CN207866886U - A kind of magnetic modulator current sensing means - Google Patents
A kind of magnetic modulator current sensing means Download PDFInfo
- Publication number
- CN207866886U CN207866886U CN201820362444.3U CN201820362444U CN207866886U CN 207866886 U CN207866886 U CN 207866886U CN 201820362444 U CN201820362444 U CN 201820362444U CN 207866886 U CN207866886 U CN 207866886U
- Authority
- CN
- China
- Prior art keywords
- coil
- feedback
- input terminal
- resistance
- magnetic modulator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
Abstract
A kind of magnetic modulator current sensing means, including magnetic modulator, shaping circuit, filter circuit and feedback circuit, magnetic modulator include iron core T1 and iron core T2, and excitation coil W3 is connected with excitation coil W7 differential concatenations；Sampling coil W1 is connected with sampling coil W5 differential concatenations；Detection coil W2 is connected with detection coil W6 series aiding connections；Feedback coil W4 is connected with feedback coil W8 series aiding connections；Shaping circuit input terminal is connected with magnetic modulator output end C；Shaping circuit output end is connected with the input terminal M of filter circuit；The input terminal N of filter circuit and the C ' connections of magnetic modulator output end；The input terminal of feedback circuit is connect with filter circuit output end；Feedback circuit output is connected with the ends magnetic modulator F.The utility model has many advantages, such as high certainty of measurement, and simple in structure, performance is stable and strong antijamming capability.
Description
Technical field
The utility model belongs to direct current detection field, and in particular to a kind of magnetic modulator current sensing means.
Background technology
Currently, the detection of DC low current is essentially all the frequency multiplication mediation practices for using and being constituted as core using magnetic modulator
Come what is measured.Frequency multiplication magnetic modulation principle is to extract the second harmonic in magnetic modulator output signal as effective information,
DC current is detected using the size of its amplitude.But also includes other harmonic components in magnetic modulator output information, need
The amplitude for carrying out the higher second harmonic component for being filtered, and taking out is typically small, in addition it is also necessary to more complicated
Demodulator circuit detects the polarity of tested electric current, it is easy to be interfered.
Invention content
The purpose of this utility model is that the existing DC low current measuring device of solution is complicated, and poor anti jamming capability is asked
Topic, while improving measurement accuracy.
Technical solutions of the utility model are a kind of magnetic modulator current sensing means, including magnetic modulator, shaping circuit, filter
Wave circuit and feedback circuit, magnetic modulator include iron core T1 and iron core T2, and sampling coil W1, detection coil are wound on iron core T1
W2, excitation coil W3 and feedback coil W4 are wound with sampling coil W5, detection coil W6, excitation coil W7 and feedback on iron core T2
Coil W8；Excitation coil W3 is connected with excitation coil W7 differential concatenations, excitation coil W3 other ends A and the excitation coil W7 other ends
A ' is electrically connected as magnetic modulator exciting current input terminal with city；Sampling coil W1 is connected with sampling coil W5 differential concatenations, is adopted
Line-transect circle W1 other ends B and sampling coil W5 other ends B ' is used as magnetic modulator input terminal, for inputting tested electric current；Detection line
Circle W2 is connected with detection coil W6 series aiding connections, and detection coil W2 other ends C ' and detection coil W6 other ends C are modulated as magnetic
Device output end；Feedback coil W4 is connected with feedback coil W8 series aiding connections, the other end F ' and feedback coil W8 of feedback coil W4
Other end F as magnetic modulator feedback current input terminal；Shaping circuit input terminal is connected with magnetic modulator output end C；Shaping
Circuit output end is connected with the input terminal M of filter circuit；The input terminal N of filter circuit and the C ' connections of magnetic modulator output end；Instead
The input terminal of current feed circuit is connect with filter circuit output end；The ends F of feedback circuit output and magnetic modulator feedback coil W8 connect
It connects；One end and the ends F ' of magnetic modulator feedback coil W4 connect after resistance R0 and voltmeter V parallel connections, resistance R0 other ends ground connection.
Further, the shaping circuit is metrosil D.
Further, the filter circuit is active low-pass filter circuit, including operational amplifier U1, resistance R1, resistance
R2, capacitance C1 and capacitance C2, resistance R1 and resistance R2 are connected in series with, and the other end of R1 is another as filter circuit input terminal M, R2
One end is connect with operational amplifier U1 in-phase input ends；The output of the inverting input and operational amplifier U1 of operational amplifier U1
End connection；One end of capacitance C1 is connect with resistance R1 and resistance R2 tie points, and the capacitance C1 other ends are as filter circuit input terminal
N；One end of capacitance C2 is connect with the in-phase input end of operational amplifier U1, and the other end is connect with filter circuit input terminal N；Fortune
Output end P of the output end of amplifier U1 as filter circuit is calculated, the output end Q of filter circuit is connect with input terminal N.
