CN111323632A - AC/DC zero-flux fluxgate current sensor and program control configuration and calibration method thereof - Google Patents

Abstract

The invention discloses an alternating current-direct current zero-flux fluxgate current sensor, which comprises a fluxgate current sensor body and a configuration and calibration circuit for configuring and calibrating the fluxgate current sensor body, wherein the fluxgate current sensor body comprises a first iron core, a second iron core, an excitation winding, a feedback winding and a measurement winding; the configuration and calibration circuit comprises a processor, a crystal oscillator, an RS232 interface circuit, an excitation source amplification driving circuit, a programmable compensation signal tracker, a programmable filter, a phase-sensitive demodulation circuit, a PI control circuit and a power amplifier; the invention discloses a program control configuration and calibration method of an AC/DC zero-flux fluxgate current sensor. The invention can automatically match the offset current caused by the inconsistency of the parameters of the two iron cores, greatly reduce the requirement on the process consistency of the two fluxgate iron cores, realize the optimal performance of the fluxgate sensor, and has strong practicability and high popularization and use values.

Description

AC and DC zero-flux fluxgate current sensor and its program-controlled configuration and calibration method

technical field

The invention belongs to the technical field of intelligent sensors, and in particular relates to an AC and DC zero-flux gate current sensor and a program-controlled configuration and calibration method thereof.

Background technique

Fluxgate current sensors play an important role in the field of high-performance current measurement because of their fast response time, good temperature characteristics, and high sensitivity. However, the fluxgate current sensor has high requirements on the consistency of the iron core material and manufacturing process, and the two iron cores and windings of the fluxgate require the same parameters, resulting in high cost, complicated process, difficult debugging, and some problems. The offset voltage and offset current of the source electronic components will also cause the secondary current of the fluxgate to have an offset current output.

The excitation signal of the fluxgate sensor has a great influence on the entire system of the fluxgate. Generally, the selection of the excitation signal is considered from the aspects of signal frequency stability, signal amplitude stability, phase stability and waveform stability. . In particular, the frequency of the excitation signal greatly affects the working performance of the sensor. If the frequency is too high, the noise will increase; if the frequency is too low, the sensitivity of the sensor will be reduced. The frequency is fixed between a few hundred and several kilohertz, and the bandpass frequency of the second harmonic filter cannot be changed.

At present, the typical foreign IT series AC and DC fluxgate current sensors are from Lem Electronics (LEM), and there are Shenzhen Hangzhi Precision IIT series AC and DC fluxgate current sensors in China. These companies produce and develop AC and DC fluxgate current sensors based on the principle of fluxgate. The sensor can achieve ppm-level linearity, but due to the high requirements for the parameters such as the iron core and winding of the fluxgate, the complex process of the iron core, the high cost, and the inability to calibrate the zero offset by means of digital program control technology, etc., the current 60A to 2000A The price of the fluxgate current sensor is between several thousand yuan and tens of thousands of yuan, which greatly limits its application range, and there are also the following defects:

(1) The iron core material and process requirements are high, and the cost is expensive;

(2) For different applications, the best application effect cannot be achieved by configuring the parameters of the current transformer;

(3) Factory calibration is not available for inherent zero offset current.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an AC and DC zero-flux fluxgate current sensor, which is novel and reasonable in design, and can greatly reduce the process consistency of the two fluxgate iron cores. It can achieve the best performance of the fluxgate sensor, has strong practicability, and has high promotion and use value.

In order to solve the above technical problems, the technical solution adopted in the present invention is: an AC and DC zero-flux fluxgate current sensor, comprising a configuration and calibration circuit for configuring and calibrating the fluxgate current sensor body, the configuration And the calibration circuit includes a processor and an excitation source amplifying drive circuit that is connected to the processor and used to provide excitation voltage for the excitation winding of the fluxgate current sensor body, and is used to compensate the second iron core in the fluxgate current sensor body. A programmable compensation signal tracker that is inconsistent with the excitation magnetic field caused by the material and manufacturing process of the first iron core, and a compensation current output circuit for outputting compensation current to the feedback winding in the fluxgate current sensor body, the magnetic flux The excitation winding in the gate current sensor body is connected with the output end of the excitation source amplifier drive circuit, the excitation winding in the fluxgate current sensor body is connected with the output end of the programmable compensation signal tracker, and the input end of the compensation current output circuit It is connected with the measurement winding, and the feedback winding is connected with the output end of the compensation current output circuit.

For the above-mentioned AC-DC zero-flux fluxgate current sensor, the processor is a DSP digital signal processor, the clock input interface of the DSP digital signal processor is connected with a crystal oscillator, the excitation source amplifies the drive circuit and the programmable compensation The signal trackers are all connected with the timer Timer1 of the DSP digital signal processor, the timer Timer1 of the DSP digital signal processor is also connected with a frequency multiplier circuit, and the serial port RS232 of the DSP digital signal processor is connected with an RS232 interface circuit, the programmable compensation signal tracker is connected with the first SPI interface SPI1 of the DSP digital signal processor, and the compensation current output circuit includes a programmable filter ( 5), and the phase-sensitive demodulation circuit (6), the PI control circuit (7) and the power amplifier (8) connected to the output end of the programmable filter (5) in turn, the phase-sensitive demodulation circuit (6) and the multiplier The output terminal of the frequency circuit (4) is connected.

引脚连接，所述74HC74芯片的Q引脚为倍频电路的输出端。In the above-mentioned AC/DC zero-flux gate current sensor, the frequency multiplier circuit includes a 74HC74 chip, the CP pin of the 74HC74 chip is connected with the timer Timerl of the DSP digital signal processor, and the D pin of the 74HC74 chip is connected. and

Pin connection, the Q pin of the 74HC74 chip is the output end of the frequency multiplier circuit.

