A temperature controlled table with built-in automatic calibration circuit and method from reference source self-calibration

Abstract

The application relates to a temperature control table built-in automatic calibration circuit and method with reference source self-calibration, and belongs to the technical field of circuit calibration. The temperature control table built-in automatic calibration circuit and method with reference source self-calibration comprises a control module, the control module is electrically connected with a sensor signal measurement module, a reference signal production module and a reference source self-checking module; the reference source self-checking module comprises reference sources A and B; the control module judges whether single-source drift occurs in the reference sources according to the two reference sources; an internal reference source C is further arranged in the control module; the reference source self-checking module is used for outputting the reference source C voltage Vc to the control module; when the control module judges that no abnormality occurs in the reference sources according to the two voltages, the control module judges whether abnormality occurs in the reference source A according to the two voltages Va and Vc; when it is judged that abnormality occurs, the reference sources A and B are closed and a double-source drift alarm is sent; the reference source C is a control module internal band gap reference voltage.

Description

Technical Field

[0001] This invention belongs to the field of circuit calibration technology, specifically relating to a built-in automatic calibration circuit and method for a temperature controller with a reference source for calibration. Background Technology

[0002] Temperature controllers are among the most commonly used instruments in industrial production, widely applied in industries such as chemical, metallurgical, food, and pharmaceutical. Their measurement accuracy directly affects product quality and production safety. During circuit operation, the output of electrical signals may drift due to factors such as component aging and environmental changes, leading to a decrease in the measurement accuracy of electronic devices and inaccurate output results.

[0003] The common solution is to set up a calibration circuit. The principle is as follows: using a reference source that does not experience voltage drift or has extremely low voltage drift, the system determines whether the voltage difference between the main sensing circuit output voltage and the reference source voltage differs from the voltage difference measured at the factory, and then calculates the correction value. However, the reference source itself may also deviate due to environmental influences or aging, in which case the correction value itself cannot be trusted. For this reason, a common solution is a parameter self-calibration system disclosed in CN114513208A, which includes a microcontroller, a controllable switch, an adjustable reference source, an adjustable reference source output voltage adjustment circuit, an ADC sampling point, an operational amplifier circuit, a zero-point drift suppression circuit, and a temperature drift suppression circuit. The microcontroller is connected to the adjustable reference source through the adjustable reference source output voltage adjustment circuit. The adjustable reference source and the ADC sampling point are connected to the controllable switch. The controllable switch is used to switch the adjustable reference source calibration circuit and the ADC sampling point working circuit. The controllable switch is connected to the operational amplifier circuit, and the operational amplifier circuit is connected to the zero-point drift suppression circuit, the temperature drift suppression circuit, and the microcontroller's AD sampling port. This invention relates to a control method for a parameter self-calibration system; it improves the data display accuracy of the product through a reference source calibration loop.

[0004] However, the calibration source and its calibration loop may also shift due to various environmental factors. The general solution is to set up two voltage reference chips at the same time, taking advantage of the completely different physical characteristics of the two chips in terms of aging and temperature drift: when one of the reference sources drifts due to aging, the voltage difference between the two reference sources will change accordingly. By periodically cross-detecting and continuously comparing the current difference with the initial difference at the factory, the aging of the reference source itself can be accurately detected and identified. However, the premise upon which the above scheme relies, namely that "the two reference sources will not drift in the same direction at the same time," is not naturally true in engineering practice. Various factors can cause simultaneous offsets, thus rendering this premise invalid and causing errors in the entire verification mechanism. For example, when the overall temperature changes, drifts in the same direction may occur. For instance, at high temperatures, both output voltages may rise slightly. When the dual-voltage chip is offset synchronously, the cross-verification between the two calibration sources cannot achieve the purpose of self-calibration. However, manually verifying the reference sources would consume a lot of manpower. Therefore, a temperature controller with a built-in automatic calibration circuit and method that has an automated self-calibration function and accurate calibration results is needed, which includes a reference source for calibration. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a built-in automatic calibration circuit and method for a temperature controller with a reference source for calibration, which features automatic self-calibration while providing accurate calibration results.

