On-line temperature self-compensating circuit of transmitter for force measurement

Abstract

The utility model relates to the technical field of on-site data acquisition, in particular to an on-line temperature self-compensating circuit of a transmitter for force measurement. The temperature self-compensating circuit comprises a double-path precision constant current source module which is composed of a high-precision reference voltage source, an operational amplifier and a sampling resistor and is used for providing equivalent excitation current for a working strain gauge and a temperature compensating gauge; the signal acquisition module comprises an embedded MCU and an external signal conditioning chip, a 24-bit ADC is integrated in the MCU and used for acquiring differential voltage signals of the working strain gauge, and a 24-bit ADC of the external signal conditioning chip is used for synchronously acquiring differential voltage signals of the temperature compensation gauge. According to the utility model, the temperature drift interference introduced by the adjustment of a traditional potentiometer is eliminated from the circuit level through the symmetric excitation architecture of the double-path precise constant current source module and the differential decoupling design of the synchronous ADC signal acquisition module.

Description

Technical Field

[0001] This utility model relates to the field of field data acquisition technology, specifically to an online temperature self-compensation circuit for a force measuring transmitter. Background Technology

[0002] Existing temperature compensation circuits for force transmitters generally rely on the physical adjustment structure of analog potentiometers. The temperature drift characteristics of these potentiometers easily introduce additional errors, leading to long-term stability degradation of the sensor signal conditioning circuit. Traditional circuits employ a single-channel excitation and static compensation design, requiring repeated adjustments of bridge parameters over a wide temperature range. The calibration process relies on manual intervention and lacks dynamic response, making it difficult to cope with nonlinear interference from transient temperature changes in industrial environments. Especially in high-precision scenarios, the cross-coupling between strain gauge resistance drift caused by temperature gradients and the transmitter signal path in existing circuits results in decreased compensation accuracy and calibration efficiency. Although attempts have been made to improve temperature drift through redundant circuits or complex hardware configurations, the fixed compensation coefficient and the hysteresis of the analog calibration loop limit the ability of existing circuits to achieve real-time self-compensation and rapid calibration coordination in dynamic temperature fields. Utility Model Content

[0003] This disclosure proposes an online temperature self-compensation circuit for a force transmitter, with the aim of overcoming at least one of the defects existing in the prior art.

[0004] To achieve the above objectives, the technical solution disclosed in this utility model is as follows:

[0005] According to one aspect of this disclosure, an online temperature self-compensation circuit for a force transmitter is provided, the temperature self-compensation circuit comprising:

[0006] The dual-channel precision constant current source module consists of a high-precision reference voltage source, an operational amplifier, and a sampling resistor, and is used to provide equivalent excitation current to the working strain gauge and the temperature compensation gauge.

[0007] The signal acquisition module includes an embedded MCU and an external signal conditioning chip. The MCU integrates a 24-bit ADC for acquiring the differential voltage signal of the working strain gauge, and the external signal conditioning chip has a 24-bit ADC for synchronously acquiring the differential voltage signal of the temperature compensation plate.

[0008] The transmitter output module includes a 16-bit DAC, a V / V conversion circuit, and a V / I conversion circuit. The output terminal of the DAC is connected to a voltage follower composed of operational amplifiers, and generates voltage transmission signals through the V / V conversion circuit and current transmission signals through the mirror current source circuit.

[0009] The feedback calibration module, including a multi-channel analog switch and a voltage divider sampling circuit, is used to feed back the voltage or current transmission signal to the MCU's internal ADC.

[0010] The power supply module, consisting of an LDO regulator, a π-type filter circuit, and transient suppression diodes, provides isolated power to the constant current source, MCU, and transmitter output module.

[0011] Furthermore, in the dual-channel precision constant current source module, each constant current source includes:

[0012] A reference voltage source, the output of which is connected to the non-inverting input of an operational amplifier;

[0013] The inverting input of the operational amplifier is connected to one end of the sampling resistor, and the output drives the base of the bipolar transistor.

