Flexible measuring device for direct-current large current measurement

Abstract

The invention relates to a flexible measuring device for direct current large current measurement. The flexible measuring device comprises an integrated flexible non-contact current probe, a signal conditioning circuit and a signal processing unit, the integrated flexible non-contact current probe comprises a flexible magnetic core, and a magnetic measuring element and a temperature measuring element are integrated in the flexible magnetic core. After an output signal of the integrated flexible non-contact current probe passes through the signal processing unit, an analog signal in linear relation with a to-be-detected current and a digital signal of the to-be-detected current are output; the invention has the advantages of high precision, wide frequency band, low cost, excellent sensitivity and anti-interference capability, and improved measurement precision.

Description

Technical Field

[0001] The invention belongs to the technical field of current sensors, and in particular relates to a flexible measuring device for measuring large direct current. Background Art

[0002] As one of the most important state quantities in key nodes of power transmission and distribution networks and power terminal equipment, current parameters are widely used in power system monitoring and diagnosis. There are many types of current sensors with different principles. Traditional current transformers can only measure AC signals and have disadvantages such as large size and complex installation. Although Rogowski coils have sufficient bandwidth response, small size and low price, they cannot be used for DC current measurement because they measure the differential current. Current measurement technology based on magnetic sensors such as Hall elements, fluxgate devices, and magnetoresistive devices can be applied to the measurement of both AC and DC currents, and has the characteristics of low cost, non-invasiveness and galvanic isolation, making this technology suitable for non-contact measurement of DC current. ; Current measurement technology based on magnetic sensors is usually divided into two structures: without magnetic ring and with magnetic ring. The measurement structure with magnetic ring has a stronger advantage in shielding external magnetic field interference and can improve the sensor's measurement sensitivity. At the same time, it can reduce the measurement error caused by factors such as wire inclination and eccentricity to a certain extent; Due to the existence of the magnetic ring, the shape and size of the probe will be fixed, and it is difficult to use it for current measurement of wires of different shapes and grounding buses of different forms in multiple scenarios, which creates an obstacle to broadening the practical application field of such sensors; Therefore, it is very necessary to provide a flexible measurement device for DC large current measurement with high accuracy, wide bandwidth, low cost, excellent sensitivity and anti-interference ability, and improved measurement accuracy. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a flexible measuring device for measuring large DC currents with high accuracy, wide bandwidth, low cost, excellent sensitivity and anti-interference ability, and improved measurement accuracy.

[0004] The object of the present invention is achieved as follows: a flexible measuring device for measuring large direct current comprises an integrated flexible non-contact current probe and a signal processing unit; the integrated flexible non-contact current probe comprises a flexible magnetic core, a magnetic measuring element and a temperature measuring element are integrated inside the flexible magnetic core; the output signal of the integrated flexible non-contact current probe passes through the signal processing unit, and then outputs an analog signal having a linear relationship with the current to be measured and a digital signal of the current to be measured.

[0005] The flexible magnetic core consists of a flexible magnetic core A and a flexible magnetic core B; the magnetic measuring element is a magnetic sensor; and the temperature measuring element is a temperature sensor.

[0006] The flexible magnetic core A is a flexible magnetic concentrating ring with an air gap; it is made by mixing silicone rubber and soft magnetic material powder, and curing and molding through injection molding.

[0007] The flexible magnetic core B is made by premixing organic silicon prepolymer with soft magnetic material powder.

[0008] The air gap portion of the flexible magnetic core A is pre-filled with the flexible magnetic core B prepared by the pre-mixing step, and includes the steps of embedding the magnetic sensor and the temperature sensor after the pre-filling is completed, and adding a curing agent for curing, so that the flexible magnetic core A and the flexible magnetic core B as a whole form an annular flexible magnetic core without an air gap.

[0009] The soft magnetic material powder is one or more of manganese-zinc ferrite, nickel-zinc ferrite, amorphous alloy, amorphous nanocrystalline magnetic materials with low coercive force and high magnetic permeability.