[0006] The objective of this invention can be achieved through the following technical solutions: A temperature controller with a reference source for calibration has a built-in automatic calibration circuit, including a control module. The control module is electrically connected to a sensor signal measurement module, a reference signal production module, and a reference source calibration module. The reference source verification module includes reference source A and reference source B. The reference source verification module is used to output reference source voltages Va and Vb to the control module. The control module determines whether the reference source is abnormal based on the two voltages. When an abnormality is detected, the control module outputs an external reference source signal to shut down the abnormal reference source and issues a single-source drift alarm. The reference source is used to output a reference voltage to the reference signal production module. The sensor signal measurement module is used to connect to the temperature sensor of the temperature controller. The reference signal production module converts the reference voltage into a reference signal and uploads it to the control module, which is used to calculate the calibration value based on the reference signal. The control module is also equipped with an internal reference source C. The reference source verification module is used to output the reference source C voltage Vc to the control module. When the control module determines that the reference source is not abnormal based on the two voltages, it determines whether the reference source A is abnormal based on the two voltages Va and Vc. When it determines that an abnormality has occurred, it shuts down the reference sources A and B and issues a dual-source drift alarm. The reference source C is the internal bandgap reference voltage of the control module.

[0007] As a preferred embodiment of the present invention, it further includes a sensing module, which is electrically connected to the control module. The sensing module is used to collect the internal temperature of the control module, and the control module determines whether the temperature deviates from the standard value and corrects the reference signal when the determination result is yes.

[0008] As a preferred embodiment of the present invention, the control module adds a correction coefficient A1 to the reference signal, where A1 = k1 × (T / T0) + c1, and k1 and c1 are pre-input constants, and T0 is a pre-input temperature standard value.

[0009] As a preferred embodiment of the present invention, the sensing module is further used to measure the power supply voltage of the control module and upload it to the control module. The control module determines whether the power supply voltage deviates from the standard value, and further corrects the reference signal when the determination result is yes.

[0010] As a preferred embodiment of the present invention, the control module adds a correction coefficient A2 to the reference signal, where A2 = k2 × (V / V0) + c2, and k2 and c2 are pre-input constants, and V0 is a pre-input nominal power supply voltage.

[0011] As a preferred embodiment of the present invention, it further includes a human-computer interaction module, which is electrically connected to the control module and is used to display single-source drift alarm and dual-source drift alarm.

[0012] This invention also provides a calibration method for a temperature controller with a built-in automatic calibration circuit for reference source calibration, applicable to the aforementioned temperature controller with a built-in automatic calibration circuit for reference source calibration, comprising the following steps: Step 1: Set up reference source A, reference source B and reference source C, set the automatic calibration conditions and start the temperature measurement circuit; Step 2: When the automatic calibration conditions are met, start the calibration and compare reference source A and reference source B. If the comparison result shows an abnormal difference between the two, proceed to step 3; otherwise, proceed to step 4. Step 3: Determine which of the reference sources, A and B, is abnormal. After the determination is complete, turn off the abnormal reference source and proceed to Step 5. Step 4: The control module determines whether dual-source drift has occurred by judging whether the voltage of reference source A is abnormal based on reference source C. If the judgment result is yes, reference sources A and B are turned off and step 6 is executed. If the judgment result is no, step 5 is executed. Step 5: The control module calculates the calibration value based on the still-running reference source and stores the calculated calibration value in non-volatile memory; Step Six: Output one of the following three results: normal, single-source drift alarm, or common-mode drift, and continue to run the temperature measurement circuit. Calibrate the electrical signal of the temperature measurement circuit according to the calibration value in the non-volatile memory.

