CN114296019A - Temperature compensation structure of direct current sensor - Google Patents
Temperature compensation structure of direct current sensor Download PDFInfo
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- CN114296019A CN114296019A CN202111557635.8A CN202111557635A CN114296019A CN 114296019 A CN114296019 A CN 114296019A CN 202111557635 A CN202111557635 A CN 202111557635A CN 114296019 A CN114296019 A CN 114296019A
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Abstract
The invention relates to a temperature compensation structure of a direct current sensor, which is characterized in that: the electromagnetic induction module comprises a circular magnetic core with a gap, a coil is wound around the surface of the magnetic core, the coil is provided with a first coil interface and a second coil interface, the first coil interface and the second coil interface are respectively connected to the auxiliary circuit of the control chip, a square magnetic sensor with two output ports is placed at the gap, and the magnetic sensor is connected with the two ends of an operational amplifier through the output ports; the temperature sensor sampling circuit comprises a temperature-sensitive resistor and a divider resistor, one end of the temperature-sensitive resistor is grounded, the other end of the temperature-sensitive resistor is connected with the control chip, one end of the divider resistor is connected with the power supply, and the other end of the divider resistor is connected with the control chip. The external communication interface connects an external communication circuit to the control chip, can read temperature values and write compensation data into the control chip, and the control chip performs temperature compensation and zero point compensation on the sensor by analyzing digital signal compensation values at various temperatures written into the EEPROM of the control chip.
Description
Technical Field
The invention relates to the technical field of ammeter manufacturing, in particular to a temperature compensation structure of a direct current sensor.
Background
In the practical application process of the current sensor, along with the change of the environmental temperature, the measurement result of the sensor can be influenced by different degrees, so that the research and development and the application of some sensors with high precision and high stability are difficult, particularly when the sensor is used as a metering component in a direct current electric energy meter, the working temperature requirement of the electric energy meter from minus 40 ℃ to 85 ℃ is received, the span of a temperature interval is large, and the change of the output of the sensor caused by the temperature rise or fall can exceed the requirement of the metering precision of the electric energy meter. On the other hand, the zero output of the sensor is also an important factor influencing the accuracy of the sensor;
the current sensor calibration mode mostly adopts a coarse adjustment mode and a fine adjustment mode of two potentiometers, and the mode is limited by the precision of the potentiometers, has insufficient compensation precision and is not suitable for long-time use; the other mode is that when the sensor components are selected, the components with better temperature coefficients are selected more, the influence of temperature on the test result is reduced from the source aspect, the effect is obvious, but the cost of the sensor is greatly increased, and the sensor is not suitable for batch application.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a temperature compensation structure of a direct current sensor, which adopts a singlechip to control a compensation circuit and can calibrate the output under different temperatures while compensating the zero point output.
The technical scheme of the invention is as follows: a temperature compensation structure of a direct current sensor comprises an electromagnetic induction module, a control chip, a temperature sensor sampling circuit, a control chip auxiliary circuit and an output compensation circuit, wherein the electromagnetic induction module comprises a circular magnetic core with a notch, a coil is wound on the surface of the magnetic core, the coil is provided with a first coil interface and a second coil interface, the first coil interface and the second coil interface are respectively connected to the control chip auxiliary circuit, a square magnetic sensor with two output ports is placed at the notch, and the magnetic sensor is connected with two ends of an operational amplifier through the output ports; the temperature sensor sampling circuit comprises a temperature-sensitive resistor and a divider resistor, wherein one end of the temperature-sensitive resistor is grounded, the other end of the temperature-sensitive resistor is connected with the control chip, one end of the divider resistor is connected with a power supply, and the other end of the divider resistor is connected with the control chip; the control chip auxiliary circuit is connected to the control chip through a signal wire, two interfaces are arranged on the control chip, the interfaces are respectively connected with a power supply and a ground, and the control chip further comprises a serial port and two external communication interfaces; the control chip is connected with an external device through two external communication interfaces, the control chip is connected with a digital potentiometer through a signal line, the communication protocol of the control chip and the digital potentiometer is I2C protocol, a protocol variable and a temperature variable are arranged in 12C protocol, a temperature-sensitive resistor is arranged in an auxiliary circuit of the control chip, and the temperature and the amplitude sensed by the temperature-sensitive resistor are in calibration function communication with the control chip through a UART communication mode;
the output compensation circuit comprises an operational amplifier, a first resistor and a second resistor, wherein the operational amplifier is provided with a reverse input end, a same-direction input end and an output end, the reverse input end and the same-direction input end are sequentially connected with two internal ports of the magnetic sensor through the first resistor and the second resistor respectively, the output end is connected with the control chip auxiliary circuit, and the output end of the magnetic sensor connected with the same-direction input end is connected with the control chip through the control chip auxiliary circuit;
preferably, the control chip adopts an MS83F0802B chip, and the control chip 10 is provided with an Eeprom chip and an RAM chip;
preferably, the temperature-sensitive resistor adopts NTC3470K, and the voltage-dividing resistor adopts MCP 4017;
the software structure comprises: and a digital potentiometer assignment module.