[0014] The emitter of the bipolar transistor is connected to the other end of the sampling resistor and serves as a constant current output terminal, while the collector is connected to a working strain gauge or a temperature compensation gauge.

[0015] Furthermore, the V / I conversion circuit includes:

[0016] A voltage follower, whose input is connected to the output of a DAC, and whose output is connected to a current mirror source consisting of an operational amplifier, a bipolar transistor, and a sampling resistor;

[0017] The two ends of the sampling resistor are connected to a differential amplifier, and its output is fed back to the ADC inside the MCU after being switched by an analog switch.

[0018] Furthermore, the multi-channel analog switch in the feedback calibration module is a single-pole double-throw type. Its common terminal is connected to the current transmitter signal sampling resistor, the first switching terminal is connected to the current output path, and the second switching terminal is connected to the input terminal of the differential amplifier. The output terminal of the differential amplifier is connected to the ADC inside the MCU through an RC filter circuit.

[0019] Furthermore, in the power module, the analog power supply and the digital power supply are isolated by a ferrite bead, and the analog ground is connected to the digital ground at a single point through a 0Ω resistor; the π-type filter circuit is composed of an inductor and parallel ceramic capacitors and electrolytic capacitors, and its input terminal is connected in series with a resettable fuse and a reverse connection protection diode.

[0020] Furthermore, the GPIO pins of the embedded MCU are connected to a 4-bit DIP switch and a calibration button. The encoding state of the DIP switch is input to the input capture channel of the MCU through a pull-up resistor. The trigger signal of the calibration button is processed by a debouncing circuit to trigger an interrupt service routine.

[0021] Furthermore, in the signal acquisition module, the differential voltage signal of the working strain gauge is input to the 24-bit ADC inside the MCU via an RC low-pass filter, and the differential voltage signal of the temperature compensation plate is amplified by an instrumentation amplifier and then input to the 24-bit ADC of an external signal conditioning chip.

[0022] Furthermore, the V / V conversion circuit of the transmitter output module is composed of an operational amplifier and a precision resistor network, with a transient suppression diode connected in series at the output terminal; the mirror current source output terminal of the V / I conversion circuit is connected in series with an overcurrent protection transistor and a temperature compensation resistor.

[0023] The beneficial effects of this utility model are:

[0024] This invention eliminates temperature drift interference introduced by traditional potentiometer adjustment at the circuit level through a symmetrical excitation architecture of a dual-channel precision constant current source module combined with a differential decoupling design of a synchronous ADC signal acquisition module. The closed-loop feedback control circuit of the embedded MCU and the transmitter output module replaces analog adjustment with digital calibration, achieving dynamic compensation of the high-precision transmitter signal. The closed-loop dynamic adjustment mechanism of the dual constant current sources and the isolation filtering design of the power supply module suppress cross-interference between multiple signal paths. The isolated routing structure of the V / V and V / I conversion circuits, combined with the real-time sampling loop of the feedback calibration module, ensures the long-term stability of the transmitter signal over a wide temperature range. The synergistic optimization of each module significantly improves the circuit's temperature adaptability and solves the nonlinear accumulation problem caused by the fixed compensation mode and analog calibration lag in traditional circuits.

[0025] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a flowchart of the online temperature self-compensation calibration method for the force transmitter of this utility model;

[0027] Figure 2 This is a schematic diagram illustrating the online temperature self-compensation principle of this utility model;

[0028] Figure 3 This is a schematic diagram illustrating the principle of online self-calibration of analog transmission signals according to this utility model;

[0029] Figure 4 This is a system hardware block diagram illustrating the functionality of this utility model;

[0030] Figure 5 This is the system power supply circuit that enables the functions of this utility model;

[0031] Figure 6 This is the circuit diagram of the dual constant current excitation working strain gauge and temperature compensator of this utility model;

[0032] Figure 7 This is the MCU minimum system and related peripheral circuit diagram of this utility model;

[0033] Figure 8 This utility model relates to an analog signal transmission output and real-time acquisition circuit. Detailed Implementation

[0034] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0035] The term "comprising," and any variations thereof, used in the specification and claims of this application, is intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus. Furthermore, the use of "and / or" in the specification and claims indicates at least one of the connected objects, such as A and / or B, indicating the inclusion of A alone, B alone, or both A and B.