[0013] The beneficial effects of this invention are as follows: (1) By setting reference sources A, B and C, in each automatic calibration, before calculating the calibration value of the main circuit of the temperature controller, the reference sources are used in the calibration process. When the two external reference sources A and B are mutually verified without error, it may mean that no offset or synchronous offset has occurred. The built-in reference source is verified with reference source A to determine whether synchronous offset has occurred. This avoids the situation where the two reference sources cannot be detected when they are synchronously offset. It also uses the high-precision external reference source to complete the calibration of the main circuit, ensuring the accuracy of the calibration results. (2) By setting temperature detection, the reference signal is linearly corrected when the temperature deviates from the standard value, and environmental and working condition compensation is performed for the subtle effects caused by ambient temperature, which further improves the accuracy of calibration results; (3) By setting the power supply voltage detection, the reference signal is linearly corrected when the power supply voltage deviates from the standard value, and environmental and operating condition compensation is performed for the subtle influence caused by ambient temperature, which further improves the accuracy of the calibration results. Attached Figure Description

[0014] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the overall automatic calibration steps of the present invention; Figure 2 This is a schematic diagram of the automatic calibration steps of the reference source in this invention; Figure 3 This is a block diagram of the control loop of the present invention. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0017] Please see Figure 1-3 A temperature controller with a reference source for calibration has a built-in automatic calibration circuit. The automatic calibration circuit includes a control module, a sensor signal measurement module, a reference signal production module, a reference source verification module, a signal processing link, a human-machine interaction module, and a non-volatile storage module. The control module uses an STM32F103RCT6 MCU, which integrates a bandgap reference source. This internal bandgap reference source is calibrated at the factory, and its output voltage varies by no more than ±1% over the entire temperature range. This internal bandgap reference source is used as the reference source C in this invention. The sensor signal measurement module is used to receive the electrical signal output by the temperature sensor of the temperature controller, and its output terminal is connected to the input terminal of the signal processing link. The reference signal production module receives a reference voltage from reference source A or reference source B, and converts the reference voltage into multiple reference signals corresponding to different temperature points through a voltage divider network composed of precision resistors. Each reference signal is connected to the input terminal of the signal processing link. The sensor signal measurement module and the reference signal production module are respectively connected to different input terminals of the first electronic switch. The first electronic switch is controlled by the control module, which selects to connect the sensor signal measurement module and the reference signal production module to the signal processing link by controlling the first electronic switch. The reference source verification module includes reference source A, reference source B, and a second electronic switch controlled by the control module. Reference source A uses a bandgap reference chip ADR431, and reference source B uses a buried Zener reference chip REF5050. Both have an initial accuracy of ±0.05% and a temperature drift of less than 5ppm / ℃. The outputs of both are connected to different inputs of the second electronic switch. The second electronic switch is controlled by the control module, and its output is connected to the input of the signal processing link. The control module selects whether to connect the output voltage of reference source A or reference source B to the signal processing link by controlling the second electronic switch. The signal processing link includes a signal conditioning module and an ADC analog-to-digital conversion module, which perform the same processing on all input signals. The output is connected to the control module, and the input is used to receive signals from the sensor signal measurement module, the reference signal production module, and the reference source calibration module. In the reference source verification module, reference source A and reference source B are used to output their respective output voltages Va and Vb to the control module. The control module is pre-input with the factory voltages Va0 and Vb0 of reference sources A and B. The control module determines whether the two reference sources have drifted by comparing the difference between |Va-Vb| and |Va0-Vb0|. If the difference between |Va-Vb| and |Va0-Vb0| exceeds the first threshold, it indicates that single-source drift has occurred. Then, it is determined whether |Va-Va0| is greater than |Vb-Vb0|. If |Va-Va0| < |Vb-Vb0|, it means that the deviation between Vb and the reference source B is too large, and the reference source B is unusable. Otherwise, it means that the reference source A is unusable. After the judgment, the unusable reference source is marked as unusable, the unusable reference source is turned off, a reference source aging warning is issued through the human-computer interaction module, and the reference source drift event is recorded in the calibration log to complete one automatic reference source calibration. Since reference source A and reference source B use different technical principles, their aging characteristics and temperature drift characteristics are different. Under normal use conditions, they will not experience aging drift in the same direction and amplitude. At this time, the two reference sources can confirm that no offset has occurred or locate the reference source that has drifted by performing the above-mentioned automatic calibration process. However, when the ambient temperature changes significantly or both are subjected to the same external stress, the output voltages of both may still change in the same direction. In this case, the abnormality cannot be detected by simply comparing the difference between Va and Vb. To this end, the control module also acquires the output voltage Vc of the internal bandgap reference source through its internal analog-to-digital conversion channel and compares Vc with Va. This internal bandgap reference source is the reference source C. After each automatic calibration process is started, the control module first performs automatic calibration of the reference source. Specifically, the second electronic switch is controlled to connect the output voltages of reference source A and reference source B to the signal processing link in sequence. After being conditioned by the signal processing link, the voltages are converted into digital quantities by the ADC and sent to the control module. The control module determines whether the two reference sources have drifted by comparing the difference between |Va-Vb| and |Va0-Vb0|. If the difference between |Va-Vb| and |Va0-Vb0| exceeds the first threshold, it indicates that single-source drift has occurred. If the difference between |Va-Vb| and |Va0-Vb0| is less than the first threshold, there are two possibilities: either neither has drifted, or both have experienced common-mode drift with the same direction and amplitude. To distinguish between these two situations, the control module further compares whether the difference between |Va-Vc| and |Va0-Vc0| exceeds the second threshold. Since the reference source C is the internal bandgap reference of the control module, it is in a different physical environment and stress field from the external reference sources A and B. The probability of all three drifting with the same direction and amplitude at the same time is extremely low. Therefore, if the difference between |Va-Vc| and |Va0-Vc0| exceeds the second threshold, it is determined that reference source A and reference source B have experienced common-mode drift. The control module shuts down reference source A and reference source B and outputs a dual-source drift alarm. The automatic calibration of the reference source is completed. Subsequently, if no dual-source drift occurs, the control module performs automatic calibration. That is, the control module controls the first electronic switch to switch to the available reference signal source between reference signal source A and reference signal source B to output a signal to the reference signal production module. The ADC collects the digital values ​​corresponding to all reference signals output by the reference signal production module and calculates the calibration value. Finally, the control module controls the first electronic switch to switch back to the sensor signal measurement module, which is used to connect the electrical signal output by the temperature sensor of the temperature controller.