The digital potentiometer assignment module comprises a potentiometer, an I2C _ SCL value and an I2C _ SDA value, and the steps of the digital potentiometer assignment module are as follows:
the first step is as follows: setting initial values of the I2C _ SCL value and the I2C _ SDA value, judging whether the I2C _ SCL value is equal to 0, if so, delaying to read, overlapping the I2C values, sending the set initial values of the I2C _ SCL value and the I2C _ SDA value, and turning to a third step; otherwise, delaying reading and turning to the second step;
the second step is that: judging whether the initial values of the I2C _ SCL value and the I2C _ SDA value are equal to 0 or not, if both are equal to 0, reading parameters from the potentiometer, and turning to the third step; otherwise, assigning the value of the I2C _ SCL to be equal to 1, and turning to the third step;
the third step: setting the I2C _ SDA value equal to 1;
the fourth step: and (6) ending.
The invention has the beneficial effects that:
1) the invention provides working frequency and other necessary working conditions for the control chip through the auxiliary circuit of the control chip;
2) the external communication interface can be connected with a computer serial port, and compensation values at different temperatures are written into an EEPROM (electrically erasable programmable read-only memory) of a control chip by using a computer, so that the purposes of power-off storage and work when power is on are achieved;
3) the external communication interface connects an external communication circuit to the control chip, can read the temperature value and write compensation data into the control chip;
4) the control chip of the invention carries out temperature compensation and zero point compensation on the sensor by analyzing the digital signal compensation value at each temperature written in the EEPROM of the control chip.
Description of the drawings:
FIG. 1 is a schematic diagram of the main structure of the present invention;
FIG. 2 is a functional diagram of data processing of the control chip;
FIG. 3 is a control logic diagram of the main program;
FIG. 4 is a block diagram of a digital potentiometer assignment;
FIG. 5 is a block diagram of an ADC sampling routine;
in the figure, 1, coil; 2. a magnetic core; 3. a magnetic sensor; 4. a first resistor; 5. a second resistor; 6. an operational amplifier; 7. a temperature-sensitive resistor; 8. a voltage dividing resistor; 9. a control chip auxiliary circuit; 10. a control chip; 11. and a second external communication interface. 12. A first coil interface; 13. an output interface of the operational amplifier; 14. a second coil interface; 15. connecting a power supply interface; 16. and a first external communication interface.
The specific implementation mode is as follows:
as shown in fig. 1 to 5, the related hardware structure includes an electromagnetic induction module, a control chip 10, a temperature sensor sampling circuit, a control chip auxiliary circuit 9, and an output compensation circuit. The electromagnetic induction module contains a circular magnetic core 2 that has a breach, 2 surperficial coiling coils 3 of magnetic core, coil 3 be equipped with coil interface one 12 and coil interface two 14, the coil interface one 12 that is tied and coil interface two 14 are connected to control chip auxiliary circuit 9, receive control chip auxiliary circuit as electromagnetic induction's feedback signal after 3 both ends of coil are drawn forth the breach department place a square and have the magnetic sensor 3 of two delivery outlets, magnetic sensor 3 pass through the delivery outlet with operational amplifier 6 link to each other. A current-carrying wire penetrates through the magnetic core 2 and generates a magnetic field at a notch of the magnetic core 2, the magnetic sensor 3 converts a magnetic field signal into a pair of differential signals, and the differential signals are led out through two output ends of the magnetic sensor, and it is assumed that an output voltage value V1 of the magnetic sensor connected with a reverse input port and an output voltage value V2 connected with a same-direction input port in the graph 1 are respectively connected to an input end of an operational amplifier 6 through a first current-reducing resistor 4 and a second resistor 5; in practical situations, due to manufacturing processes and technologies, the differential output of the magnetic sensor 3 is not equal, and the difference between different products is large, and in combination with the change of temperature, the magnetic sensor 3 outputs an error result under the condition of no magnetic field or high and low temperature operation, which requires directional compensation of the output of the magnetic sensor 3.
