Nuclear measurement analog quantity transmission method based on feedback compensation circuit

Abstract

The invention relates to the technical field of nuclear radiation detection, and provides a nuclear measurement analog quantity transmission method based on a feedback compensation circuit, and a hardware part used in the method comprises an ARM chip, a digital-to-analog converter, a digital potentiometer, an operational amplifier, an isolated voltage-to-current converter, an isolation chip and an A / D conversion chip. The ARM chip is respectively connected with the digital-to-analog converter and the digital potentiometer, the ARM chip is connected with the A / D conversion chip after passing through the isolation chip, the first operational amplifier is respectively connected with the digital-to-analog converter, the digital potentiometer and the isolation type voltage and current converter, and the second operational amplifier is connected with the isolation type voltage and current converter. And the output current of the isolated voltage-current converter is connected with the A / D conversion chip through the precision resistor and the second operational amplifier. According to the comparison result of the output signal and the input signal, the output current can be corrected in time by adopting a mode of adjusting the input signal through feedback compensation, and the output accuracy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear radiation detection, in particular to a nuclear measurement analog quantity transmission method based on a feedback compensation circuit. Background Art

[0002] Analog transmission is one of the conventional hard-wired information exchange methods, with the characteristics of fast response, high reliability and low failure rate. At present, the digital instrumentation and control system (DCS) of nuclear power plants still uses hard wiring in large quantities, and some channels with higher importance require analog transmission of information.

[0003] In the process of nuclear radiation monitoring, the signal processing unit usually completes the nuclear measurement data processing and analog output. The analog quantity is generally 4mA ~ 20mA current, corresponding to the range of the measurement value. The accuracy of the analog quantity determines the accuracy of the transmitted data.

[0004] The analog quantity is generated by the digital-to-analog converter and the isolated voltage-to-current converter, so it is inevitable that there will be a certain amount of nonlinear error. In some special application scenarios, the output current accuracy cannot meet the technical requirements and compensation correction is required. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and to provide a nuclear measurement analog quantity transmission method based on a feedback compensation circuit. This method uses feedback compensation to adjust the input signal according to the comparison result of the output signal and the input signal, so as to correct the output current in time and improve the output accuracy.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A nuclear measurement analog quantity transmission method based on a feedback compensation circuit, the hardware parts used in the method include an ARM chip, a digital-to-analog converter, a digital potentiometer, a first operational amplifier, an isolated voltage-current converter, an isolation chip, an A / D conversion chip, a precision resistor, a second operational amplifier, etc.

[0008] The ARM chip is respectively connected to the digital-to-analog converter and the digital potentiometer. The ARM chip is connected to the A / D conversion chip after passing through the isolation chip. The first operational amplifier is respectively connected to the digital-to-analog converter, the digital potentiometer, and the isolated voltage-current converter. The output current of the isolated voltage-current converter is connected to the A / D conversion chip through a precision resistor and a second operational amplifier.

[0009] The method comprises the following steps:

[0010] (1) The program is initialized, each chip is initialized, and the initial resistance value of the digital potentiometer is set to the minimum value.

[0011] (2) When powered on for the first time, the corresponding magnifications of the first operational amplifier circuit at the 256 tap positions of the digital potentiometer are stored in sequence in the internal storage module of the ARM chip. This operation is not required for subsequent work.

[0012] The specific operations are as follows:

[0013] (2-1) The ARM chip sets the core measurement analog output current value I to be 12mA, the middle value of the current range of 4mA to 20mA. The digital-to-analog converter output voltage value V is converted to 2.5V, the middle value of the voltage range of 0V to 5V, through the corresponding relationship. The conversion formula is: V = (I-4) * 5 / 16;

[0014] (2-2) Based on the digital-to-analog converter communication protocol, send a command to control the digital-to-analog converter to output a voltage value of 2.5V as the input of the first operational amplifier; measure the voltage value across the precision resistor through the A / D conversion chip, and convert it to obtain the final output analog value;

[0015] (2-3) Based on the digital potentiometer communication protocol, the ARM chip sends a control command to adjust the resistance value of the digital potentiometer. The command range is 0x00 to 0xFF. 0x00 corresponds to the minimum resistance value, so the first operational amplifier circuit has the smallest amplification factor. 0xFF corresponds to the maximum resistance value, so the first operational amplifier circuit has the largest amplification factor.