[0018] At this point, the three-reference cross-validation is completed. When the two external reference sources do not drift relative to each other, the built-in reference source C is introduced for common-mode verification, which can effectively detect the abnormal situation of synchronous drift of the two external reference sources. When the two external reference sources drift relative to each other, the built-in reference source C is used as a third-party reference, which can accurately identify the specific reference source that has drifted. By setting reference sources A, B, and C, during each automatic calibration, before calculating the calibration value of the temperature controller's main circuit, the built-in reference source is checked against reference source A in the calibration process. If the two external reference sources A and B are mutually verified without error, which may indicate that no offset or synchronous offset has occurred, the internal reference source is checked against reference source A to determine whether synchronous offset has occurred. This avoids the situation where synchronous offset between the two reference sources cannot be detected. It also utilizes the high-precision external reference source to complete the calibration of the main circuit, ensuring the accuracy of the calibration results.

[0019] Since the signal conditioning module and ADC analog-to-digital conversion module in the signal processing link may experience parameter drift with changes in ambient temperature, if the calibration value is calculated using an uncompensated reference signal, the calibration result will include the temperature drift error of the signal processing link, thus affecting the final temperature measurement accuracy. Therefore, in this embodiment, the control module is electrically connected to a sensing module, which includes a temperature sensor. The temperature sensor is located inside the control module or near the signal processing link and is used to collect the ambient temperature T inside the control module and upload it to the control module. In the automatic calibration process, after the control module obtains the current ambient temperature T collected by the sensor module, the control module determines whether the temperature deviates from the standard value, and corrects the reference signal when the determination result is yes. Specifically, the control module adds a correction coefficient A1 to the reference signal, where A1 = k1 × (T / T0) + c1, and k1 and c1 are pre-input constants, and T0 is a pre-input temperature standard value; The values ​​of k1 and c1 are obtained by measuring and calibrating the gain variation characteristics of the signal processing link under different ambient temperatures at the time of manufacture. The control module adds a temperature correction coefficient A1 to each reference signal value output by the reference signal production module to obtain a temperature-compensated reference signal value, and then uses this compensated reference signal value as a reference to calculate the current calibration value. By setting temperature detection, the reference signal is linearly corrected when the temperature deviates from the standard value, and environmental and operating condition compensation is performed to address the subtle effects of ambient temperature, further improving the accuracy of the calibration results.

