampling begins and refreshes continuously, the algorithm only measures the first voltage between the first measuring terminal and the common terminal during the loop, and determines the resistance value of the thermal resistor based on the wire voltage, the first voltage, and the reference resistor voltage. The process iteratively executes the step of obtaining the first voltage between the first measuring terminal and the common terminal of the thermal resistor, and updates the resistance value of the thermal resistor based on the wire voltage, the first voltage, and the reference resistor voltage.

2. The method for measuring the temperature step of a three-wire heating resistance as described in claim 1, characterized in that: The method further includes: performing the steps of periodically acquiring a first voltage between the first measuring terminal of the thermal resistor and the common terminal and acquiring a second voltage between the second measuring terminal of the thermal resistor and the common terminal, and updating the wire voltage value.

3. The method for measuring the temperature step of a three-wire heating resistance as described in claim 1, characterized in that: The determination of the conductor voltage between the thermal resistor and the sampling circuit based on the first voltage value and the second voltage value includes: calculating the conductor voltage value based on the first voltage value and the second voltage value. U r =U2-U1; Among them: U r U1 represents the first voltage quantity, and U2 represents the second voltage quantity.

4. The method for measuring the temperature step of a three-wire heating resistance as described in claim 1, characterized in that: The method for determining the resistance value of the thermal resistor based on the conductor voltage, the first voltage, and the reference resistor voltage includes: a method for calculating the resistance value of the thermal resistor. R=U / I=(U1-U r ) / I; I=U ref / R ref ; R=U / U ref *R ref =(U1-U r ) / U ref *R ref ; Where R represents the resistance of the thermal resistor, U r U1 represents the first voltage, I represents the excitation current, and R represents the conductor voltage. ref U represents the resistance value of the reference resistor. ref This indicates the voltage across the reference resistor.

5. The method for measuring the temperature step of a three-wire heating resistance as described in claim 1, characterized in that: The method further includes: When there are multiple thermal resistors, multiple thermal resistors are measured in turn.

6. The method for measuring the temperature step of a three-wire heating resistance according to claim 2, characterized in that: The interval for performing the steps of acquiring the first voltage between the first measuring terminal and the common terminal of the thermal resistor and acquiring the second voltage between the second measuring terminal and the common terminal is 5 minutes.

7. The method for measuring the temperature step of a three-wire heating resistance as described in claim 5, characterized in that: When measuring multiple resistance thermometers in turn, the measurement interval between two resistance thermometers is 5 minutes.

8. A three-wire resistance temperature step measurement system, the system comprising: The reference resistor acquisition module is used to acquire and store the reference resistor voltage before the algorithm starts its loop. The first voltage acquisition module is used to acquire the first voltage between the first measuring terminal and the common terminal of the resistance temperature detector. The second voltage acquisition module is used to acquire the second voltage between the second measuring terminal and the common terminal of the thermal resistor; A conductor voltage determination module is used to determine and store the conductor voltage between the thermal resistor and the sampling circuit based on a first voltage and a second voltage. The RTD resistance value determination module is used to measure only the first voltage between the first measuring terminal and the common terminal during the algorithm loop after continuous refreshing starts sampling, and to determine the RTD resistance value based on the wire voltage, the first voltage and the reference resistor voltage. The resistance value update module of the thermal resistor is used to cyclically execute the step of obtaining the first voltage between the first measuring terminal and the common terminal of the thermal resistor, and update the resistance value of the thermal resistor based on the wire voltage, the first voltage and the voltage of the reference resistor.

9. A three-wire resistance temperature step measurement device, comprising: Memory is used to store non-transitory computer-readable instructions; as well as A processor for executing the computer-readable instructions such that, when executed by the processor, the computer-readable instructions implement the three-wire resistance temperature step measurement method according to any one of claims 1 to 7.

10. A computer-readable storage medium for storing non-transitory computer-readable instructions that, when executed by a computer, cause the computer to perform the three-wire resistance temperature step measurement method according to any one of claims 1 to 7.

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