[0036] The present invention provides the following preferred embodiments:

[0037] Example 1

[0038] To address the issues of insufficient temperature drift suppression caused by the hysteresis of fixed compensation parameters in dynamic temperature fields and the low efficiency of manual calibration, this embodiment further optimizes the collaborative mechanism of dual-channel constant current source excitation, synchronous signal acquisition, and dynamic weighted compensation. For example... Figure 1 As shown, the steps of the online temperature self-compensation calibration method for force transmitters are as follows:

[0039] S100: The working strain gauge and the temperature compensation gauge are synchronously excited by dual precision constant current sources. The working strain gauge and the temperature compensation gauge have the same material parameters and are in the same temperature field. The output current values ​​of the dual constant current sources are equal and are controlled by a high-precision reference voltage source and sampling resistor in a closed loop.

[0040] S200: Synchronously acquire the differential voltage signal of the working strain gauge and the differential voltage signal of the temperature compensation gauge, and perform synchronous analog-to-digital conversion through the 24-bit ADC integrated in the embedded MCU and the 24-bit ADC of the external signal conditioning chip, respectively, to obtain the first conversion result AD_Result_work and the second conversion result AD_Result_temp.

[0041] S300: Based on the second conversion result AD_Result_temp, the first conversion result AD_Result_work is subjected to real-time temperature compensation through a dynamic weighting algorithm to generate the compensated output value AD_Compensated. The dynamic weighting algorithm adjusts the temperature influence coefficient according to the gradient change of the second conversion result AD_Result_temp.

[0042] S400: Controls the target voltage output of the 16-bit DAC to the V / V conversion circuit and V / I conversion circuit through the embedded MCU, generating isolated voltage and current transmission signals.

[0043] S500: In response to zero-point calibration or full-scale calibration commands, the voltage or current transmission signal is fed back to the ADC inside the MCU in real time for sampling, and the DAC output value is dynamically adjusted through an incremental PID algorithm until the error between the feedback signal and the preset target value is less than 0.02%FS, thus completing the online calibration.

[0044] Specifically, a dual constant current source circuit driven by a high-precision reference voltage source ADR4340 is adopted. Its output currents I1+ and I2+ are stabilized within an accuracy range of 5.000mA ± 0.02% through closed-loop feedback control. The core of the constant current source consists of a low-noise operational amplifier OPA2188 and a precision sampling resistor RS2 (resistance value 500Ω ± 0.01%). By real-time monitoring of the voltage drop across the sampling resistor and differential comparison with the 2.500V reference output from the ADR4340, the driving voltage of the operational amplifier is dynamically adjusted to ensure the long-term stability of the constant current source. The working strain gauge and temperature compensation gauge are both KFG-5-350-C1-23 type strain gauges from the same batch, with a temperature coefficient of ±3ppm / ℃. An epoxy resin encapsulation process ensures that both are on the same heat conduction path, thereby eliminating compensation errors introduced by uneven temperature field distribution.