[0016] (2-4) Compare the output analog quantity and the set analog quantity to obtain the system amplification factor. Finally, the ARM chip stores the amplification factors corresponding to the 256 tap positions of the digital potentiometer in the internal storage module.

[0017] (3) In normal operation, the ARM program uses feedback and compensation to correct the output current value. The specific operation is as follows:

[0018] (3-1) After converting the nuclear measurement value into 4mA to 20mA analog quantity according to the specified range and conversion formula, the output voltage value is obtained and the output of the digital-to-analog converter is controlled;

[0019] (3-2) Use the feedback circuit composed of precision resistors and A / D conversion chip to measure the error between the output analog quantity and the analog quantity converted by the ARM program;

[0020] (3-3) If the error exceeds the specified range, calculate the target gain m = converted analog value a / output analog value b, use the ARM program to query the gain storage array corresponding to the tap position, find the tap position closest to the target gain, write the position into the digital potentiometer, and combine the ARM program to control the compensation circuit composed of the digital potentiometer and the first operational amplifier to perform real-time compensation for the output current.

[0021] In the above technical solution, the ARM chip adopts the GD32F450 chip, and the operating voltage is +3.3V. The SPI interface isolation chip adopts the ADuM1411 chip. The isolation chip completes the SPI interface isolation between the ARM chip and the A / D conversion chip, and improves the anti-interference performance of the transmission signal.

[0022] In the above technical solution, the current output circuit is composed of the digital-to-analog converter AD5663, the first operational amplifier TLE2072, the isolated voltage-to-current converter 1B22, capacitors, and resistors. The digital-to-analog converter SPI interface is connected to the ARM chip through the isolation chip; the digital-to-analog converter output voltage is used as the input of the first operational amplifier; and the output of the first operational amplifier is used as the input of the voltage-to-current converter.

[0023] In the above technical solution, the feedback circuit is composed of a precision resistor with a tolerance of ±0.01%, a second operational amplifier TLE2072, an A / D conversion chip AD7327, and an SPI interface isolation chip ADuM1411. The voltage across the precision resistor is followed and processed by the second operational amplifier TLE2072 and then input to the A / D conversion chip; the SPI interface of the A / D conversion chip is connected to the ARM chip through the isolation chip. The precision resistor has a resistance of 100Ω. The second operational amplifier is used as a voltage follower.

[0024] In the above technical solution, the compensation circuit is composed of the first operational amplifier TLE2072, the digital potentiometer CL4801, the capacitor, and the resistor; the digital potentiometer SPI interface is connected to the ARM chip. The CL4801 chip is a 10kΩ digital potentiometer that supports the SPI protocol and has 256 adjustable taps. The digital potentiometer is controlled by the ARM chip to change the amplification factor of the compensation circuit. The resistance value is 1MΩ. The amplification factor range of the compensation circuit is controlled to be 0-1%.

[0025] The nuclear measurement analog quantity transmission method based on the feedback compensation circuit of the present invention adopts the feedback compensation to adjust the input signal and timely corrects the output current. Compared with the prior art, it has the following advantages:

[0026] 1. Analog transmission has certain feedback compensation adjustment capabilities and strong environmental adaptability;

[0027] 2. The analog transmission has small nonlinear error and high accuracy, which can meet the needs of more application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a connection block diagram of the hardware part in the method of the present invention.

[0029] Figure 2 This is a partial circuit connection diagram of the ARM chip in an embodiment of the present invention.

[0030] Figure 3 4 is a connection diagram of a current output circuit in an embodiment of the present invention.

[0031] Figure 4 4 is a connection diagram of a feedback circuit in an embodiment of the present invention.

[0032] Figure 5 FIG. 4 is a connection diagram of a compensation circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments.

[0034] like Figure 1 As shown, this embodiment provides a method for transmitting nuclear measurement analog quantity based on feedback compensation circuit, and the hardware part used in the method is composed of ARM chip, digital-to-analog converter, digital potentiometer, first operational amplifier, isolated voltage-current converter, isolation chip, A / D conversion chip, precision resistor, second operational amplifier, etc. The ARM chip is respectively connected to the digital-to-analog converter and the digital potentiometer, and the ARM chip is connected to the A / D conversion chip after the isolation chip, and the first operational amplifier is respectively connected to the digital-to-analog converter, the digital potentiometer, and the isolated voltage-current converter, and the output current of the isolated voltage-current converter is connected to the A / D conversion chip through the precision resistor and the second operational amplifier.