[0010] The magnetic sensor adopts any one of a Hall effect element, a fluxgate device, an anisotropic magnetoresistive device, a giant magnetoresistive device, and a tunneling magnetoresistive device; the temperature sensor is a thermistor sensor.

[0011] The signal processing unit includes a signal conditioning circuit output buffer amplifier, an ADC-DAC unit and a digital signal processing unit; the signal conditioning circuit includes a signal amplification circuit, a zero adjustment and temperature compensation circuit and a level raising circuit.

[0012] The zero adjustment and temperature compensation circuit calculates the actual compensation voltage through the temperature drift compensation voltage and the zero drift compensation voltage inside the digital signal processing unit, and outputs it to the zero adjustment and temperature compensation circuit after conversion through the ADC-DAC unit.

[0013] The temperature drift compensation voltage is calculated by using the temperature sensor data and the temperature coefficient of the magnetic sensor; the zero drift compensation voltage is calculated by the digital signal processing unit by using the output of the magnetic sensor when no current flows through the conductor to be tested.

[0014] Beneficial effects of the invention: The present invention is a flexible measuring device for measuring large DC currents. During use, the present invention is a flexible magnetic ring that is mixed and molded with silicone rubber and soft magnetic material powder, so that it can ensure the current sensor's shielding ability against external magnetic field interference and measurement sensitivity while solving the pain point that the magnetic ring structure probe has a fixed shape and size, which makes it difficult to apply to current measurement of wires of different shapes and grounding buses of different forms in multiple scenarios; the air gap of the flexible magnetic ring of the present invention is pre-filled with a mixture of silicone prepolymer and soft magnetic material powder, and after the magnetic sensor and the temperature sensor are buried in the pre-filled area, the area is cured, which solves the problem of reduced sensor sensitivity and reduced anti-interference ability due to the presence of a large air gap, and improves the current measurement accuracy of the sensor; the present invention has the advantages of high precision, wide bandwidth, low cost, excellent sensitivity and anti-interference ability, and improved measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is an overall structural diagram of the flexible current sensor of the present invention.

[0016] Figure 2 This is a principle block diagram of the flexible current sensor signal processing unit of the present invention.

[0017] Figure 3 This is the test result of the sensor current linearity of the present invention. DETAILED DESCRIPTION

[0018] In response to the problems raised in the background technology, the present invention provides a flexible current sensor for solving the current measurement of wires of different shapes in multiple scenarios, and improving the sensitivity and anti-interference ability of the sensor, and improving the current measurement accuracy of the sensor; therefore, the flexible current sensor proposed in the present invention that can simultaneously perform AC and DC current measurements and has high accuracy, wide bandwidth and low cost has very important practical significance.

[0019] The present invention will be further described below in conjunction with the accompanying drawings. Example

[0020] like Figure 1-3 As shown, a flexible measuring device for measuring large DC current includes an integrated flexible non-contact current probe and a signal processing unit; the integrated flexible non-contact current probe includes a flexible magnetic core, and a magnetic measuring element and a temperature measuring element are integrated inside the flexible magnetic core; the output signal of the integrated flexible non-contact current probe passes through the signal processing unit to output an analog signal with a linear relationship with the current to be measured and a digital signal of the current to be measured.

[0021] The overall structure of the present invention is as follows Figure 1As shown, the magnetic sensor and the temperature sensor are integrated in the flexible magnetic core of the integrated flexible non-contact current probe; the sensor output signal is output through the signal processing unit to output an analog signal with a linear relationship with the current to be measured and a digital signal of the current to be measured.

[0022] The integrated flexible non-contact current probe part is composed of a flexible magnetic core A, a flexible magnetic core B, a magnetic sensor, and a temperature sensor.

[0023] The flexible magnetic core A is a flexible magnetic concentrating ring with an air gap, which is formed by mixing silicone rubber and soft magnetic material powder and curing by injection molding.