For the above-mentioned AC/DC zero-flux fluxgate current sensor, the programmable filter includes an active filter chip UAF42, a DA conversion chip U1 and a DA conversion chip U2 whose model is AD5545, and an operational amplifier chip whose model is AD8620 U3 and op amp chip U4, as well as resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6 and resistor R7, the SPI interface of the DA conversion chip U1 and the SPI interface of the DA conversion chip U2 are all the same as the DSP digital The second SPI interface SPI2 of the signal processor is connected, the VREF interface of the DA conversion chip U1 is connected to the 13th pin of the active filter chip UAF42, and is connected to the 5th pin of the active filter chip UAF42 through the resistor R3 Connect, the VREF interface of described DA conversion chip U2 is connected with the 7th pin of active filter chip UAF42, and is connected with the 12th pin of active filter chip UAF42 through resistance R6; The inverting signal input terminal is connected with the output terminal of the DA conversion chip U1, the in-phase signal input terminal of the operational amplifier chip U3 is grounded, and the output terminal of the operational amplifier chip U3 is connected with the RTB pin of the DA conversion chip U1, and It is connected with the 8th pin of the active filter chip UAF42 through the resistor R1; the inverting signal input end of the operational amplifier chip U4 is connected with the output end of the DA conversion chip U2, and the in-phase signal input end of the operational amplifier chip U4 is input The terminal is grounded, and the output terminal of the operational amplifier chip U4 is connected to the RTB pin of the DA conversion chip U2, and is connected to the 14th pin of the active filter chip UAF42 through the resistor R2; the resistor R4 is connected to the active filter chip UAF42. Between the 1st pin and the 5th pin of the filter chip UAF42, the resistor R5 is connected between the 5th pin and the 6th pin of the active filter chip UAF42. The twelfth pin is connected to the positive output terminal M+ of the measuring winding through the resistor R7, the negative output terminal M- of the measuring winding is grounded, and the sixth pin of the active filter chip UAF42 is the output terminal of the programmable filter .

In the above-mentioned AC/DC zero-flux fluxgate current sensor, the phase-sensitive demodulation circuit includes a voltage tracker composed of an operational amplifier chip U5 of the model AD8620 and an inverter composed of the operational amplifier chip U6 of the model AD8620, A two-to-one multiplexer composed of a two-to-one multiplexer chip CD4051, as well as a resistor R11, a resistor R12, a resistor R13 and a capacitor C1; the inverting input terminal of the operational amplifier chip U5 is connected to one end of the resistor R11 And it is the input end of the phase-sensitive demodulation circuit, the non-inverting input end of the operational amplifier chip U5 is connected to the output end; the inverting input end of the operational amplifier chip U6 is connected to the other end of the resistor R11, and is connected with the resistor R2 through the resistor R2. The output terminal of the operational amplifier chip U6 is connected, and the non-inverting input terminal of the operational amplifier chip U6 is grounded; the first signal input terminal pin CH1 of the two-to-one multiplexer chip CD4051 is connected to the output terminal of the operational amplifier chip U5 connected, the second signal input pin CH0 of the two-to-one multiplexer chip CD4051 is connected to the output end of the operational amplifier chip U6, and the address strobe pin of the two-to-one multiplexer chip CD4051 Both B and address strobe pin C are grounded, the address strobe pin A of the two-to-one multiplexer chip CD4051 is connected to the output end of the frequency multiplier circuit, and one end of the resistor R13 is connected to the two-to-one multiplexer The signal output pin of the converter chip CD4051 is connected to the pin, and the other end of the resistor R13 is the output end of the phase-sensitive demodulation circuit and is grounded through the capacitor C1.

In the above-mentioned AC/DC zero-flux fluxgate current sensor, the PI control circuit includes an operational amplifier chip OP07D, a resistor R15, a resistor R16, a resistor R17 and a capacitor C2, and one end of the resistor R15 is the input end of the PI control circuit, The inverting input terminal of the operational amplifier chip OP07D is connected to the other end of the resistor R15, the non-inverting input terminal of the operational amplifier chip OP07D is grounded, and a resistor R16 is connected between the output terminal and the inverting input terminal of the operational amplifier chip OP07D. , and the parallel resistor R17 and capacitor C2, the output end of the operational amplifier chip OP07D is the output end of the PI control circuit.

In the above-mentioned AC and DC zero-flux gate current sensor, the power amplifier includes a power amplifier chip OPA548, a resistor R21, a resistor R22, a resistor R23, a resistor R24 and a resistor R25, and one end of the resistor R21 is the input end of the power amplifier , the inverting input terminal of the power amplifier chip OPA548 is connected to the other end of the resistor R21, the non-inverting input terminal of the power amplifier chip OPA548 is grounded through the resistor R23, and the inverting input terminal of the power amplifier chip OPA548 is connected to the output terminal. There is a resistor R22 indirectly, a resistor R24 is connected between the non-inverting input end and the output end of the power amplifier chip OPA548, the output end of the power amplifier chip OPA548 is connected to one end of the resistor R25, and the other end of the resistor R25 is the power amplifier 's output.

For the above-mentioned AC/DC zero-flux fluxgate current sensor, the programmable compensation signal tracker includes a DA conversion chip U7 whose model is AD5545, an operational amplifier chip U8 and an operational amplifier chip U9 whose model is AD8620, and resistors R31, Resistor R32 and resistor R33, the VREF pin of the DA conversion chip U7 is connected with the timer Timer1 of the DSP digital signal processor, and the SPI pin of the DA conversion chip U7 is connected with the first SPI interface SPI1 of the DSP digital signal processor connected, the inverting input terminal of the operational amplifier chip U8 is connected with the output terminal pin of the DA conversion chip U7, the non-inverting input terminal of the operational amplifier chip U8 is grounded, and the output terminal of the operational amplifier chip U8 is connected to the DA conversion chip. The RFB pin of U7 is connected to the inverting input terminal of the operational amplifier chip U9 through the resistor R31, and the inverting input terminal of the operational amplifier chip U9 is connected to the VREF pin of the DA conversion chip U7 through the resistor R32. A resistor R33 is connected between the inverting input terminal and the output terminal of the operational amplifier chip U9. The non-inverting input terminal of the operational amplifier chip U9 is grounded and is the negative output terminal Vs- of the compensation current of the programmable compensation signal tracker. The output end of the chip U9 is the compensation current positive output end Vs+ of the programmable compensation signal tracker.

