Detection circuit for high-precision fluxgate current sensor

Abstract

The utility model discloses a detection circuit used for a high-precision fluxgate current sensor. The detection circuit comprises a preceding stage detection loop connected in series with one side of an input end of the fluxgate current sensor; the rear-stage detection loop is connected in series with one side of the output end of the fluxgate current sensor; the front-stage detection loop is connected in series with a direct current source and a first shunt; the rear-stage detection loop is connected in series with a second shunt; the output positive electrode of the first shunt and the output positive electrode of the second shunt are in short circuit, and a voltmeter is arranged between the output negative electrode of the first shunt and the output negative electrode of the second shunt. The detection circuit for the high-precision fluxgate current sensor is low in cost, easy to implement and simple and convenient to operate, and the high-precision fluxgate current sensor can be detected by using the low-precision direct current source and the voltmeter, so that not only is the cost saved, but also the operation is simplified, and the test efficiency is improved.

Description

Technical Field

[0001] The utility model relates to a detection circuit, in particular to a detection circuit for a high-precision fluxgate current sensor. Background Art

[0002] The fluxgate technology is a technology widely used in the field of high-precision DC current sensors. Traditional fluxgate current sensors have extremely high precision, and can reach a measurement accuracy of 10 ppm (one in one hundred thousand). A current sensor cannot directly measure the magnitude of the current. It can only convert a large current into a proportional small current under isolated conditions. Therefore, the measurement of the accuracy of the current sensor is essentially the measurement of the accuracy and stability of this conversion coefficient. Of course, it is very convenient to indirectly measure the accuracy and stability of the conversion coefficient of the current sensor using a precision current source and a high-precision voltmeter. However, when measuring an ultra-high-precision current sensor, this method is very difficult to implement. Traditional testing and calibration methods face many challenges, such as the need for high-precision DC current sources and voltmeters, as well as a metrology room with constant temperature, constant humidity, and electromagnetic shielding. These devices are expensive and complex to operate, resulting in low testing efficiency and increased production costs. Content of the Utility Model

[0003] In order to solve the deficiencies of the above technologies, the utility model provides a detection circuit for a high-precision fluxgate current sensor.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is a detection circuit for a high-precision fluxgate current sensor, including:

[0005] A pre-stage detection circuit connected in series on one side of the input end of the fluxgate current sensor;

[0006] A post-stage detection circuit connected in series on one side of the output end of the fluxgate current sensor;

[0007] A DC current source and a first shunt are connected in series on the pre-stage detection circuit; a second shunt is connected in series on the post-stage detection circuit;

[0008] The positive poles of the outputs of the first shunt and the second shunt are short-circuited to each other, and a voltmeter is provided between the negative poles of the outputs of the first shunt and the second shunt.

[0009] Further, the pre-stage detection circuit is connected to the primary winding of the fluxgate current sensor.

[0010] Further, the post-stage detection circuit is connected to the compensation winding of the fluxgate current sensor.

[0011] A detection circuit for a high-precision fluxgate current sensor, including:

[0012] A pre-stage detection circuit connected in series on one side of the input end of the fluxgate current sensor;

[0013] A post-stage detection circuit connected in series on one side of the output end of the fluxgate current sensor;

[0014] A DC current source and a first shunt are connected in series on the pre-stage detection circuit; a second shunt is connected in series on the post-stage detection circuit;

[0015] The negative poles of the outputs of the first shunt and the second shunt are short-circuited to each other, and a voltmeter is provided between the positive poles of the outputs of the first shunt and the second shunt.

[0016] The utility model discloses a detection circuit for a high-precision fluxgate current sensor, which is a detection circuit with low cost, easy to implement and simple to operate. By using two shunts with the same precision level, a programmable DC current source and a digital voltmeter, the error of the sensor can be accurately determined by detecting the voltage difference between the shunt in the input circuit and the shunt in the output circuit. This method avoids the problem of using a high-precision DC current source and a high-precision digital voltmeter in the traditional test method. The detection of a high-precision fluxgate current sensor can be realized by using a low-precision DC current source and a voltmeter, which not only saves costs, but also simplifies the operation and improves the test efficiency. Brief Description of the Drawings

[0017] Figure 1 It is the electrical schematic diagram of the utility model.