[0024] The flexible magnetic core B is prepared by premixing a silicone prepolymer with soft magnetic material powder, using the mixed material to prefill the air gap of the flexible magnetic core A, burying the magnetic sensor and the temperature sensor after the prefilling, and adding a curing agent for curing to form a ring-shaped flexible magnetic core without air gap.

[0025] The soft magnetic material powder includes but is not limited to manganese zinc ferrite, nickel zinc ferrite, amorphous alloy, amorphous nanocrystals, etc.; it should be particularly noted that due to the existence of electrical connections related to the magnetic sensor and the temperature sensor in the flexible magnetic core B, the soft magnetic material of the flexible magnetic core B should not be a material such as Permalloy with high electrical conductivity; the flexible magnetic core A can be any of the above soft magnetic materials because it has no electrical connection.

[0026] The magnetic sensor includes a Hall effect element, a fluxgate device, an anisotropic magnetoresistance (AMR) device, a giant magnetoresistance (GMR) device, and a tunneling magnetoresistance (TMR) device.

[0027] The temperature sensor may be a sensor device such as a thermistor that is sensitive to temperature changes.

[0028] The signal processing unit principle block diagram is as follows Figure 2 As shown, it includes a signal conditioning circuit, an output buffer amplifier, an ADC-DAC unit and a digital signal processing unit.

[0029] The signal conditioning circuit amplifies, zeroes, and raises the level of the magnetic sensor output signal to output a voltage signal; the voltage signal can directly output an analog signal through an internal output buffer amplifier, or it can output a digital signal through the digital interface of the digital signal processing unit after internal AD conversion.

[0030] The zero adjustment and temperature compensation circuit obtains the actual compensation voltage by calculating the temperature drift compensation voltage and the zero drift compensation voltage inside the digital signal processing unit, and outputs it to the zero adjustment and temperature compensation circuit after DA conversion.

[0031] The temperature drift compensation voltage is calculated by using the temperature sensor data and the temperature coefficient of the magnetic sensor.

[0032] The zero drift compensation voltage is calculated by the digital signal processing unit through the output of the magnetic sensor when no current flows through the conductor to be tested.

[0033] like Figure 3 As shown, a current source is used to generate currents of 5A, 10A, 15A, and 20A to test the linearity of the current sensor of the present invention. The test results show that the sensitivity of the sensor of the present invention is 67.46mV / A, which has a relatively high sensitivity.

[0034] The present invention is a flexible measuring device for measuring large direct current. In use, the present invention is a flexible magnetic ring that is mixed and formed by silicone rubber and soft magnetic material powder, so that it can ensure the current sensor's shielding ability against external magnetic field interference and measurement sensitivity, while solving the pain point that the magnetic ring structure probe is difficult to apply to current measurement of different shapes of wires and different forms of grounding bars in multiple scenarios due to the fixed shape and size of the probe; the air gap of the flexible magnetic ring of the present invention is pre-filled with a mixture of silicone prepolymer and soft magnetic material powder, and after the magnetic sensor and the temperature sensor are buried in the pre-filled area, the area is solidified, which solves the problem of reduced sensor sensitivity and reduced anti-interference ability due to the existence of a large air gap, and improves the current measurement accuracy of the sensor; the present invention has the advantages of high precision, wide frequency band, low cost, excellent sensitivity and anti-interference ability, and improved measurement accuracy. Example

[0035] like Figure 1-3 As shown, a flexible measuring device for measuring large DC current includes an integrated flexible non-contact current probe, a signal conditioning circuit and a signal processing unit; the integrated flexible non-contact current probe includes a flexible magnetic core, and a magnetic measuring element and a temperature measuring element are integrated inside the flexible magnetic core; the output signal of the integrated flexible non-contact current probe passes through the signal processing unit to output an analog signal with a linear relationship with the current to be measured and a digital signal of the current to be measured.