In the above-mentioned AC/DC zero-flux fluxgate current sensor, the excitation source amplifying drive circuit includes a power amplifier chip U10 and a power amplifier chip U11 whose models are OPA548, and a resistor R41 and a resistor R42; The inverting input terminal is connected to one end of the resistor R41 and is the input terminal of the excitation source amplifying drive circuit, and is connected to the timer Timer1 of the DSP digital signal processor. The non-inverting input terminal of the power amplifier chip U10 is connected to the output terminal, so the The inverting input terminal of the power amplifier chip U11 is connected to the other end of the resistor R41, the non-inverting input terminal of the power amplifier chip U11 is grounded, and a resistor R42 is connected between the inverting input terminal and the output terminal of the power amplifier chip U11, The output terminal of the power amplifier chip U10 is the voltage positive output terminal of the excitation source amplifying drive circuit, and the output terminal of the power amplifier chip U11 is the voltage negative output terminal of the excitation source amplifier driving circuit.

The invention also provides a method with simple steps and convenient implementation, which realizes the dynamic or static change of the excitation current frequency through the programmable timer, and realizes the dynamic or static change of the center frequency of the filter through the DA converter combined with the programmable filter. The static modification can realize different applications of the fluxgate and change its excitation frequency dynamically or statically for the iron core, which can achieve the best performance of the fluxgate sensor, has strong practicability, and promotes the use of high-value AC and DC zero flux. A program-controlled configuration and calibration method for a fluxgate current sensor, the method comprising the following steps:

Step 1, the excitation source amplifying drive circuit outputs a voltage square wave signal under the control of the processor, and the first iron core and the second iron core are connected in series in opposite directions through the excitation winding;

Step 2, when the excitation magnetic fields of the first iron core and the second iron core are inconsistent, output the compensation excitation signal to the excitation winding of the fluxgate current sensor body through the programmable compensation signal tracker under the control of the processor;

Step 3: When the primary current I _p is not zero, the signal output of the measurement winding contains the second harmonic;

Step 4: Extract the second harmonic component through the compensation current output circuit, adjust the second harmonic component to DC output, and output a compensation current I _s to the excitation winding in the fluxgate current sensor body.

Compared with the prior art, the present invention has the following advantages:

1. In the AC-DC zero-flux gate current sensor of the present invention, a programmable compensation signal tracker is designed in the configuration and calibration circuit, and the reference voltage of the DA conversion chip of the current type output type can be a continuous voltage input characteristic, The reference voltage is directly connected to the signal square wave T1 input, and the synchronization of the T1 voltage is scaled down through DAC conversion. Since the T1 signal output is a unipolar signal, in order to realize the compensation direction of the iron core, the forward and reverse directions can be used. Through the circuit of unipolar conversion bipolar, two-way compensation is realized, static compensation for the inconsistency of the excitation magnetic field of the first iron core and the second iron core is realized, and the compensation for the inconsistency of the iron core and the design can theoretically be compensated to close to At 0, the offset current can be increased to 25ppm compared to 80ppm of LEM's IT200-S series, which reduces the material requirements for the first iron core and the second iron core, and changes the process consistency requirements for the iron core into a The calibration parameters stored in the DSP can greatly reduce the manufacturing process and cost of the iron core.

2. In the AC-DC zero-flux fluxgate current sensor of the present invention, a programmable excitation source amplifying drive circuit, a programmable filter and a phase demodulation circuit are designed in the configuration and calibration circuit to realize the programmable excitation power supply. Adjustment, can configure different excitation frequencies statically or dynamically according to different applications and materials, such as measuring very low frequency (<1Hz) or DC signals, can configure lower frequency excitation current, reduce noise, if the measurement frequency requires high or iron The core material can adapt to high-frequency signals, and can be configured with higher frequency excitation current to improve measurement bandwidth and sensitivity.

3. The present invention can realize the zero-position calibration of the AC and DC zero-flux gate current sensors through the RS232 communication port and calibration software before leaving the factory, and can also realize the calibration of the AC-DC zero-flux gate current sensor through the RS232 communication port and the calibration software during measurement or before leaving the factory. The excitation frequency and band-pass filter frequency of the DC zero-flux fluxgate current sensor are dynamically or statically modified by project detection, and the parameters of the iron core are optimally matched with practical applications. The invention can realize the design of 1000A-level AC and DC current sensors. .

4. For the fixed-mounted AC-DC zero-flux gate current sensor, the zero-position compensation calibration can be performed after the fixed position is installed, which can eliminate the influence of the geomagnetic field on the DC offset.

5. The present invention can realize the AC-DC zero-flux gate current sensor, and can achieve the best matching and application effect with the iron core by configuring the excitation frequency of the current transformer.