[0035] In the above embodiment, the ARM chip adopts the GD32F450 chip. The ARM chip directly controls the digital-to-analog converter and the digital potentiometer chip based on the SPI protocol; the A / D conversion chip is controlled by the isolation chip. The digital potentiometer adopts the CL4801 chip that supports the SPI protocol. Based on the SPI protocol, the control command (0x00~0xFF) is sent through the ARM chip encoding to control the resistance of the digital potentiometer. When the instruction is 0x00, the resistance value is the smallest and the corresponding magnification is the smallest; when the instruction is 0xFF, the resistance value is the largest and the corresponding magnification is the largest. When powered on for the first time, the magnification of the amplifier circuit at the 256 tap positions of the digital potentiometer needs to be stored in the internal storage module of the ARM chip in sequence.

[0036] like Figure 2 As shown in the figure, the ARM chip circuit consists of the ARM chip GD32F450, crystal oscillator, resistors, and capacitors. The ARM chip power pins are all connected to +3.3V, and the ground pins are all connected to GND; the first SPI interface pin is connected to the digital-to-analog converter; the second SPI interface pin is connected to the digital potentiometer; and the third SPI interface pin is connected to the isolation chip.

[0037] like Figure 3As shown, the current output circuit is composed of a digital-to-analog converter AD5663, a first operational amplifier TLE2072, an isolated voltage-to-current converter 1B22, capacitors, and resistors. The power supply voltage of 1B22 is ±15V. The output end is connected to a precision resistor.

[0038] like Figure 4 As shown in the figure, the feedback circuit part is composed of a precision resistor with a tolerance of ±0.01%, a second operational amplifier TLE2072, an A / D conversion chip AD7327, and an SPI interface isolation chip ADuM1411. The voltage across the precision resistor is followed and processed by the second operational amplifier TLE2072 and then input to the A / D conversion chip; the SPI interface of the A / D conversion chip is connected to the ARM chip through the isolation chip. The precision resistor has a resistance of 100Ω. The second operational amplifier is used as a voltage follower.

[0039] like Figure 5 As shown, the compensation circuit is composed of the first operational amplifier TLE2072, the digital potentiometer CL4801, capacitors, and resistors; the digital potentiometer SPI interface is connected to the ARM chip. The CL4801 chip is a 10kΩ digital potentiometer that supports the SPI protocol and has 256 adjustable taps. The digital potentiometer is controlled by the ARM chip to change the gain of the compensation circuit. The resistance value is 1MΩ. The gain range of the compensation circuit is controlled to be 0-1%.

[0040] This example provides a method for transmitting a nuclear measurement analog quantity based on a feedback compensation circuit, comprising the following steps:

[0041] (1) Initialize the program, initialize each chip, and set the initial resistance of the digital potentiometer to the minimum value;

[0042] (2) In the internal storage module of the ARM chip, the corresponding amplification factors of the first operational amplifier circuit at the 256 tap positions of the digital potentiometer are stored in sequence.

[0043] (3) After converting the nuclear measurement value into 4mA to 20mA analog quantity according to the specified range and conversion formula, the output voltage value is obtained and the output of the digital-to-analog converter is controlled;

[0044] (4) Use a feedback circuit composed of precision resistors and A / D conversion chips to measure the error between the output analog quantity and the analog quantity converted by the ARM program;

[0045] (5) If the error exceeds the specified range, the tap position of the digital potentiometer is adjusted using the ARM program, and the compensation circuit composed of the digital potentiometer and the first operational amplifier is controlled by the ARM program to perform real-time compensation on the output current, so that the output result meets the technical requirements.

