A probe and single probe dual range fluxgate current sensor

Abstract

The present application belongs to the technical field of fluxgate, discloses a kind of probe and single-probe double-range fluxgate current sensor, the present application is measured by two large-scale current measuring coils and two small-scale current measuring coils probe, can realize that one fluxgate current sensor measures two range range AC and DC current, small-scale current measurement range is ±10mA, resolution can reach 1 μA level, large-scale current measurement range is ±10A, resolution can reach 1mA level.The sensor of the present application can realize the switching of current measurement range by microprocessor function module, after switching, the impedance of relevant circuit is matched according to selected circuit, uses preamplifier circuit, carries out differential output to the two sensing coils of selected range, can suppress common-mode noise signal.

Description

Technical Field

[0001] This invention belongs to the field of fluxgate technology, specifically relating to a probe and a single-probe dual-range fluxgate current sensor. Background Technology

[0002] Fluxgate phenomenon is a ubiquitous electromagnetic induction phenomenon that obeys Faraday's law of electromagnetic induction. Applying an alternating current to the excitation coil of a detection probe causes the magnetic core to fluctuate between supersaturation and unsaturation. When the ambient magnetic field changes, the magnetic flux in the core changes, causing the core to saturate earlier or later. Based on the nonlinear relationship between the saturated core and the ambient magnetic field, the strength of the ambient magnetic field can be inferred. Due to this characteristic, fluxgate technology has significant advantages, and current sensors made using fluxgate technology exhibit extremely high resolution and sensitivity.

[0003] Fluxgate probes have no theoretical sensitivity threshold limitation. To improve the resolution of fluxgate current sensors for small currents, the distance between the fluxgate sensor probe and the coil under test should be as close as possible. For large current detection, the distance between the fluxgate sensor probe and the coil under test should be relatively far to attenuate the magnetic induction intensity.

[0004] Currently, when using fluxgate current sensors to detect currents of different ranges, different ranges are often required, which causes many inconveniences in practical applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a probe and a single-probe dual-range fluxgate current sensor that can measure large currents as well as small-range currents down to the microampere level, and improves sensitivity and reduces noise.

[0006] To achieve the above objectives, a probe includes two large-range current measuring coils and two small-range current measuring coils. Both the large-range and small-range current measuring coils include annular frames with circumferentially grooved grooves. Magnetic cores are wound within the grooves. The number of turns of the magnetic core in the large-range current measuring coil is 10 times the number of turns of the magnetic core in the small-range current measuring coil. Excitation coils and induction coils are wound on the annular frames. The induction coil passes through four annular frames, and the excitation coil can be reused as a feedback coil.

[0007] The inner diameter of the ring-shaped frame of the large-range current measuring coil is 12-16 mm, and the outer diameter is 15-19 mm.

[0008] The inner diameter of the ring-shaped frame of the small-range current measuring coil is 6-10 mm, and the outer diameter is 9-13 mm.

[0009] The outer diameter of the ring frame of both the large-range current measuring coil and the small-range current measuring coil is 3-5 mm larger than the inner diameter.

[0010] The depth of the groove on the ring skeleton is half the outer diameter of the ring skeleton minus half the inner diameter plus half the thickness of the magnetic core.

[0011] The magnetic core is made of permalloy strip, cobalt-based amorphous strip or nanocrystalline strip.

[0012] The magnetic core of the large-range current measuring coil has 10 to 100 turns.

[0013] The number of turns of the magnetic core of the small-range current measuring coil is 1 to 10.

[0014] The two excitation coils used for the same measurement range are wound in opposite directions, while the feedback coil is wound in the same direction.

[0015] A single-probe dual-range fluxgate current sensor includes a probe, the probe being connected to a preamplifier circuit, the preamplifier circuit being connected to a bandpass filter circuit, the bandpass filter circuit being connected to a phase-sensitive detector circuit, the phase-sensitive detector circuit being connected to an integrating circuit, the integrating circuit being connected to a power amplifier circuit, the power amplifier circuit being connected to a test output terminal and a microprocessor functional module, and the microprocessor functional module being connected to a host computer and the probe.

[0016] The host computer is used to send control information;

[0017] The microprocessor function module is used to adjust the amplitude of the excitation signal sent to the excitation coil according to the control information sent by the host computer, so that the amplitude of the current signal in the excitation coil is different from that in the feedback coil.

[0018] The microprocessor functional module includes a range switching circuit and an analog-to-digital conversion circuit. One end of the range switching circuit is connected to the power amplifier circuit, and the other end is connected to the selected excitation signal generation circuit. The unselected excitation signal generation circuit is connected to the range switching circuit as a feedback coil. The range switching circuit is controlled by the host computer.

[0019] Analog-to-digital converter circuit is used to convert the analog voltage signal in the feedback loop into a digital signal and transmit it to the host computer.

[0020] The preamplifier circuit uses an operational amplifier and an adjustable resistor to limit the voltage signal amplification range to 1 to 10 times.

[0021] The phase-sensitive detector circuit is used to phase-shift the input second harmonic excitation signal, and uses the phase-shifted second harmonic signal as a switch to control the conduction and cutoff of the second harmonic sinusoidal signal.