6. The present invention can realize the program-controlled configuration and calibration method of the AC-DC zero-flux fluxgate current sensor, the method steps are simple, and the realization is convenient, and the dynamic or static change of the excitation current frequency can be realized through the programmable timer, and the DA conversion can be performed. Combined with programmable filters, the filter can be dynamically or statically modified to realize the center frequency of the filter, thus realizing different applications of the fluxgate and changing its excitation frequency dynamically or statically for the iron core, which can achieve the best fluxgate sensor. High performance, strong practicability, and high promotion and use value.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the circuit principle block diagram of the AC and DC zero-flux fluxgate current sensor of the present invention;

Fig. 2 is the circuit schematic diagram of the frequency multiplication circuit of the present invention;

Fig. 3 is the circuit schematic diagram of the programmable filter of the present invention;

Fig. 4 is the circuit schematic diagram of the phase-sensitive demodulation circuit of the present invention;

Fig. 5 is the circuit schematic diagram of the PI control circuit of the present invention;

Fig. 6 is the circuit schematic diagram of the power amplifier of the present invention;

Fig. 7 is the circuit schematic diagram of the programmable compensation signal tracker of the present invention;

8 is a circuit schematic diagram of an excitation source amplifying drive circuit of the present invention;

FIG. 9 is a block diagram of the method of the program-controlled configuration and calibration method of the AC/DC zero-flux fluxgate current sensor according to the present invention.

Description of reference numbers:

1-processor; 2-crystal oscillator; 3-RS232 interface circuit;

4-frequency multiplier circuit; 5-programmable filter; 6-phase-sensitive demodulation circuit;

7-PI control circuit; 8-power amplifier; 9-first iron core;

10-Second iron core; 11-Programmable compensation signal tracker;

12- Excitation source amplifier drive circuit.

Detailed ways

As shown in FIG. 1 , the AC-DC zero-flux fluxgate current sensor of the present invention includes a configuration and calibration circuit for configuring and calibrating the fluxgate current sensor body, and the fluxgate current sensor body includes a first an iron core 9 and a second iron core 10, an excitation winding wound around the first iron core 9 and the second iron core 10, a feedback winding wound around the first iron core 9 and the second iron core 10, and a feedback winding wound around the first iron core 9 and the second iron core 10 Measurement windings on the first iron core 9 and the second iron core 10; the configuration and calibration circuit includes a processor 1 and an excitation voltage for the excitation winding of the fluxgate current sensor body, both connected to the processor 1 The excitation source amplification drive circuit 12, the programmable compensation signal tracker 11 for compensating for the inconsistent excitation magnetic field caused by the material and manufacturing process of the second iron core 10 and the first iron core 9 in the fluxgate current sensor body are inconsistent, and A compensation current output circuit for outputting compensation current to the feedback winding in the body of the fluxgate current sensor, the excitation winding in the body of the fluxgate current sensor is connected to the output end of the excitation source amplifying drive circuit 12, the fluxgate current The excitation winding in the sensor body is connected to the output end of the programmable compensation signal tracker 11 , the input end of the compensation current output circuit is connected to the measurement winding, and the feedback winding is connected to the output end of the compensation current output circuit.

During specific implementation, the first iron core 9 and the second iron core 10 are both made of permalloy.

In this embodiment, the processor 1 is a DSP digital signal processor having a clock input interface, a timer Timer1, a serial port RS232, a first SPI interface SPI1 and a second SPI interface SPI2, and the clock of the DSP digital signal processor The input interface is connected with a crystal oscillator 2, the excitation source amplifying drive circuit 12 and the programmable compensation signal tracker 11 are both connected with the timer Timer1 of the DSP digital signal processor, and the serial port RS232 of the DSP digital signal processor is connected with RS232 Interface circuit 3, the programmable compensation signal tracker 11 is connected with the first SPI interface SPI1 of the DSP digital signal processor, and the compensation current output circuit includes a programmable compensation current output circuit connected with the second SPI interface SPI2 of the DSP digital signal processor The filter 5, and the phase-sensitive demodulation circuit 6, the PI control circuit 7 and the power amplifier 8 sequentially connected to the output end of the programmable filter 5, the phase-sensitive demodulation circuit 6 is connected to the output end of the frequency multiplier circuit 4.

During specific implementation, the DSP digital signal processor is a DSP digital signal processor with a model of BF533 produced by Analog Devices. The output frequency of the DSP digital signal processor timer Timerl is T1=10MHz*D/2 ³² , where D is any integer from 1 to (2 ³² -1), that is, the timing T1 can output 0.00023Hz～10MHz frequency value in the range.

During specific implementation, the crystal oscillator 2 is an active crystal oscillator with 0.1 ppm and 10 MHz. The RS232 interface circuit 3 is an RS232 interface composed of a MAX232 interface conversion chip.

引脚连接，所述74HC74芯片的Q引脚为倍频电路4的输出端。即所述倍频电路4由D型上升沿触发器实现。In this embodiment, as shown in FIG. 2 , the frequency multiplier circuit 4 includes a 74HC74 chip, the CP pin of the 74HC74 chip is connected to the timer Timer1 of the DSP digital signal processor, and the D pin of the 74HC74 chip is connected to

Pin connection, the Q pin of the 74HC74 chip is the output end of the frequency multiplier circuit 4. That is, the frequency multiplier circuit 4 is realized by a D-type rising edge flip-flop.