[0020] Similarly, since the gain of the signal processing link is also affected by fluctuations in the supply voltage, when the supply voltage deviates from the nominal value, the amplification factor of the signal conditioning module and the reference voltage of the ADC analog-to-digital conversion module will change, causing the overall gain of the signal processing link to deviate. If this deviation is not compensated, the acquired reference signal value will not be able to truly reflect the actual gain state of the signal processing link, thus affecting the accuracy of the calibration value. To this end, the sensing module also includes a voltage detection circuit. The input of the voltage detection circuit is connected to the power supply of the control module. It is used to collect the current power supply voltage V of the control module in real time and upload it to the control module. The control module determines whether the power supply voltage deviates from the standard value and further corrects the reference signal when the determination result is yes. Specifically, the control module adds a correction coefficient A2 to the reference signal, where A2 = k2 × (V / V0) + c2, where k2 and c2 are pre-input constants, and V0 is the pre-input nominal power supply voltage. At this time, the reference signal is the value of A1 and A2 added, and the current calibration value is calculated with reference to the reference signal value after double compensation. By setting a power supply voltage detection, the reference signal is linearly corrected when the power supply voltage deviates from the standard value. Environmental and operating condition compensation is performed to address the subtle effects caused by ambient temperature, further improving the accuracy of the calibration results. The human-machine interface module is electrically connected to the control module. The human-machine interface module includes a display panel and operation buttons. The display panel is used to display the current measured temperature, calibration status, single-source drift alarm and dual-source drift alarm information. The operation buttons are used for users to manually trigger the calibration process or configure automatic calibration parameters. The non-volatile memory module uses a ferroelectric memory FM24CL16, which is electrically connected to the control module. It is used to store factory reference data, historical calibration values, reference source drift records, calibration logs, and temperature compensation coefficients k1 and c1 and power supply compensation coefficients k2 and c2. The factory reference data includes Va0, Vb0 and Vc0, the standard values ​​of each reference signal point, the standard temperature value T0 and the nominal power supply voltage V0; It also has automatic calibration trigger conditions. The control module monitors the system status in real time and automatically starts the calibration program when any of the following preset conditions are met: the temperature controller timer's cumulative running time reaches the preset value; the temperature controller's internal ambient temperature changes beyond the preset threshold; the temperature controller's power supply voltage fluctuates beyond the preset range; the deviation between the temperature controller's continuous multiple measurements and the historical average value stored in the non-volatile memory module exceeds the preset value; or the temperature controller's power-on self-test detects that the measurement error exceeds the allowable range.

[0021] This invention also provides a calibration method for a temperature controller with a built-in automatic calibration circuit for reference source calibration, applicable to the aforementioned temperature controller with a built-in automatic calibration circuit for reference source calibration, comprising the following steps: Step 1: Set up reference source A, reference source B and reference source C, set the automatic calibration conditions and start the temperature measurement circuit; Step 2: When the automatic calibration conditions are met, start the calibration and compare reference source A and reference source B. If the comparison result shows an abnormal difference between the two, proceed to step 3; otherwise, proceed to step 4. Step 3: Determine which of the reference sources, A and B, is abnormal. After the determination is complete, turn off the abnormal reference source and proceed to Step 5. Step 4: The control module determines whether dual-source drift has occurred by judging whether the voltage of reference source A is abnormal based on reference source C. If the judgment result is yes, reference sources A and B are turned off and step 6 is executed. If the judgment result is no, step 5 is executed. Step 5: The control module calculates the calibration value based on the still-running reference source and stores the calculated calibration value in non-volatile memory; Step Six: Output one of the following three results: normal, single-source drift alarm, or common-mode drift, and continue to run the temperature measurement circuit. Calibrate the electrical signal of the temperature measurement circuit according to the calibration value in the non-volatile memory.