Further, the feedback circuit includes operational amplifier U2, resistance R3, resistance R4, resistance R5 and capacitance C3；Electricity
Resistance R3, capacitance C3 and resistance R4 are sequentially connected in series, and for the resistance R3 other ends as feedback circuit input terminal X, resistance R4's is another
End is connect with the output end of operational amplifier U2, and inverting input and resistance R3, the junctions capacitance C3 of operational amplifier U2 connect
It connects；One end of resistance R5 is connect with the in-phase input end of operational amplifier U2, the other end ground connection of resistance R5；Operational amplifier U2
Input terminal Y of the in-phase input end as feedback circuit；The input terminal X of feedback circuit is connect with filter circuit output end Q, feedback
The input terminal Y of circuit is connect with filter circuit output end P.
Further, the voltmeter V is selectedBit digital gauge outfit, for showing current detecting result.
The operation principle of the utility model：When tested electric current, that is, magnetic modulator input current I=0, stationary magnetic field in iron core
Intensity H0=0, magnetic modulator output voltage u0Positive wave crest Um+, negative peak Um- it is equal, Um+=Um-；Work as I>When 0, H0≠ 0,
u0Positive wave crest, negative peak it is unequal, there is wave crest difference Δ Um=Um+-Um-, wave crest difference Δ UmSize and tested electric current I at just
It is positive and negative more consistent with the tested polarity of electric current I than, wave crest difference.To u0It is obtained and Δ U after carrying out Shape correctionmEqual Δ Um',
Its DC component is obtained using low-pass filtering treatment, you can acquisition can reflect tested direct current size and polar DC voltage,
Be linked on feedback coil using feedback circuit, constitute a closed-loop system, the magnetic potential generated using feedback current with it is tested
Magnetic potential the characteristics of balancing each other that electric current generates, measures tested electric current.
The utility model has the beneficial effects that：By detecting the size of magnetic modulator output DC component and positive and negative reflecting
The size and polarity of tested electric current, to realize the measurement of DC low current, simple in structure, strong antijamming capability；Pass through feedback
Circuit makes measuring device have non differential regulation characteristic, greatlys improve measurement accuracy.
Description of the drawings
The utility model is described in further detail with reference to the accompanying drawings and examples.
Fig. 1 is the utility model circuit structure block diagram.
Fig. 2 is the utility model circuit diagram.
Fig. 3 is magnetic modulator output voltage u0Oscillogram, be tested electric current I=0.
Fig. 4 is magnetic modulator output voltage u0Oscillogram, be tested electric current I>0.
Fig. 5 is output voltage u' after shaping0Oscillogram, I=0.
Fig. 6 is output voltage u' after shaping0Oscillogram, I>0.
Specific implementation mode
As depicted in figs. 1 and 2, a kind of magnetic modulator current sensing means, including magnetic modulator, shaping circuit, filtered electrical
Road and feedback circuit, magnetic modulator include iron core T1 and iron core T2, and sampling coil W1 is wound on iron core T1, detection coil W2, is swashed
Coil W3 and feedback coil W4 are encouraged, sampling coil W5, detection coil W6, excitation coil W7 and feedback coil are wound on iron core T2
W8；Excitation coil W3 is connected with excitation coil W7 differential concatenations, and excitation coil W3 other ends A and excitation coil W7 other ends A ' make
It is electrically connected with city for magnetic modulator exciting current input terminal；Sampling coil W1 is connected with sampling coil W5 differential concatenations, samples line
It encloses W1 other ends B and sampling coil W5 other ends B ' and is used as magnetic modulator input terminal, for inputting tested electric current；Detection coil W2
It is connected with detection coil W6 series aiding connections, detection coil W2 other ends C ' and detection coil W6 other ends C are defeated as magnetic modulator
Outlet；Feedback coil W4 is connected with feedback coil W8 series aiding connections, and the other end F's ' and feedback coil W8 of feedback coil W4 is another
One end F is as magnetic modulator feedback current input terminal；Shaping circuit input terminal is connected with magnetic modulator output end C；Shaping circuit
Output end is connected with the input terminal M of filter circuit；The input terminal N of filter circuit and the C ' connections of magnetic modulator output end；Feedback electricity
The input terminal on road is connect with filter circuit output end；Feedback circuit output is connected with the ends F of magnetic modulator feedback coil W8；Electricity
The F ' of one end and magnetic modulator feedback coil W4 hold connection, resistance R0 other ends ground connection after hindering R0 and voltmeter V parallel connections.Each coil
Same Name of Ends with () mark in fig. 2.
The shaping circuit used is metrosil D.
The filter circuit used is active low-pass filter circuit, including operational amplifier U1, resistance R1, resistance R2, capacitance
C1 and capacitance C2, resistance R1 and resistance R2 are connected in series with, and the other end of R1 is as filter circuit input terminal M, the R2 other end and fortune
Calculate the connection of amplifier U1 in-phase input ends；The inverting input of operational amplifier U1 is connect with the output end of operational amplifier U1；
One end of capacitance C1 is connect with resistance R1 and resistance R2 tie points, and the capacitance C1 other ends are as filter circuit input terminal N；Capacitance C2
One end connect with the in-phase input end of operational amplifier U1, the other end is connect with filter circuit input terminal N；Operational amplifier U1
Output end P of the output end as filter circuit, the output end Q of filter circuit connect with input terminal N.