In this embodiment, as shown in FIG. 3 , the programmable filter 5 includes an active filter chip UAF42, a DA conversion chip U1 and a DA conversion chip U2 whose model is AD5545, and an operational amplifier chip U3 whose model is AD8620 and operational amplifier chip U4, as well as resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6 and resistor R7, the SPI interface of the DA conversion chip U1 and the SPI interface of the DA conversion chip U2 are all connected with the DSP digital signal The second SPI interface SPI2 of the processor is connected, the VREF interface of the DA conversion chip U1 is connected with the 13th pin of the active filter chip UAF42, and is connected with the 5th pin of the active filter chip UAF42 through the resistor R3 , the VREF interface of the DA conversion chip U2 is connected with the 7th pin of the active filter chip UAF42, and is connected with the 12th pin of the active filter chip UAF42 through the resistor R6; The phase signal input terminal is connected with the output terminal of the DA conversion chip U1, the in-phase signal input terminal of the operational amplifier chip U3 is grounded, and the output terminal of the operational amplifier chip U3 is connected with the RTB pin of the DA conversion chip U1, and is passed through The resistor R1 is connected with the 8th pin of the active filter chip UAF42; the inverting signal input end of the operational amplifier chip U4 is connected with the output end of the DA conversion chip U2, and the in-phase signal input end of the operational amplifier chip U4 is connected Grounding, the output end of the operational amplifier chip U4 is connected to the RTB pin of the DA conversion chip U2, and is connected to the 14th pin of the active filter chip UAF42 through the resistor R2; the resistor R4 is connected to the active filter Between the 1st pin and the 5th pin of the chip UAF42, the resistor R5 is connected between the 5th pin and the 6th pin of the active filter chip UAF42, and the first pin of the active filter chip UAF42 is connected. The 12th pin is connected to the positive output terminal M+ of the measurement winding through the resistor R7, the negative output terminal M- of the measurement winding is grounded, and the 6th pin of the active filter chip UAF42 is the output terminal of the programmable filter 5 .

The active filter chip UAF42 is a general-purpose active filter module developed by TI. It is a general-purpose second-order filter component. It can have high-pass, low-pass, and band-pass outputs at the same time. In this embodiment, only UAF42 is used. In order to achieve the function of configurable band-pass frequency, the present invention adds a DA conversion chip U1 and a DA conversion chip U2, both of which are AD5545, and an operational amplifier chip U3 and an operational amplifier chip U4, both of which are AD8620. Two DA loops are constructed to configure different center frequency filters according to different excitation frequencies. The working process of the programmable filter 5 is as follows: the DA conversion chip U1 and the DA conversion chip U2 whose models are both AD5545 receive the command sent by the second SPI interface SPI2 of the DSP digital signal processor through the SPI interface, and output the corresponding voltage. value, thereby changing the bandpass center frequency of the active filter chip UAF42. The DA conversion chip U1 and the DA conversion chip U2 of the model AD5545 are 16Bit DAC chips, set the set value to D', and the center frequency of the band pass is (D'/2 ¹⁶ )/(2*pi*10 ^{- 9} *R1)=(D'/2 ¹⁶ )/(2*3.1415926*10 ^-9 *2*10 ³ )=79577k*(D'/2 ¹⁶ ), the value of D is 0～65536; , so the center frequency of the bandpass is 0-79.5kHz.

In this embodiment, as shown in FIG. 4 , the phase-sensitive demodulation circuit 6 includes a voltage tracker composed of an operational amplifier chip U5 of the model AD8620 and an inverter composed of an operational amplifier chip U6 of the model AD8620. A two-to-one multiplexer composed of a two-to-one multiplexer chip CD4051, and a resistor R11, a resistor R12, a resistor R13 and a capacitor C1; the inverting input terminal of the operational amplifier chip U5 is connected to one end of the resistor R11 and It is the input end of the phase-sensitive demodulation circuit 6, and the non-inverting input end of the operational amplifier chip U5 is connected to the output end; the inverting input end of the operational amplifier chip U6 is connected to the other end of the resistor R11, and is connected to the resistance R11 through the resistance R2. The output terminal of the operational amplifier chip U6 is connected, and the non-inverting input terminal of the operational amplifier chip U6 is grounded; the first signal input terminal pin CH1 of the two-to-one multiplexer chip CD4051 is connected to the output terminal of the operational amplifier chip U5 connected, the second signal input pin CH0 of the two-to-one multiplexer chip CD4051 is connected to the output end of the operational amplifier chip U6, and the address strobe pin of the two-to-one multiplexer chip CD4051 Both B and the address strobe pin C are grounded, the address strobe pin A of the two-to-one multiplexer chip CD4051 is connected to the output end of the frequency multiplier circuit 4, and one end of the resistor R13 is connected to the two-to-one-multiple The signal output pin of the circuit converter chip CD4051 is connected to the pin, and the other end of the resistor R13 is the output end of the phase-sensitive demodulation circuit 6 and is grounded through the capacitor C1.

When the phase-sensitive demodulation circuit 6 is working, the square wave signal T2 output by the frequency multiplier circuit 4 is directly used as the input of the address strobe pin A of the two-to-one multiplexer chip CD4051, which defines the signal composed of the operational amplifier chip U5. The signal output by the voltage tracker is +V _bpass , and the signal output by the inverter composed of the op amp chip U6 is -V _bpass . Since the phases of the square wave signal T2 and V _bpass are completely synchronized, it is assumed that the upper half wave of V _bpass is positive value, so when the square wave signal T2 is the upper half wave, V _pm =+V _bpass is a positive value, when the square wave signal T2 is the lower half wave, V _pm =-V _bpass , the value of V _bpass in the lower half cycle is negative, The output of the inverter formed by the operational amplifier chip U6 -V _bpass is positive, assuming that the upper half wave of V _bpass is a negative value, so when T2 is the upper half wave, the output of the phase sensitive demodulation circuit 6 The output signal V _pm =+V _bpass is a negative value, when T2 is the lower half-wave, the output signal V _pm =-V _bpass of the output terminal of the phase-sensitive demodulation circuit 6, the value of V _bpass in the second half-cycle is positive, through the operational amplifier chip U6 The output of the formed inverter -V _bpass is a negative value, so through the synchronous switching of the multiplexer chip CD4051, the full-wave demodulation is realized. The resistor R3 and the capacitor C1 reduce the DC signal after the full-wave arrangement. pass filtering.

In this embodiment, as shown in FIG. 5 , the PI control circuit 7 includes an operational amplifier chip OP07D, a resistor R15, a resistor R16, a resistor R17 and a capacitor C2, and one end of the resistor R15 is the input end of the PI control circuit 7, The inverting input terminal of the operational amplifier chip OP07D is connected to the other end of the resistor R15, the non-inverting input terminal of the operational amplifier chip OP07D is grounded, and a resistor R16 is connected between the output terminal and the inverting input terminal of the operational amplifier chip OP07D. , and the parallel resistor R17 and capacitor C2 , the output end of the operational amplifier chip OP07D is the output end of the PI control circuit 7 .