[0022] Compared with the prior art, the present invention uses a probe composed of two large-range current measuring coils and two small-range current measuring coils to realize the measurement of AC and DC current in two ranges by a fluxgate current sensor. The small-range current measurement range is ±10mA with a resolution of up to 1μA level, and the large-range current measurement range is ±10A with a resolution of up to 1mA level.

[0023] Furthermore, the present invention has an excitation coil and an induction coil wound on the annular frame. The induction coil passes through four annular frames. The excitation coil can be reused as a feedback coil. The two excitation coils used for the same range measurement are wound in opposite directions, while the feedback coil is wound in the same direction. The present invention reuses the excitation coil of the unselected range probe to participate in the current measurement in the form of a compensation coil. This can improve the current measurement stability, reduce the probe volume, and lower the cost while making the fluxgate probe structure more compact.

[0024] The sensor of this invention enables switching of current measurement ranges via a microprocessor module. After switching, the impedance of the relevant circuits is matched according to the selected circuit, and a pre-amplifier circuit is used to differentially output the two induction coils of the selected range, which can further suppress common-mode noise signals. The fluxgate current sensor of this invention can achieve a resolution of 1μA, with a measurement range of ±10mA for the small current measurement range and ±10A for the large current measurement range. The bandwidth of the small current measurement range can reach 1kHz, and the bandwidth of the large current measurement range can reach 10kHz, with linearity and accuracy both at 0.1%. Attached Figure Description

[0025] Figure 1 This is a simulation diagram of the fluxgate current sensor probe of the present invention;

[0026] Figure 2 This is a block diagram of the fluxgate current sensor system of the present invention;

[0027] Figure 3 This is a functional block diagram of the microprocessor of the present invention;

[0028] Among them, 1. Large-range current measuring coil; 2. Small-range current measuring coil; 3. Preamplifier circuit; 4. Phase-sensitive detector circuit; 6. Integrator circuit; 7. Power amplifier circuit; 8. Test output terminal; 9. Microprocessor functional module; 11. Range switching circuit; 12. Analog-to-digital conversion circuit; 13. Magnetic core. Detailed Implementation

[0029] The invention will now be further described with reference to the accompanying drawings.

[0030] See Figure 1A probe includes two large-range current measuring coils 1 and two small-range current measuring coils 2. Both the large-range current measuring coils 1 and the small-range current measuring coils 2 include annular frames with grooves circumferentially formed on the annular frames. Magnetic cores 13 are wound within the grooves. The number of turns of the magnetic core 13 in the large-range current measuring coils 1 is 10 times the number of turns of the magnetic core 13 in the small-range current measuring coils 2. Excitation coils and induction coils are wound at equal intervals on the annular frames. The induction coils pass through four annular frames. The excitation coils can be reused as feedback coils. The two excitation coils used for measuring the same range are wound in opposite directions, while the feedback coils are wound in the same direction.

[0031] Preferably, the inner diameter of the annular frame of the large-range current measuring coil 1 is 12-16 mm, and the outer diameter is 15-19 mm.

[0032] Preferably, the inner diameter of the annular frame of the small-range current measuring coil 2 is 6-10 mm, and the outer diameter is 9-13 mm.

[0033] Preferably, the outer diameter of the annular frame of both the large-range current measuring coil 1 and the small-range current measuring coil 2 is 3-5 mm larger than the inner diameter.

[0034] Preferably, the groove depth on the annular skeleton is half the outer diameter of the annular skeleton minus half the inner diameter plus half the thickness of the magnetic core.

[0035] Preferably, the magnetic core 13 is made of permalloy strip, cobalt-based amorphous strip or nanocrystalline strip.

[0036] Preferably, the magnetic core 13 of the large-range current measuring coil 1 has 10 to 100 turns.

[0037] Preferably, the number of turns of the magnetic core 13 of the small-range current measuring coil 2 is 1 to 10.

[0038] See Figure 2 A single-probe, dual-range fluxgate current sensor includes a probe connected to a preamplifier circuit 3, which in turn connects to a bandpass filter circuit 4. The bandpass filter circuit 4 is connected to a phase-sensitive detector circuit 5, which is connected to an integrating circuit 6. The integrating circuit 6 is connected to a power amplifier circuit 7, which is connected to a test output terminal 8 and a microprocessor module 9. The microprocessor module 9 is connected to a host computer and the probe. The test output 8 allows for easy waveform display on an oscilloscope during debugging.

[0039] The host computer is used to send control information; the microprocessor module 9 is used to adjust the amplitude of the excitation signal sent to the excitation coil according to the control information sent by the host computer, so that the amplitude of the current signal in the excitation coil is different from that in the feedback coil. The microprocessor module 9 can generate a variety of excitation signals, such as square wave signals, sine wave signals, and triangle wave signals, all of which can be adjusted in frequency and amplitude.