[0018] Figure 2 It is the electrical schematic diagram of the fluxgate current sensor. Detailed Description of the Invention

[0019] The following further describes the utility model in detail with reference to the drawings and specific embodiments.

[0020] The detection circuit for a high-precision fluxgate current sensor provided by the utility model is a detection circuit for testing a high-precision fluxgate current sensor with low cost, easy to implement and simple to operate. First of all, the fluxgate current sensor is a technology that uses magnetic modulation technology to accurately convert a large current into a small current for measurement under isolated conditions. Compared with several other methods of isolated current measurement, its greatest advantage is high precision. As Figure 2As shown in the figure, there are three windings on a toroidal high-permeability iron core. Among them, the primary winding NP usually has only one turn and is the path for the measured current IP; the excitation winding N generates a symmetric alternating saturation magnetic flux in the toroidal high-permeability iron core; the compensation winding NS provides the compensation current IS. Its working principle is as follows: Assume that both the measured current IP and the compensation current IS are zero. There is only the magnetic flux generated by the excitation current in the toroidal high-permeability iron core, and there are no factors affecting the excitation magnetic flux. The voltage signal obtained after the symmetric square-wave voltage signal generating the excitation magnetic flux passes through the filter circuit is zero. If the measured current IP is not zero, the magnetic flux generated by the measured current IP destroys the symmetry of the excitation magnetic flux, that is, it destroys the symmetry of the excitation square wave. The asymmetric square-wave signal obtained after passing through the filter circuit is a non-zero voltage signal. This voltage signal is proportional to the measured current IP, and its positive and negative are related to the direction of the measured current IP. When the accuracy requirement is not high, this voltage signal can represent the measured current IP. To improve the detection accuracy, this voltage signal is used to control the current generator to generate the compensation current IS. The direction of the magnetic flux generated by the compensation current IS should be opposite to the direction of the magnetic flux generated by the measured current IP. The entire system forms a negative-feedback closed loop. In this way, the output of the active filter must be zero, and the magnitude of the compensation current IS conforms to the formula IS * NS = IP * NP. In fact, the magnetic fluxes generated by the two currents, namely the compensation current IS and the measured current IP, are equal in magnitude and opposite in direction and cancel each other out. According to the formula IS * NS = IP * NP, the value of the measured current IP can be obtained from the value of the compensation current IS; obviously, detecting zero is much easier and more accurate than directly measuring the magnitude of the current. Therefore, this method can achieve high-precision measurement of current; if one or two compensation magnetic rings and windings are added, ultra-high-precision measurement of current can also be achieved.

[0021] Combined with the working principle of the above fluxgate current sensor, the detection circuit for the high-precision fluxgate current sensor of the present utility model is set to include as Figure 1 shown:

[0022] A pre-stage detection circuit connected in series on one side of the input end of the fluxgate current sensor; and a post-stage detection circuit connected in series on one side of the output end of the fluxgate current sensor;

[0023] The pre-stage detection circuit is connected to the primary winding of the fluxgate current sensor.

[0024] The post-stage detection circuit is connected to the compensation winding of the fluxgate current sensor.

[0025] A DC current source DCA and a first shunt FLQ1 are connected in series on the pre-stage detection loop; a second shunt FLQ2 is connected in series on the post-stage detection loop; the DC current source DCA provides the current to be measured, and the first shunt FLQ1 is selected according to the transfer ratio and output range of the current sensor to be measured. In this embodiment, the fluxgate current sensor to be measured is 100A / 100mA, the output voltage range is ±4V, and the accuracy is 0.001%. The first shunt FLQ1 and the second shunt FLQ2 used are shunts with an accuracy of up to 1ppm. Since the output of this sensor is 4V when detecting the full scale of 100A, the parameters of the first shunt FLQ1 are 40mΩ / 100A / 4V, and the second shunt FLQ2 is 40Ω / 100mA / 4V.

[0026] When wiring, the positive poles of the output ends of the first shunt FLQ1 and the positive pole of the output end of the second shunt FLQ2 are shorted to each other; a voltmeter DCV is provided between the negative poles of the output ends of the first shunt FLQ1 and the second shunt FLQ2.