The PI control circuit 7 is used for proportional adjustment and integral adjustment. The proportional link can respond to the deviation of the system proportionally. Once the system has deviation, the proportional link will immediately adjust to reduce the deviation; if the proportional coefficient is large, it can speed up the adjustment and reduce the Deviation; the integral link makes the system eliminate the steady-state error and improve the degree of indifference; if there is an error, the integral link is carried out until there is no difference, the integral adjustment stops, and the integral link outputs a constant value; the strength of the integral action depends on the integral constant, the integral The smaller the constant is, the stronger the integral action is; otherwise the integral action is weaker.

In this embodiment, as shown in FIG. 6 , the power amplifier 8 includes a power amplifier chip OPA548 , a resistor R21 , a resistor R22 , a resistor R23 , a resistor R24 and a resistor R25 , and one end of the resistor R21 is the input end of the power amplifier 8 , the inverting input terminal of the power amplifier chip OPA548 is connected to the other end of the resistor R21, the non-inverting input terminal of the power amplifier chip OPA548 is grounded through the resistor R23, and the inverting input terminal of the power amplifier chip OPA548 is connected to the output terminal. There is a resistor R22 indirectly, a resistor R24 is connected between the non-inverting input end and the output end of the power amplifier chip OPA548, the output end of the power amplifier chip OPA548 is connected to one end of the resistor R25, and the other end of the resistor R25 is the power amplifier 8 outputs.

The resistor R25 is a feedback resistor, and the power amplifier 8 can complete the proportional amplification of voltage to current; the output current of the power amplifier 8 I _pow =R22*V _pi /(R21*R25)=1k*V _pi / (10K*0.1)= _Vpi /1.

In this embodiment, as shown in FIG. 7 , the programmable compensation signal tracker 11 includes a DA conversion chip U7 whose model is AD5545, an operational amplifier chip U8 and an operational amplifier chip U9 whose model is AD8620, and a resistor R31, a resistor R32 and resistor R33, the VREF pin of the DA conversion chip U7 is connected with the timer Timer1 of the DSP digital signal processor, the SPI pin of the DA conversion chip U7 is connected with the first SPI interface SPI1 of the DSP digital signal processor , the inverting input terminal of the operational amplifier chip U8 is connected with the output terminal pin of the DA conversion chip U7, the non-inverting input terminal of the operational amplifier chip U8 is grounded, and the output terminal of the operational amplifier chip U8 is connected to the DA conversion chip U7 The RFB pin is connected, and is connected with the inverting input terminal of the operational amplifier chip U9 through the resistance R31, and the inverting input terminal of the operational amplifier chip U9 is connected with the VREF pin of the DA conversion chip U7 through the resistance R32. A resistor R33 is connected between the inverting input terminal and the output terminal of the amplifier chip U9. The non-inverting input terminal of the operational amplifier chip U9 is grounded and is the compensation current negative output terminal Vs- of the programmable compensation signal tracker 11. The operational amplifier The output end of the chip U9 is the compensation current positive output end Vs+ of the programmable compensation signal tracker 11 .

The programmable compensation signal tracker 11 is a unipolar to bipolar output circuit, and receives the set value D from the DSP digital signal processor through the SPI interface, Vs=D/32768-1*T1; D is 16Bit The value of the unsigned value is 0 to 65535, so the range of Vs is -T1 to T1, which completes the digital programmable output of T1, and converts unipolar to bipolar.

In this embodiment, as shown in FIG. 8 , the excitation source amplifying and driving circuit 12 includes a power amplifier chip U10 and a power amplifier chip U11 whose models are OPA548, and a resistor R41 and a resistor R42; the reverse of the power amplifier chip U10 The phase input terminal is connected to one end of the resistor R41 and is the input terminal of the excitation source amplifying drive circuit 12, and is connected to the timer Timer1 of the DSP digital signal processor. The non-phase input terminal of the power amplifier chip U10 is connected to the output terminal, so The inverting input terminal of the power amplifier chip U11 is connected to the other end of the resistor R41, the non-inverting input terminal of the power amplifier chip U11 is grounded, and a resistor R42 is connected between the inverting input terminal and the output terminal of the power amplifier chip U11, The output terminal of the power amplifier chip U10 is the voltage positive output terminal of the excitation source amplifier driving circuit 12 , and the output terminal of the power amplifier chip U11 is the voltage negative output terminal of the excitation source amplifier driving circuit 12 .

The power amplifier chip U10 constitutes a non-inverting amplifier, and the power amplifier chip U11 constitutes an inverting amplifier, so that the excitation source amplifying driving circuit 12 is a double-terminal driving output.

The program-controlled configuration and calibration method of the AC-DC zero-flux fluxgate current sensor of the present invention comprises the following steps:

Step 1, the excitation source amplifying drive circuit 12 outputs a voltage square wave signal under the control of the processor 1, and the first iron core 9 and the second iron core 10 are connected in series in the opposite direction through the excitation winding;

Step 2. When the excitation magnetic fields of the first iron core and the second iron core are inconsistent, the programmable compensation signal tracker is controlled by the processor to output the compensation excitation signal to the excitation winding of the fluxgate current sensor body to ensure the primary current. When I _p is 0, the measurement winding has no even harmonic components, that is, even harmonic components _Is = 0;

Step 3. When the primary current I _p is not zero, the signal output of the measurement winding contains the second harmonic and other even harmonics;

Step 4: Extract the second harmonic component through the compensation current output circuit, adjust the second harmonic component to DC output, and output a compensation current I _s to the excitation winding in the fluxgate current sensor body.