[0036] The flexible current sensor described in the present invention includes an integrated flexible non-contact current probe, a signal conditioning circuit, an ADC-DAC unit, and a digital signal processing unit; the core of the present invention lies in the design of an integrated flexible non-contact current probe formed by curing a flexible magnetic ring formed by curing magnetic powder of a silicone rubber mixed with soft magnetic material and a magnetic sensor and a temperature sensor cured inside the above-mentioned magnetic ring.

[0037] The integrated flexible non-contact current probe can be divided into two parts: A and B: Part A mixes and molds silicone rubber and soft magnetic material powder by injection molding to form a flexible magnetic ring with an air gap.

[0038] Part B is prepared by mixing silicone prepolymer with soft magnetic material powder, and using the mixed fluid material to pre-fill the air gap of the magnetic ring in part A. After the pre-filling is completed, the magnetic sensor and temperature sensor are embedded and a curing agent is added for curing.

[0039] The soft magnetic material powder is one or more magnetic materials with low coercivity and high magnetic permeability such as manganese-zinc ferrite, nickel-zinc ferrite, amorphous alloy, amorphous nanocrystal, etc.; it should be particularly noted that since part B has built-in magnetic sensors and temperature sensors and there is an electrical connection, the soft magnetic material of part B should not be a conductive material, such as high-conductivity Permalloy and other materials; part A can be one or more of any of the above soft magnetic materials because there is no electrical connection.

[0040] The magnetic sensor adopts any one of Hall effect element, anisotropic magnetoresistance (AMR) device, giant magnetoresistance (GMR) device and tunneling magnetoresistance (TMR) device.

[0041] The temperature sensor may be a thermistor, and the measured temperature value is used for temperature compensation of the sensor, especially when the magnetic sensor is a Hall element with a large temperature drift of the output signal.

[0042] The signal processing unit comprises a conditioning circuit, an output buffer amplifier, an ADC-DAC unit and a digital signal processing unit.

[0043] The signal conditioning circuit comprises a signal amplifying circuit, a zero adjustment and temperature compensation circuit, and a level raising circuit.

[0044] The signal amplification circuit is used to adjust the signal sensitivity; the zero adjustment and temperature compensation circuit adjusts the zero point bias and temperature drift of the magnetic sensor to ensure the measurement accuracy of the DC current; the level raising circuit increases the output voltage signal by VCC / 2 so that the output signal meets the ADC sampling signal voltage range.

[0045] In the zero adjustment and temperature compensation circuit, the zero point of the magnetic sensor is measured when there is no current in the internal measured wire, and the zero point compensation voltage is calculated by the digital signal processing unit; and the zero point compensation voltage is synthesized with the temperature compensation voltage calculated by the signal processing unit through the temperature sensor data and the temperature coefficient of the magnetic sensor, and output to the zero adjustment and temperature compensation circuit through the DAC, thereby suppressing the zero point drift and temperature drift.

[0046] In summary, the present invention proposes a flexible magnetic ring, which can ensure the current sensor's shielding ability against external magnetic field interference and measurement sensitivity, while solving the pain point that the magnetic ring structure probe has a fixed shape and size, making it difficult to apply to current measurement of different shapes of wires and different forms of grounding buses in multiple scenarios.

[0047] In the present invention, the air gap of the flexible magnetic ring is pre-filled with a mixture of silicone prepolymer and soft magnetic material powder, and then the magnetic sensor and the temperature sensor are integrated inside the flexible magnetic ring and cured; the problem of reduced sensor sensitivity and reduced anti-interference ability due to the presence of a large air gap is solved, and the current measurement accuracy of the sensor is improved.