[0022] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A temperature controller with a built-in automatic calibration circuit for calibration based on a reference source, comprising, characterized in that: The system includes a control module, which is electrically connected to a sensor signal measurement module, a reference signal production module, and a reference source verification module. The reference source verification module includes reference source A and reference source B. The reference source verification module is used to output reference source voltages Va and Vb to the control module. The control module determines whether the reference source is abnormal based on the two voltages. When an abnormality is detected, the control module outputs an external reference source signal to shut down the abnormal reference source and issues a single-source drift alarm. The reference source is used to output a reference voltage to the reference signal production module. The sensor signal measurement module is used to connect to the temperature sensor of the temperature controller. The reference signal production module converts the reference voltage into a reference signal and uploads it to the control module, which is used to calculate the calibration value based on the reference signal. The control module is also equipped with an internal reference source C. The reference source verification module is used to output the reference source C voltage Vc to the control module. When the control module determines that the reference source is not abnormal based on the two voltages, it determines whether the reference source A is abnormal based on the two voltages Va and Vc. When it determines that an abnormality has occurred, it shuts down the reference sources A and B and issues a dual-source drift alarm. The reference source C is the internal bandgap reference voltage of the control module.

2. The temperature controller with built-in automatic calibration circuit based on a reference source according to claim 1, characterized in that: It also includes a sensing module, which is electrically connected to the control module. The sensing module is used to collect the internal temperature of the control module. The control module determines whether the temperature deviates from the standard value and corrects the reference signal when the determination result is yes.

3. The temperature controller with built-in automatic calibration circuit based on a reference source according to claim 2, characterized in that: The control module adds a correction coefficient A1 to the reference signal, where A1 = k1 × (T / T0) + c1, and k1 and c1 are pre-input constants, and T0 is a pre-input temperature standard value.

4. The temperature controller with built-in automatic calibration circuit based on a reference source as described in claim 3, characterized in that: The sensing module is also used to measure the power supply voltage of the control module and upload it to the control module. The control module determines whether the power supply voltage deviates from the standard value, and further corrects the reference signal when the determination result is yes.

5. The temperature controller with built-in automatic calibration circuit based on a reference source according to claim 4, characterized in that: The control module adds a correction coefficient A2 to the reference signal, where A2 = k2 × (V / V0) + c2, and k2 and c2 are pre-input constants, and V0 is the pre-input nominal power supply voltage.

6. The temperature controller with built-in automatic calibration circuit based on a reference source according to claim 5, characterized in that: It also includes a human-computer interaction module, which is electrically connected to the control module. The human-computer interaction module is used to display single-source drift alarms and dual-source drift alarms.

7. A calibration method for a temperature controller with a built-in automatic calibration circuit and a reference source for calibration, comprising the following steps: Step 1: Set up reference source A, reference source B and reference source C, set the automatic calibration conditions and start the temperature measurement circuit; Step 2: When the automatic calibration conditions are met, start the calibration and compare reference source A and reference source B. If the comparison result shows an abnormal difference between the two, proceed to step 3; otherwise, proceed to step 4. Step 3: Determine which of the reference sources, A and B, is abnormal. After the determination is complete, turn off the abnormal reference source and proceed to Step 5. Step 4: The control module determines whether dual-source drift has occurred by judging whether the voltage of reference source A is abnormal based on reference source C. If the judgment result is yes, reference sources A and B are turned off and step 6 is executed. If the judgment result is no, step 5 is executed. Step 5: The control module calculates the calibration value based on the still-running reference source and stores the calculated calibration value in non-volatile memory; Step Six: Output one of the following three results: normal, single-source drift alarm, or common-mode drift, and continue to run the temperature measurement circuit. Calibrate the electrical signal of the temperature measurement circuit according to the calibration value in the non-volatile memory.

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