[0045] Furthermore, the embedded MCU uses the ADuCM360 with a built-in 24-bit Σ-Δ ADC. Its differential input channels AIN0-AIN1 synchronously acquire the differential voltage signal (Vp-Vn) of the working strain gauge at a rate of 2400 samples per second. Simultaneously, it controls the ADC channel of the external signal conditioning chip NSA2860 via the SPI bus to acquire the differential voltage signal (Vt±Vt-) of the temperature compensation chip at the same rate. To achieve strict synchronous acquisition, the ADC start signal of the ADuCM360 and the CONVST pin of the NSA2860 are linked by a hardware trigger signal to ensure that the sampling time deviation between the two ADCs is less than 1μs. The acquired first conversion result AD_Result_work and second conversion result AD_Result_temp are stored in a circular buffer and compensated in real time using a dynamic weighting algorithm. It is important to understand that the dynamic weighting algorithm is not a simple static subtraction of the two signals, but rather an adaptive adjustment of the weight of the temperature sensitivity matching coefficient α based on the gradient change (ΔT / Δt) of AD_Result_temp. For example, when the temperature change rate ΔT / Δt ≥ 0.5℃ / s, the algorithm increases α from the calibrated value of 0.98 to 1.05 to compensate for the signal tracking delay caused by thermal inertia when the temperature changes rapidly; when ΔT / Δt ≤ 0.1℃ / s, the calibrated value of α = 0.98 is restored, thereby achieving a compensation accuracy better than ±0.05%FS in both transient and steady-state temperature fields.

[0046] Furthermore, the compensated output value AD_Compensated is converted into an analog voltage by the 16-bit DAC module (model DAC80508) integrated within the ADuCM360, and then output as a 0-5V standard signal via a V / V conversion circuit. The V / V conversion circuit uses a non-inverting amplifier built with a zero-drift operational amplifier LTC2057, with its gain set to 2.000±0.01% by a precision resistor network, while suppressing nonlinear distortion through a negative feedback loop. For the current transmission signal output, the DAC output signal is isolated by a voltage follower composed of LTC2057, and then fed into a V / I conversion circuit composed of a precision instrumentation amplifier INA188 and MOSFET transistors, outputting a 4-20mA current signal. It is important to understand that the voltage follower ensures impedance matching and isolation between the voltage and current output paths, avoiding signal crosstalk caused by load changes.

[0047] Furthermore, during online calibration, when the user selects the voltage output mode via a DIP switch and triggers zero-point calibration, the ADuCM360 initializes the DAC output to 0V and activates the internal ADC channel AIN4 to sample the Vout signal in real time. The incremental PID algorithm dynamically adjusts the DAC output code based on the deviation e(k) between the sampled value and the target value of 0V. Specifically, the proportional gain Kp of the PID controller adopts a two-stage adjustment strategy: in the initial adjustment stage (|e(k)|>0.5%FS), Kp=3.0 to accelerate the response speed; when the deviation enters the steady-state range (|e(k)|≤0.5%FS), Kp switches to 0.5 to suppress overshoot. The integral time Ti and derivative time Td are dynamically coupled according to the temperature-compensated AD_Compensated value. For example, when AD_Compensated>80%FS, Ti is shortened from the default 5ms to 3ms, and Td is extended from 0.5ms to 1ms to cope with nonlinear errors caused by sudden load changes. Through the above adjustment mechanism, the convergence time of zero-point calibration can be shortened to less than 35ms, and the steady-state error can be controlled within ±0.01%FS.

[0048] The advantages of this embodiment are as follows: The closed-loop dynamic control and synchronous acquisition mechanism using dual constant current sources eliminates the drawbacks of temperature drift caused by traditional potentiometer adjustment and the low efficiency of manual calibration; the dynamic weighted algorithm combined with adaptive adjustment of the compensation coefficient based on the rate of temperature change solves the hysteresis problem of fixed compensation parameters in transient temperature fields; the multi-stage adjustment strategy of the incremental PID algorithm significantly improves the response speed while ensuring calibration accuracy. Furthermore, the isolation design of the voltage and current output paths ensures the independence and consistency of the two transmission signals across the entire range.