[0040] After an excitation current is applied to the excitation coil, the high-permeability magnetic core 13 will change between oversaturation and unsaturation. At this time, the induction coil generates an induced voltage signal. The amplitude of the directly output induced voltage signal is relatively small. It is first amplified by the preamplifier circuit 3, and then filtered by the bandpass filter circuit 4 to remove noise and interference and extract the second harmonic. The magnitude of the even harmonic in the induced voltage signal can reflect the magnitude of the magnetic field in the high-permeability magnetic core 13 and indirectly reflect the magnitude of the current. The second harmonic with the largest amplitude among the even harmonics is used for measurement. The induced voltage signal is then processed by the phase-sensitive detector circuit 5 for phase shifting and detection, and a full-wave signal is output to determine the positive or negative current. After that, the signal is filtered into a DC signal by the integrator circuit 6 and output to the power amplifier circuit 7 for feedback drive.

[0041] See Figure 3 The microprocessor functional module 9 includes a range switching circuit 11 and an analog-to-digital conversion circuit 12. One end of the range switching circuit 11 is connected to a power amplifier circuit, and the other end is connected to a first excitation signal generation circuit, a second excitation signal generation circuit, and a feedback loop. The range switching circuit 11 is controlled by a host computer. The excitation signal waveforms and frequencies of the first excitation signal generation circuit and the second excitation signal generation circuit are the same, but the amplitudes are different.

[0042] The analog-to-digital converter circuit 12 is used to convert the analog voltage signal in the feedback loop into a digital signal and transmit it to the host computer. After the voltage signal is converted into a digital signal, it is sampled and transmitted to the host computer. The sampling frequency is above 200kS / s.

[0043] Preferably, the preamplifier circuit 3 uses an operational amplifier and an adjustable resistor to limit the voltage signal amplification range to 1 to 10 times.

[0044] Preferably, the phase-sensitive detector circuit 5 is used to phase-shift the input second harmonic excitation signal, and uses the phase-shifted second harmonic signal as a switch to control the conduction and cutoff of the second harmonic sinusoidal signal.

[0045] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the present invention are within the protection scope of the present invention.

Claims

1. A single-probe dual-range fluxgate current sensor, characterized in that, The system includes a probe, which is connected to a preamplifier circuit (3), which is connected to a bandpass filter circuit (4), which is connected to a phase-sensitive detector circuit (5), which is connected to an integrator circuit (6), which is connected to a power amplifier circuit (7), which is connected to a test output terminal (8) and a microprocessor function module (9), which is connected to a host computer and the probe. The host computer is used to send control information; The microprocessor function module (9) is used to adjust the amplitude of the excitation signal sent to the excitation coil according to the control information sent by the host computer, so that the amplitude of the current signal in the excitation coil is different from that in the feedback coil. The microprocessor functional module (9) includes a range switching circuit (11) and an analog-to-digital conversion circuit (12). One end of the range switching circuit (11) is connected to the power amplifier circuit, and the other end is connected to the selected excitation signal generation circuit. The unselected excitation coil is connected to the range switching circuit (11) as a feedback coil. The range switching circuit (11) is controlled by the host computer. Analog-to-digital converter circuit (12) is used to convert the analog voltage signal in the feedback loop into a digital signal and transmit it to the host computer; The probe includes two large-range current measuring coils (1) and two small-range current measuring coils (2). Both the large-range current measuring coil (1) and the small-range current measuring coil (2) include a ring frame with grooves on the circumference of the ring frame. A magnetic core (13) is wound in the groove. The number of turns of the magnetic core of the large-range current measuring coil (1) is 10 times the number of turns of the magnetic core of the small-range current measuring coil (2). An excitation coil and an induction coil are wound on the ring frame. The induction coil passes through four ring frames. The excitation coil can be reused as a feedback coil. The inner diameter of the ring frame of the large-range current measuring coil (1) is 12~16mm and the outer diameter is 15~19mm; The inner diameter of the ring frame of the small-range current measuring coil (2) is 6~10mm and the outer diameter is 9~13mm; The outer diameter of the ring frame of both the large-range current measuring coil (1) and the small-range current measuring coil (2) is 3~5mm larger than the inner diameter; The number of turns of the magnetic core of the large-range current measuring coil (1) is 10~100; The number of turns of the magnetic core of the small-range current measuring coil (2) is 1~10 turns; The two excitation coils used for the same measurement range are wound in opposite directions, while the feedback coil is wound in the same direction.

2. The single-probe dual-range fluxgate current sensor according to claim 1, characterized in that, The depth of the groove on the ring skeleton is half the outer diameter of the ring skeleton minus half the inner diameter plus half the thickness of the magnetic core.

3. The single-probe dual-range fluxgate current sensor according to claim 1, characterized in that, The magnetic core is made of permalloy strip, cobalt-based amorphous strip or nanocrystalline strip.

4. The single-probe dual-range fluxgate current sensor according to claim 1, characterized in that, The preamplifier circuit (3) uses an operational amplifier and an adjustable resistor to limit the voltage signal amplification range to 1~10 times.

5. A single-probe dual-range fluxgate current sensor according to claim 1, characterized in that, The phase-sensitive detector circuit (5) is used to phase-shift the input double frequency excitation signal and use the phase-shifted double frequency signal as a switch to control the conduction and cutoff of the second harmonic sinusoidal signal.

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