During specific implementation, the second harmonic component is extracted through the programmable filter 5; the second harmonic component is adjusted to a DC output through the phase-sensitive demodulation circuit 6; a compensation current is output through the PI control circuit 7 and the power amplifier 8 _Is ;

Under the control of the PI control circuit 7, the compensation current I _s is output to the excitation winding in the fluxgate current sensor body, and the dynamic balance is finally achieved, which is expressed as I _p *N ₁ =I _s *N ₂ , where N ₁ is the excitation The number of winding turns, N ₂ is the number of turns of the feedback winding.

To sum up, the present invention can automatically match the offset current caused by the inconsistent parameters of the two iron cores, can greatly reduce the requirements for the process consistency of the two fluxgate iron cores, and can realize the best performance of the fluxgate sensor. , can eliminate the influence of the earth's magnetic field on the DC offset, can improve the measurement bandwidth and sensitivity, has strong practicability, and has high promotion and use value.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications or equivalent replacements are made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. The utility model provides an alternating current-direct current zero flux fluxgate current sensor which characterized in that: the device comprises a configuration and calibration circuit for configuring and calibrating a fluxgate current sensor body, wherein the configuration and calibration circuit comprises a processor (1), an excitation source amplification driving circuit (12) which is connected with the processor (1) and used for providing excitation voltage for an excitation winding of the fluxgate current sensor body, a programmable compensation signal tracker (11) for compensating the inconsistency of excitation magnetic fields caused by the inconsistency of materials and manufacturing processes of a second iron core (10) and a first iron core (9) in the fluxgate current sensor body, and a compensation current output circuit for outputting compensation current to a feedback winding in the fluxgate current sensor body, the excitation winding in the fluxgate current sensor body is connected with the output end of the excitation source amplification driving circuit (12), the excitation winding in the fluxgate current sensor body is connected with the output end of the programmable compensation signal tracker (11), the input end of the compensation current output circuit is connected with the measuring winding, and the feedback winding is connected with the output end of the compensation current output circuit.

2. The ac/dc zero flux fluxgate current sensor according to claim 1, wherein: the processor (1) is a DSP digital signal processor, a clock input interface of the DSP digital signal processor is connected with a crystal oscillator (2), the excitation source amplification driving circuit (12) and the programmable compensation signal tracker (11) are both connected with a timer Timrl of the DSP digital signal processor, the timer Timrl of the DSP digital signal processor is also connected with a frequency doubling circuit (4), a serial port RS232 of the DSP digital signal processor is connected with an RS232 interface circuit (3), the programmable compensation signal tracker (11) is connected with a first SPI interface SPI1 of the DSP digital signal processor, the compensation current output circuit comprises a programmable filter (5) connected with a second SPI interface SPI2 of the DSP digital signal processor, and a phase sensitive demodulation circuit (6), a PI control circuit (7) and a power amplifier (8) which are sequentially connected with the output end of the programmable filter (5), and the phase-sensitive demodulation circuit (6) is connected with the output end of the frequency doubling circuit (4).

3. The ac/dc zero flux fluxgate current sensor according to claim 2, wherein: the frequency multiplier circuit (4) comprises a 74HC74 chip, a CP pin of the 74HC74 chip is connected with a timer Timel of a DSP digital signal processor, and a D pin of the 74HC74 chip is connected with a timer Timel

And the pin is connected, and the Q pin of the 74HC74 chip is the output end of the frequency doubling circuit (4).

4. The ac/dc zero flux fluxgate current sensor according to claim 2, wherein: the programmable filter (5) comprises an active filter chip UAF42, a DA conversion chip U1 and a DA conversion chip U2, the types of which are AD5545, an operational amplifier chip U3 and an operational amplifier chip U4, the types of which are AD8620, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6 and a resistor R7, wherein the SPI interface of the DA conversion chip U1 and the SPI interface of the DA conversion chip U2 are connected with a second SPI interface SPI2 of a DSP digital signal processor, the VREF interface of the DA conversion chip U1 is connected with a 13 th pin of the active filter chip UAF42 and is connected with a5 th pin of the active filter chip UAF42 through the resistor R3, the VREF interface of the DA conversion chip U2 is connected with a 7 th pin of the active filter chip UAF42 and is connected with a 12 th pin of the active filter chip UAF42 through the resistor R6; the inverting signal input end of the operational amplifier chip U3 is connected with the output end of a DA conversion chip U1, the non-inverting signal input end of the operational amplifier chip U3 is grounded, the output end of the operational amplifier chip U3 is connected with an RTB pin of the DA conversion chip U1, and is connected with the 8 th pin of an active filter chip UAF42 through a resistor R1; the inverting signal input end of the operational amplifier chip U4 is connected with the output end of a DA conversion chip U2, the non-inverting signal input end of the operational amplifier chip U4 is grounded, the output end of the operational amplifier chip U4 is connected with an RTB pin of the DA conversion chip U2 and is connected with a 14 th pin of an active filter chip UAF42 through a resistor R2; the resistance R4 connects between the 1 st pin and the 5 th pin of active filter chip UAF42, resistance R5 connects between the 5 th pin and the 6 th pin of active filter chip UAF42, the 12 th pin of active filter chip UAF42 is connected with the positive output end M + of measuring winding through resistance R7, the negative output end M-ground of measuring winding, the 6 th pin of active filter chip UAF42 is the output of programmable filter (5).