[0049] Example 2

[0050] In this embodiment, as Figure 2 The schematic diagram shown illustrates the principle of online temperature self-compensation. It generates two precision constant current sources, I1+ and I2+, both with the same current magnitude, typically around 5mA. Due to the constant current excitation, the voltage drop generated by the strain gauges is a single-valued function of their resistance. When the two working strain gauges are operating, one is under tension and the other under compression, and their resistances change in opposite directions. Figure 1As shown, the differential voltage of the two working strain gauges is acquired, conditioned, and then sent to the 24-bit ADC inside the MCU for AD conversion. Let the AD conversion result be AD_Result_wort. Two temperature compensation gauges are used, employing the same strain gauges as the working strain gauges or dedicated temperature compensation gauges. Besides adjusting for deviations caused by the asynchronous operation of the two constant currents, their main function is temperature compensation. Their resistance changes are only affected by temperature. Since the working strain gauges and temperature compensation gauges have the same performance and are located in the same temperature field, the resistance changes caused by temperature changes in the working strain gauges and the temperature compensation gauges are essentially the same. The differential signal from the two temperature compensation strain gauges is sent to the 24-bit ADC for AD conversion. Let the conversion result be AD_Result_tempt, which is obtained by the MCU. The difference between AD_Result_wort and AD_Result_tempt is used as the final sensor output signal conversion value. Because the two are synchronous AD conversion results, the difference between their conversion values ​​essentially eliminates sensor signal changes caused by temperature variations, thus achieving online temperature self-compensation.

[0051] Furthermore, such as Figure 3 The schematic diagram shown illustrates the principle of online self-calibration of analog transmission signals. Output selection is set by a DIP switch. The analog transmission signal output can be a single current or voltage transmission signal, or simultaneously output standard voltage and current transmission signals. A 16-bit DAC, under the control of the MCU, outputs relevant voltage signals. One path sends a voltage transmission signal to a V / V converter. After voltage tracking of the DAC output voltage, it is sent to a V / I converter to output an analog current transmission signal. Voltage tracking ensures that the two transmission signals do not interfere with each other when outputting simultaneously. Taking 0-5V output as an example, when zero-point calibration is required, the output and calibration type are selected as 0-5V via the DIP switch. Pressing the zero-calibration button sends the real-time output of the voltage transmission signal to the MCU's internal 24-bit ADC for AD conversion. Based on the preset zero-point calibration target value, the PID control program embedded in the MCU automatically completes the zero-point calibration, outputting 0V. When full-scale calibration is required, simply press the full-scale calibration button; similarly, the PID control program automatically completes the full-scale calibration, outputting 5V. Other calibrations are similar.

[0052] Furthermore, such as Figure 4The system hardware block diagram shown illustrates the functionality of this invention. The system is powered by a 24VDC power supply, which, after voltage regulation, powers each module. The sensors are excited by dual precision constant current sources. The differential signal from the working strain gauge is converted by a high-resolution ADC integrated within the MCU. The differential signal from the temperature compensation gauge is synchronously converted by an external 24-bit ADC, and the MCU reads the conversion result. The MCU controls a 16-bit DAC to perform corresponding digital-to-analog conversion and outputs corresponding current and voltage analog transmission signals through V / I and V / V stages. The system is equipped with a 4-bit DIP switch for selecting the analog transmission signal output type, and two independent buttons for zero-point calibration and full-scale calibration. Based on the output type selection, pressing the relevant button activates the corresponding output calibration using a PID program embedded in the MCU's internal FLASH memory.

[0053] Furthermore, such as Figure 5 The system power supply circuit uses a 24V DC power supply. D1 is a transient suppression diode, which can realize surge protection and overvoltage protection. F1 is a self-resetting fuse, which can realize system overcurrent protection. D2 is a reverse connection protection diode. The LDO Zener diode U4 provides a 3.3V power supply VCC to power the MCU and other digital circuits. U5 generates a 5V analog power supply 5VA to power the operational amplifier and reference chip, etc. U3 generates a 3.3V analog power supply to provide analog power to the MCU and external ADC / DAC chip NSA2860, etc. The analog ground and digital ground of the system are routed separately to prevent digital circuits from interfering with analog circuits. Then, a 0-ohm resistor R1 connects the analog ground and digital ground at one point to ensure that the potentials of digital ground and analog ground are the same.