[0027] Alternatively, the negative poles of the output ends of the first shunt FLQ1 and the negative pole of the output end of the second shunt FLQ2 are shorted to each other; a voltmeter DCV is provided between the positive poles of the output ends of the first shunt FLQ1 and the second shunt FLQ2.

[0028] Taking the detection of the full scale of 100A as an example, assuming that the current sensor to be measured and the two first shunts FLQ1 and the second FLQ2 are both absolutely accurate without error, then the output voltages of the two shunts are both accurately 4V. After shorting the two positive poles (or shorting the two negative poles), measuring the voltage of the two negative poles (or the two positive poles), the result must be zero.

[0029] In fact, both the sensor and the shunt have errors. Here, a common 6.5-digit voltmeter with a DC100mA range is used, and this voltmeter only needs to have a DC100mA DC voltage range. Since the voltmeter does not directly detect the output signal of the sensor, it actually detects the sum of the sensor error signal and the shunt error signal. This signal is very small, and the voltmeter needs to have a high sensitivity, but does not require a very high accuracy. When measuring the voltage difference of the shunt with the above method, a voltage value will be displayed on the voltmeter. Dividing this voltage value by 4V is the accuracy of the system. Removing the error of the shunt, the accuracy of the sensor is obtained. Since the voltages on the two shunts are in a subtraction relationship, this greatly reduces the accuracy requirement for the current source. Since the voltage difference between the two shunts is measured, this greatly reduces the accuracy requirement for the voltmeter. This is the advantage of this circuit. As mentioned above, the accuracy of the shunt is one order of magnitude higher than that of the sensor, so the error of the shunt can be ignored, and it is considered that the result calculated above is the accuracy of the sensor.

[0030] The key to the working method of this circuit lies in that it uses two shunt resistors to convert two current signals of 100A:100mA into two voltage signals of 4V:4V, converts the precision measurement of the sensor into the measurement of the difference between these two voltage signals, and the precision level of the entire detection system then depends on the precision level of the shunt resistors. It should be noted that the error of the sensor is determined by detecting the voltage difference between the two shunt resistors, namely the shunt resistor in the input circuit and the shunt resistor in the output circuit. Special attention should be paid to the current direction during wiring. Short-circuit the high-potential ends of the two shunt resistors and measure the potential difference between the two low-potential ends. Conversely, short-circuit the low-potential ends and measure the potential difference between the two high-potential ends as well. Since the fluxgate sensor can work bidirectionally, the precision in both directions needs to be detected separately. By simply changing the connection direction of the DCA current source, the bidirectional precision detection of the sensor can be achieved.

[0031] The above embodiments are not limitations on the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the technical solution of the present invention also fall within the protection scope of the present invention.

Claims

1. A detection circuit for a high-precision fluxgate current sensor, characterized in that: include: A front-stage detection circuit connected in series to one side of the input end of the fluxgate current sensor; A post-stage detection circuit connected in series to one side of the output end of the fluxgate current sensor; A direct current source and a first shunt are connected in series to the front-stage detection loop; a second shunt is connected in series to the rear-stage detection loop; The positive pole outputted by the first shunt and the positive pole outputted by the second shunt are short-circuited with each other, and a voltmeter is arranged between the negative pole outputted by the first shunt and the negative pole outputted by the second shunt.

2. The detection circuit for a high-precision fluxgate current sensor according to claim 1, characterized in that: The front-stage detection loop is connected to the primary winding of the fluxgate current sensor.

3. The detection circuit for a high-precision fluxgate current sensor according to claim 1, characterized in that: The post-stage detection loop is connected to the compensation winding of the fluxgate current sensor.

4. A detection circuit for a high-precision fluxgate current sensor, characterized in that: include: A front-stage detection circuit connected in series to one side of the input end of the fluxgate current sensor; A post-stage detection circuit connected in series to one side of the output end of the fluxgate current sensor; A direct current source and a first shunt are connected in series to the front-stage detection loop; a second shunt is connected in series to the rear-stage detection loop; The negative pole outputted by the first shunt and the negative pole outputted by the second shunt are short-circuited with each other, and a voltmeter is arranged between the positive pole outputted by the first shunt and the positive pole outputted by the second shunt.

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