[0046] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0047] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for transmitting nuclear measurement analog quantity based on feedback compensation circuit, characterized in that: The hardware part used in the method includes an ARM chip, a digital-to-analog converter, a digital potentiometer, a first operational amplifier, an isolated voltage-to-current converter, an isolation chip, an A / D conversion chip, a precision resistor, and a second operational amplifier. The ARM chip is respectively connected to the digital-to-analog converter and the digital potentiometer. The ARM chip is connected to the A / D conversion chip after passing through the isolation chip. The first operational amplifier is respectively connected to the digital-to-analog converter, the digital potentiometer, and the isolated voltage-to-current converter. The output current of the isolated voltage-to-current converter is connected to the A / D conversion chip through a precision resistor and the second operational amplifier. The method comprises the following steps: (1) Initialize the program, initialize each chip, and set the initial resistance of the digital potentiometer to the minimum value; (2) When the power is turned on for the first time, the corresponding magnifications of the first operational amplifier circuit at the 256 tap positions of the digital potentiometer are stored in sequence in the internal storage module of the ARM chip. This operation is not required for subsequent work. The specific operation is as follows: (2-1) The ARM chip sets the core measurement analog output current value I to be 12mA, the middle value of the current range of 4mA to 20mA. The digital-to-analog converter output voltage value V is converted to 2.5V, the middle value of the voltage range of 0V to 5V, through the corresponding relationship. The conversion formula is: V = (I-4) * 5 / 16; (2-2) Based on the digital-to-analog converter communication protocol, send a command to control the digital-to-analog converter to output a voltage value of 2.5V as the input of the first operational amplifier; measure the voltage value across the precision resistor through the A / D conversion chip, and convert it to obtain the final output analog value; (2-3) Based on the digital potentiometer communication protocol, the ARM chip sends a control command to adjust the resistance value of the digital potentiometer. The command range is 0x00 to 0xFF. 0x00 corresponds to the minimum resistance value, so the first operational amplifier circuit has the smallest amplification factor. 0xFF corresponds to the maximum resistance value, so the first operational amplifier circuit has the largest amplification factor. (2-4) Compare the output analog value and the set analog value to obtain the system amplification factor. Finally, the ARM chip stores the amplification factors corresponding to the 256 tap positions of the digital potentiometer in the internal storage module; (3) In normal operation, the ARM program uses feedback compensation to correct the output current value; the specific operation is as follows: (3-1) After converting the nuclear measurement value into 4mA to 20mA analog quantity according to the specified range and conversion formula, the output voltage value is obtained and the output of the digital-to-analog converter is controlled; (3-2) Use the feedback circuit composed of precision resistors and A / D conversion chip to measure the error between the output analog quantity and the analog quantity converted by the ARM program; (3-3) If the error exceeds the specified range, calculate the target gain m = converted analog value a / output analog value b, use the ARM program to query the gain storage array corresponding to the tap position, find the tap position closest to the target gain, write the position into the digital potentiometer, and combine the ARM program to control the compensation circuit composed of the digital potentiometer and the first operational amplifier to perform real-time compensation for the output current.

2. The method for transmitting nuclear measurement analog quantity based on feedback compensation circuit according to claim 1, characterized in that: The ARM chip adopts the GD32F450 chip, and the operating voltage is +3.3V.

3. The method for transmitting nuclear measurement analog quantity based on feedback compensation circuit according to claim 1, characterized in that: The current output circuit is composed of a digital-to-analog converter AD5663, a first operational amplifier TLE2072, an isolated voltage-to-current converter 1B22, a capacitor, and a resistor. The digital-to-analog converter SPI interface is connected to the ARM chip through an isolation chip. The output voltage of the digital-to-analog converter is used as the input of the first operational amplifier; and the output of the first operational amplifier is used as the input of the voltage-to-current converter.

4. The method for transmitting nuclear measurement analog quantity based on feedback compensation circuit according to claim 1, characterized in that: The feedback circuit is composed of a precision resistor with a tolerance of ±0.01%, a second operational amplifier TLE2072, an A / D conversion chip AD7327, and an SPI interface isolation chip ADuM1411. The voltage across the precision resistor is followed and processed by the second operational amplifier TLE2072 and then input to the A / D conversion chip; the SPI interface of the A / D conversion chip is connected to the ARM chip through the isolation chip.

5. The method for transmitting nuclear measurement analog quantity based on feedback compensation circuit according to claim 1, characterized in that: The compensation circuit is composed of a first operational amplifier TLE2072, a digital potentiometer CL4801, a capacitor and a resistor; and the digital potentiometer SPI interface is connected to the ARM chip.

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