The temperature sensor sampling circuit comprises a temperature-sensitive resistor 7 and a divider resistor 8, one end of the divider resistor 8 is grounded, the other end of the divider resistor is connected with a control chip 10, one end of the temperature-sensitive resistor 7 is connected with a power supply, and one end of the temperature-sensitive resistor is connected with a pin 2 of the control chip 10; along with the change of the temperature, the voltage on the pin 2 corresponds to the changed resistance value of the temperature-sensitive resistor 7 one by one, and the control chip 10 converts the temperature value into a digital signal through an internal digital-to-analog conversion module, processes and stores the digital signal into an EEPROM (electrically erasable programmable read-only memory); at this time, digital signals are transmitted to pins 7 and 8 of the control chip through the first external communication interface and the 11 external communication interface, the control chip outputs a corresponding voltage V3 on pin 1, and the adjustment is carried out so that V3+ V2= V1; the control chip auxiliary circuit 9 is connected to the pin 3 and the pin 4 of the control chip 10, and provides working frequency and other necessary working conditions for the control chip; the VCC end on the control chip 10 is connected with the GND end of the power supply and is grounded, the pin 7 and the pin 8 of the control chip 10 are respectively connected with the first external communication interface 16 and the second external communication interface 11, and after the external communication circuit is connected to the control chip 10, the external communication circuit can read a temperature value and write compensation data into the external communication interface, and the external communication circuit is analyzed by the control chip 10 and then transmitted to the output end of the external communication interface;
the output compensation circuit comprises an operational amplifier 6, a first resistor 4 and a second resistor 5, wherein the reverse input end of the operational amplifier 6 is connected with the first resistor 4, the equidirectional input end of the operational amplifier is connected with the second resistor 5 and is connected with two ports of the magnetic sensor 3, an output port 13 is connected to an auxiliary circuit 9 of the control chip, a pin 1 of the control chip 10 is connected with one end of the output signals at two ends of the magnetic sensor 3, the port is connected with the equidirectional input end of the operational amplifier 6, the voltages of the two output pins of the magnetic sensor are equal when the magnetic field is zero through the change of the output bias voltage of the control chip 10, and further, after the result is realized, the signal of the differential signal output by the magnetic sensor after being amplified by the operational amplifier is zero or approaches to zero.
Preferably, the control chip adopts an MS83F0802B chip, and is provided with an eeprom chip and an RAM chip;
preferably, the temperature-sensitive resistor adopts NTC3470K, and the voltage-dividing resistor adopts MCP 4017;
the software structure comprises: ADC sampling program module, digital potentiometer assignment module, ADC sampling program module contains temperature calibration module and ADC acquisition function, temperature calibration module includes temperature calibration point value, serial ports debugging flag bit, PWM numerical value, I2C numerical value, ADC acquisition function is equipped with temperature matrix [ n ] and calibration value, the calibration value includes AD sampling value, NTC voltage numerical value, NTC temperature value, and n is the positive integer.
The invention communicates with the outside in a UART communication mode, and the external equipment operates the control chip by generating different instructions. Serial port communication setting: the baud rate is set to 9600bps, the even parity bit is set, and the stop bit is set to 1.
The digital potentiometer assignment module is shown in fig. 4, and includes a potentiometer, an I2C _ SCL value, and an I2C _ SDA value, and the steps of the digital potentiometer assignment module are as follows:
the first step is as follows: setting initial values of the I2C _ SCL value and the I2C _ SDA value, judging whether the I2C _ SCL value is equal to 0, if so, delaying to read, overlapping the I2C values, sending the set initial values of the I2C _ SCL value and the I2C _ SDA value, and turning to a third step; otherwise, delaying reading and turning to the second step;
the second step is that: judging whether the initial values of the I2C _ SCL value and the I2C _ SDA value are equal to 0 or not, if both are equal to 0, reading parameters from the potentiometer, and turning to the third step; otherwise, assigning the value of the I2C _ SCL to be equal to 1, and turning to the third step;
the third step: setting the I2C _ SDA value equal to 1;
the fourth step: and (6) ending.