[0054] Furthermore, such as Figure 6 The circuit diagram for the dual constant current excitation of the working strain gauge and temperature compensation plate is shown below. Taking the circuit generating the first I1+ as an example, U10, R14, R15, R18, R20, and RS2 form a constant current circuit, where R15 = R18 = R14 = R20, and RS2 is a sampling resistor. The generated constant current I1+ = 2.5V / RS2. The magnitude of the constant current can be obtained by appropriately selecting the resistance value of RS2, which is generally around 5mA. The 2.5V reference voltage is obtained from the high-precision reference chip U11. In the design, I1+ and I2+ are equal. The two constant currents drive the two working strain gauges and the temperature compensation plate. The differential voltage S+-S- of the working strain gauges, after filtering and limiting, yields the Vp-Vn differential signal, which is sent to the 24-bit ADC inside the MCU for AD conversion. The differential signal Vt+-Vt- of the compensation plate is sent to the external NSA2860's internal 24-bit ADC for conversion. The two processes are performed synchronously.

[0055] Furthermore, such as Figure 7The diagram shows the minimum system of the MCU and related peripheral circuits of this invention. U9 in the diagram is the MCU, a domestically produced high-performance analog-mixed device. It integrates a multi-channel, high-resolution 24-bit ADC and a low-noise programmable gain amplifier (PGA). The differential signal from the sensor's strain gauge is sent to its internal AIN0-AIN1 differential channels. During calibration, the relevant analog transmission signals are processed and sent to AIN4 and AIN5 channels for AD conversion. The PID control program is stored in the MCU's internal FLASH memory. The MCU and the external NSA2860 communicate via the SPI bus. SW1 is a 4-bit DIP switch used for output type selection and calibration selection. R26 and C27 are the power-on reset circuit. S1 and S2 are the full-scale calibration and zero-point calibration function keys, respectively. S3 is the zeroing key; pressing this key during operation performs a zeroing operation. DS1 is a status indicator used to display the transmitter's operating status.

[0056] Furthermore, such as Figure 8 The circuit shown depicts the analog signal transmission output and real-time acquisition. U3 is an analog mixed-signal device integrating a 24-bit ADC and a 16-bit DAC, as well as a PGA with amplification ranging from 1x to 256x. Its ADC performs AD conversion on the differential signals Vt+-Vt- from the temperature compensation chip, and the 16-bit DAC generates the corresponding analog voltage output. This is amplified and converted by the low-noise operational amplifier U1 to produce the analog voltage transmission signal output Vout. The output voltage V_DET is then obtained by voltage division through precision low-drift resistors RS_V1 and RS_V2 and sent to the MCU's internal AIN4 channel for feedback, used for PID regulation and calibration of the analog voltage transmission output signal. The voltage from U2 is followed by a precision V / I converter circuit composed of U7, Q3, Q4, R10, and R13 to generate the analog current transmission signal output. U8 is a single-pole double-throw analog switch. When a normal current transmission signal is required, B-A2 is turned on, outputting the current transmission signal IOUT. When calibration of this signal is required, the MCU controls pin 6 of U8 to turn on B-A1. U12 follows the signal, and then the current-to-voltage conversion is achieved by the RS1 sampling resistor. The signal is then sent to the AIN5 channel of the MCU's internal ADC for acquisition and feedback. Automatic calibration of the current transmission signal is achieved by a PID controller. R12 and Q4 in the diagram form a current-limiting resistor. The current limiting value depends on the resistance of R12. R13 and R10 are precision resistors with a strength of 0.1% (25ppm). The current and voltage transmission output signals in the diagram can be output individually or simultaneously. Due to the presence of the voltage follower U2, the two do not affect each other. D3 acts as a reverse protection device. The voltage follower formed by U12 is used to eliminate the influence of the analog switch's on-resistance (approximately 1 ohm) on the current sampling.