5. The ac/dc zero flux fluxgate current sensor according to claim 2, wherein: the phase-sensitive demodulation circuit (6) comprises a voltage tracker formed by an operational amplifier chip U5 with the model number of AD8620, an inverter formed by an operational amplifier chip U6 with the model number of AD8620, an alternative multiplexer formed by an alternative multiplexer chip CD4051, a resistor R11, a resistor R12, a resistor R13 and a capacitor C1; the inverting input end of the operational amplifier chip U5 is connected with one end of a resistor R11 and is the input end of a phase-sensitive demodulation circuit (6), and the non-inverting input end of the operational amplifier chip U5 is connected with the output end; the inverting input end of the operational amplifier chip U6 is connected with the other end of the resistor R11, and is connected with the output end of the operational amplifier chip U6 through a resistor R2, and the non-inverting input end of the operational amplifier chip U6 is grounded; a first signal input end pin CH1 of the one-of-two multiplexer chip CD4051 is connected with an output end of the operational amplifier chip U5, a second signal input end pin CH0 of the one-of-two multiplexer chip CD4051 is connected with an output end of the operational amplifier chip U6, an address gating pin B and an address gating pin C of the one-of-two multiplexer chip CD4051 are both grounded, an address gating pin A of the one-of-two multiplexer chip CD4051 is connected with an output end of the frequency doubling circuit (4), one end of a resistor R13 is connected with a signal output end pin of the one-of-two multiplexer chip CD4051, and the other end of the resistor R13 is an output end of the phase-sensitive demodulation circuit (6) and is grounded through a capacitor C1.

6. The ac/dc zero flux fluxgate current sensor according to claim 2, wherein: the PI control circuit (7) comprises an operational amplifier chip OP07D, a resistor R15, a resistor R16, a resistor R17 and a capacitor C2, one end of the resistor R15 is the input end of the PI control circuit (7), the inverting input end of the operational amplifier chip OP07D is connected with the other end of the resistor R15, the non-inverting input end of the operational amplifier chip OP07D is grounded, the resistor R16, the resistor R17 and the capacitor C2 are connected in parallel between the output end of the operational amplifier chip OP07D and the inverting input end, and the output end of the operational amplifier chip OP07D is the output end of the PI control circuit (7).

7. The ac/dc zero flux fluxgate current sensor according to claim 2, wherein: the power amplifier (8) comprises a power amplifier chip OPA548, a resistor R21, a resistor R22, a resistor R23, a resistor R24 and a resistor R25, one end of the resistor R21 is an input end of the power amplifier (8), an inverting input end of the power amplifier chip OPA548 is connected with the other end of the resistor R21, a non-inverting input end of the power amplifier chip OPA548 is grounded through the resistor R23, a resistor R22 is connected between the inverting input end and an output end of the power amplifier chip OPA548, a resistor R24 is connected between the non-inverting input end and the output end of the power amplifier chip OPA548, the output end of the power amplifier chip OPA548 is connected with one end of the resistor R25, and the other end of the resistor R25 is an output end of the power amplifier (8).

8. The ac/dc zero flux fluxgate current sensor according to claim 3, wherein: the programmable compensation signal tracker (11) comprises a DA conversion chip U7 with the model number AD5545, an operational amplifier chip U8 and an operational amplifier chip U9 with the model number AD8620, a resistor R31, a resistor R32 and a resistor R33, wherein a VREF pin of the DA conversion chip U7 is connected with a timer Timrl of a DSP digital signal processor, an SPI pin of the DA conversion chip U7 is connected with a first SPI interface SPI1 of the DSP digital signal processor, an inverting input end of the operational amplifier chip U8 is connected with an output end pin of the DA conversion chip U7, a non-inverting input end of the operational amplifier chip U8 is grounded, an output end of the operational amplifier chip U8 is connected with an RFB pin of the DA conversion chip U7 and is connected with an inverting input end of the operational amplifier chip U9 through a resistor R31, an inverting input end of the operational amplifier chip U9 is connected with a VREF pin of the DA conversion chip U7 through a resistor R32, and an inverting input end of the operational amplifier chip U36 33 is connected between the inverting input end of the operational amplifier chip U9 and the resistor, the non-inverting input end of the operational amplifier chip U9 is grounded and is a compensation current negative output end Vs + of the programmable compensation signal tracker (11), and the output end of the operational amplifier chip U9 is a compensation current positive output end Vs + of the programmable compensation signal tracker (11).

9. The ac/dc zero flux fluxgate current sensor according to claim 3, wherein: the excitation source amplification driving circuit (12) comprises a power amplifier chip U10 and a power amplifier chip U11 which are both OPA548, a resistor R41 and a resistor R42; the power amplifier circuit comprises a power amplifier chip U10, a resistor R41, a resistor R42, an excitation source amplification driving circuit (12), a timer Timrl of a DSP digital signal processor, a power amplifier chip U10, a resistor R11, a power amplifier chip U10, a resistor R11 and a power amplifier chip U11, wherein the reverse phase input end of the power amplifier chip U10 is connected with one end of the resistor R41 and is the input end of the excitation source amplification driving circuit (12), the non-phase input end of the power amplifier chip U11 is connected with the other end of the resistor R41, the non-phase input end of the power amplifier chip U11 is grounded, the resistor R42 is connected between the reverse phase input end and the output end of the power amplifier chip U11, the output.

10. A method of programming, configuring and calibrating a ac/dc fluxgate current sensor according to any of claims 1 to 9, the method comprising the steps of:

step one, an excitation source amplification driving circuit (12) outputs voltage square wave signals under the control of a processor (1), and the voltage square wave signals are connected in series on a first iron core (9) and a second iron core (10) in the opposite direction through excitation windings;

when the excitation magnetic fields of the first iron core and the second iron core are inconsistent, outputting a compensation excitation signal to an excitation winding of the fluxgate current sensor body through a programmable compensation signal tracker under the control of the processor (1);

step three, when the primary current I_pWhen the signal is not zero, the signal output of the measuring winding contains second harmonic;

step four, extracting the second harmonic component through the compensation current output circuit, adjusting the second harmonic component into direct current output, and outputting a compensation current I_sThe fluxgate current sensor body is energized with windings.

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