The circuit of the invention identifies the temperature through the sampling circuit and generates different outputs to each temperature point through the singlechip, thereby achieving the purpose of temperature change compensation and zero point compensation of the sensor by the circuit.
Claims (6)
1. A temperature compensation structure of a direct current sensor is characterized in that: the electromagnetic induction module comprises a circular magnetic core with a gap, a coil is wound around the surface of the magnetic core, the coil is provided with a first coil interface and a second coil interface, the first coil interface and the second coil interface are respectively connected to the auxiliary circuit of the control chip, a square magnetic sensor with two output ports is placed at the gap, and the magnetic sensor is connected with the two ends of an operational amplifier through the output ports; the temperature sensor sampling circuit comprises a temperature-sensitive resistor and a divider resistor, wherein one end of the temperature-sensitive resistor is grounded, the other end of the temperature-sensitive resistor is connected with the control chip, one end of the divider resistor is connected with a power supply, and the other end of the divider resistor is connected with the control chip; the control chip auxiliary circuit is connected to the control chip through a signal wire, two interfaces are arranged on the control chip, the interfaces are respectively connected with a power supply and a ground, and the control chip further comprises a serial port and two external communication interfaces; the control chip is connected with an external device through two external communication interfaces, the control chip is connected with a digital potentiometer through a signal line, the communication protocol of the control chip and the digital potentiometer is I2C protocol, a protocol variable and a temperature variable are arranged in 12C protocol, a temperature-sensitive resistor is arranged in an auxiliary circuit of the control chip, and the temperature and the amplitude sensed by the temperature-sensitive resistor are in calibration function communication with the control chip through a UART communication mode; the output compensation circuit contain operational amplifier, resistance one, resistance two, operational amplifier is equipped with reverse input end, syntropy input and output port, reverse input end with syntropy input respectively through resistance one, resistance two in proper order with two inside ports of magnetic sensor link to each other, output port connects control chip auxiliary circuit, with syntropy input end is connected the output of magnetic sensor passes through control chip auxiliary circuit links to each other with control chip.
2. The direct current sensor temperature compensation structure of claim 1, wherein: the control chip adopts an MS83F0802B chip, and is provided with an Eeprom chip and an RAM chip.
3. The direct current sensor temperature compensation structure of claim 1, wherein: the temperature-sensitive resistor adopts NTC3470K, and the voltage-dividing resistor adopts MCP 4017.
4. The direct current sensor temperature compensation structure of claim 2, wherein: the software structure comprises a digital potentiometer assignment module.
5. The direct current sensor temperature compensation structure of claim 4, wherein: the control chip communicates with external equipment in a UART communication mode, and the external equipment operates the control chip by generating different instructions.
6. Serial port communication setting: setting a baud rate of 19200bps, setting an even check bit and setting a stop bit 1;
the temperature compensation structure of a DC current sensor according to claim 4, wherein said digital potentiometer assignment module comprises a potentiometer, I2C _ SCL value, I2C _ SDA value, said digital potentiometer assignment module comprises the steps of:
the first step is as follows: setting initial values of the I2C _ SCL value and the I2C _ SDA value, judging whether the I2C _ SCL value is equal to 0, if so, delaying to read, overlapping the I2C values, sending the set initial values of the I2C _ SCL value and the I2C _ SDA value, and turning to a third step; otherwise, delaying reading and turning to the second step;
the second step is that: judging whether the initial values of the I2C _ SCL value and the I2C _ SDA value are equal to 0 or not, if both are equal to 0, reading parameters from the potentiometer, and turning to the third step; otherwise, assigning the value of the I2C _ SCL to be equal to 1, and turning to the third step;
the third step: setting the I2C _ SDA value equal to 1;
the fourth step: and (6) ending.
Priority Applications (1)
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| CN202111557635.8A CN114296019A (en) | 2021-12-19 | 2021-12-19 | Temperature compensation structure of direct current sensor |
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| CN202111557635.8A CN114296019A (en) | 2021-12-19 | 2021-12-19 | Temperature compensation structure of direct current sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114994382A (en) * | 2022-07-14 | 2022-09-02 | 北京智芯半导体科技有限公司 | Temperature compensation method and device for electric energy metering, electric energy metering device and medium |
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