[0057] Although the present invention has been specifically described above with reference to preferred embodiments, it should be understood that the present invention is not limited to the embodiments described above. Rather, various modifications and variations can be made by those skilled in the art without departing from the essence of the present invention, and such modifications and variations should fall within the scope defined by the appended claims and their equivalents.

Claims

1. An online temperature self-compensation circuit for a force measuring transmitter, characterized in that, The temperature self-compensation circuit includes: The dual-channel precision constant current source module consists of a high-precision reference voltage source, an operational amplifier, and a sampling resistor, and is used to provide equivalent excitation current to the working strain gauge and the temperature compensation gauge. The signal acquisition module includes an embedded MCU and an external signal conditioning chip. The MCU integrates a 24-bit ADC for acquiring the differential voltage signal of the working strain gauge, and the external signal conditioning chip has a 24-bit ADC for synchronously acquiring the differential voltage signal of the temperature compensation plate. The transmitter output module includes a 16-bit DAC, a V / V conversion circuit, and a V / I conversion circuit. The output terminal of the DAC is connected to a voltage follower composed of operational amplifiers, and generates voltage transmission signals through the V / V conversion circuit and current transmission signals through the mirror current source circuit. The feedback calibration module, including a multi-channel analog switch and a voltage divider sampling circuit, is used to feed back the voltage or current transmission signal to the MCU's internal ADC. The power supply module, consisting of an LDO regulator, a π-type filter circuit, and transient suppression diodes, provides isolated power to the constant current source, MCU, and transmitter output module.

2. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, In the dual-channel precision constant current source module, each constant current source includes: A reference voltage source, the output of which is connected to the non-inverting input of an operational amplifier; The inverting input of the operational amplifier is connected to one end of the sampling resistor, and the output drives the base of the bipolar transistor. The emitter of the bipolar transistor is connected to the other end of the sampling resistor and serves as a constant current output terminal, while the collector is connected to a working strain gauge or a temperature compensation gauge.

3. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, The V / I conversion circuit includes: A voltage follower, whose input is connected to the output of a DAC, and whose output is connected to a current mirror source consisting of an operational amplifier, a bipolar transistor, and a sampling resistor; The two ends of the sampling resistor are connected to a differential amplifier, and its output is fed back to the ADC inside the MCU after being switched by an analog switch.

4. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, The multi-channel analog switch in the feedback calibration module is a single-pole double-throw type. Its common terminal is connected to the current transmitter signal sampling resistor, the first switching terminal is connected to the current output path, and the second switching terminal is connected to the input terminal of the differential amplifier. The output terminal of the differential amplifier is connected to the ADC inside the MCU through an RC filter circuit.

5. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, In the power supply module, the analog power supply and the digital power supply are isolated by a ferrite bead, and the analog ground is connected to the digital ground at a single point through a 0Ω resistor; the π-type filter circuit is composed of an inductor and parallel ceramic capacitors and electrolytic capacitors, and its input terminal is connected in series with a resettable fuse and a reverse connection protection diode.

6. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, The GPIO pins of the embedded MCU are connected to a 4-bit DIP switch and a calibration button. The encoding state of the DIP switch is input to the input capture channel of the MCU through a pull-up resistor. The trigger signal of the calibration button is processed by a debouncing circuit to trigger an interrupt service routine.

7. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, In the signal acquisition module, the differential voltage signal of the working strain gauge is input to the 24-bit ADC inside the MCU through an RC low-pass filter, and the differential voltage signal of the temperature compensation plate is amplified by an instrumentation amplifier and then input to the 24-bit ADC of the external signal conditioning chip.

8. The online temperature self-compensation circuit for a force transmitter according to claim 1, characterized in that, The V / V conversion circuit of the transmitter output module consists of an operational amplifier and a precision resistor network, with a transient suppression diode connected in series at the output terminal; the output terminal of the V / I conversion circuit's mirror current source is connected in series with an overcurrent protection transistor and a temperature compensation resistor.

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