[0048] The present invention is a flexible measuring device for measuring large direct current. In use, the present invention is a flexible magnetic ring that is mixed and formed by silicone rubber and soft magnetic material powder, so that it can ensure the current sensor's shielding ability against external magnetic field interference and measurement sensitivity, while solving the pain point that the magnetic ring structure probe is difficult to apply to current measurement of different shapes of wires and different forms of grounding bars in multiple scenarios due to the fixed shape and size of the probe; the air gap of the flexible magnetic ring of the present invention is pre-filled with a mixture of silicone prepolymer and soft magnetic material powder, and after the magnetic sensor and the temperature sensor are buried in the pre-filled area, the area is solidified, which solves the problem of reduced sensor sensitivity and reduced anti-interference ability due to the existence of a large air gap, and improves the current measurement accuracy of the sensor; the present invention has the advantages of high precision, wide frequency band, low cost, excellent sensitivity and anti-interference ability, and improved measurement accuracy.

Claims

1. A flexible measuring device for measuring large DC current, characterized in that: It comprises an integrated flexible non-contact current probe and a signal processing unit; the integrated flexible non-contact current probe comprises a flexible magnetic core, and a magnetic measuring element and a temperature measuring element are integrated inside the flexible magnetic core; the output signal of the integrated flexible non-contact current probe passes through the signal processing unit to output an analog signal having a linear relationship with the current to be measured and a digital signal of the current to be measured.

2. A flexible measuring device for measuring large DC current according to claim 1, characterized in that: The flexible magnetic core is composed of a flexible magnetic core A and a flexible magnetic core B; the magnetic measuring element is a magnetic sensor; and the temperature measuring element is a temperature sensor.

3. A flexible measuring device for measuring large DC current according to claim 2, characterized in that: The flexible magnetic core A is a flexible magnetic concentrating ring with an air gap; it is made by mixing silicone rubber and soft magnetic material powder, and curing and molding through injection molding.

4. A flexible measuring device for measuring large DC current according to claim 3, characterized in that: The flexible magnetic core B is made by premixing organic silicon prepolymer with soft magnetic material powder.

5. A flexible measuring device for measuring large DC current according to claim 4, characterized in that: The air gap portion of the flexible magnetic core A is pre-filled with the flexible magnetic core B made by the pre-mixing step described in claim 4, and includes the steps of burying the magnetic sensor and the temperature sensor after the pre-filling is completed, and adding a curing agent for curing, so that the flexible magnetic core A and the flexible magnetic core B as a whole form an annular flexible magnetic core without an air gap.

6. A flexible measuring device for measuring large DC current according to claim 3 or 4, characterized in that: The soft magnetic material powder is one or more of manganese-zinc ferrite, nickel-zinc ferrite, amorphous alloy, amorphous nanocrystalline magnetic materials with low coercive force and high magnetic permeability.

7. A flexible measuring device for measuring large DC current according to claim 2, characterized in that: The magnetic sensor adopts any one of a Hall effect element, a fluxgate device, an anisotropic magnetoresistive device, a giant magnetoresistive device, and a tunneling magnetoresistive device; the temperature sensor is a thermistor sensor.

8. A flexible measuring device for measuring large DC current according to claim 1, characterized in that: The signal processing unit includes a signal conditioning circuit output buffer amplifier, an ADC-DAC unit and a digital signal processing unit; the signal conditioning circuit includes a signal amplification circuit, a zero adjustment and temperature compensation circuit and a level raising circuit.

9. A flexible measuring device for measuring large DC current according to claim 8, characterized in that: The zero adjustment and temperature compensation circuit calculates the actual compensation voltage through the temperature drift compensation voltage and the zero drift compensation voltage inside the digital signal processing unit, and outputs it to the zero adjustment and temperature compensation circuit after conversion through the ADC-DAC unit.

10. A flexible measuring device for measuring large DC current according to claim 9, characterized in that: The temperature drift compensation voltage is calculated by using the temperature sensor data and the temperature coefficient of the magnetic sensor; the zero drift compensation voltage is calculated by the digital signal processing unit by using the output of the magnetic sensor when no current flows through the conductor to be tested.

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