The feedback circuit used includes operational amplifier U2, resistance R3, resistance R4, resistance R5 and capacitance C3；Resistance R3, electricity
Hold C3 and resistance R4 to be sequentially connected in series, the resistance R3 other ends are as feedback circuit input terminal X, the other end of resistance R4 and operation
The output end of amplifier U2 connects, and the inverting input of operational amplifier U2 is connect with resistance R3, the junctions capacitance C3；Resistance R5
One end connect with the in-phase input end of operational amplifier U2, the other end of resistance R5 ground connection；Operational amplifier U2's is same mutually defeated
Enter input terminal Y of the end as feedback circuit；The input terminal X of feedback circuit is connect with filter circuit output end Q, feedback circuit it is defeated
Enter to hold Y to be connect with filter circuit output end P.
The voltmeter V used is selectedBit digital gauge outfit, for showing current detecting result.
As shown in Fig. 2, magnetic modulator exciting current input terminal A and input terminal A are connect with 220V AC powers.
The magnetic modulator used, two core characteristics are consistent with size.Excitation coil W3 on two iron cores and excitation coil
W7 equal turn numbers, and Same Name of Ends Opposite direction connection, then composition bridge is connect with excitation alternating-current voltage source, detection signal is connected to shaping
Circuit and filter circuit.This magnetic modulator has the function of making the odd harmonic of magnetic flux to cancel out each other, even-order harmonic is superimposed,
Therefore, even-order harmonic component is only contained in magnetic modulator output signal, Shape correction is first carried out by antithesis order harmonic components, then
It carries out low-pass filtering treatment and obtains its DC component, u0Just reflect the size of DC component, and u0Average value i.e. its direct current point
Amount is proportional to Δ Um, can reflect tested direct current size and polar DC voltage to obtain, using feedback circuit to straight
Stream voltage signal is amplified and correction process, and feedback circuit shares a piece of 4 operational amplifier with active filter circuit and integrates core
Piece (model is LM324), simplifies the structure of measuring device, and anti-interference ability is stronger.
The model 2CW52 of the bi-directional voltage stabilizing pipe used, the range of burning voltage is between 3.2~4.5V, threshold voltage
For 0.7V, by partly removing by a narrow margin for magnetic modulator output signal, to obtain the sharp chong channel wave of rule.
Active low-pass filter circuit cutoff frequency is 3.6Hz.
The feedback circuit used uses pi regulator, and the existing scale operation of the circuit has integral operation again, to DC voltage
Signal is amplified and correction process, and the device is made to have non differential regulation characteristic.
Tested electric current I is accessed into magnetic modulator input terminal B-B', as tested electric current I=0, constant magnetic in iron core when measurement
Field intensity H0=0, magnetic modulator output voltage u0Positive wave crest and negative wave peak-to-peak value are equal, Um+=Um-, as shown in Figure 3.Work as I>0
When, H0≠ 0, make H in the exchange magnetic potential of exchange positive half cycle0The iron core consistent with magnetic potential direction is exchanged is introduced into saturation, and another
Enter saturation after iron core.After one of iron core enters saturation, d φ/dt decline, so sinusoidal voltage is largely applied
It is added on the iron-core coil for not entering saturation region also, allows for u in this way0There is a peak voltage.And it is handed in exchange negative half period
Stream magnetic potential just with exchange positive half cycle on the contrary, another iron core is made to be introduced into saturation, equally, u0Still there is peak voltage output.
The hysteresis loop B-H of two iron cores is inconsistent in practice, u0Positive wave crest, negative wave peak-to-peak value it is unequal, there is wave crest peak difference Δ Um=
Um+-Um-, as shown in Figure 4.Peak difference Δ UmSize it is directly proportional to tested direct current I, peak difference it is positive and negative consistent with the polarity of I.
In order to directly measure Δ Um, the utility model is using the shaping circuit of bi-directional voltage stabilizing pipe composition by Fig. 3, Fig. 4
Waveform u0In dash area remove, (meet the cutoff frequency of filter circuit using by the active low-pass filter circuit in Fig. 2
Less than output signal u0Fundamental frequency), Fig. 5, sharp pulse voltage waveform u shown in fig. 6 can be respectively obtained0'。u0' for just,
Negative waveform of sharp pulses.If the threshold voltage of shaping circuit is Ug, then when | u0| ＜ UgWhen, u0'=0；When | u0|≥UgWhen, u0'
=u0-Ug。 u0' peak difference Δ Um'=Um+'-Um-'=(Um+-Ug)-(Um--Ug)=Δ Um, because of u0' peak difference Δ Um' and u0's
Peak difference Δ UmIt is equal, therefore u can be utilized0' peak difference Δ Um' size and polarity reflect the size of tested DC low current I
And polarity.According to Fourier space it is found that output signal u0' average value be proportional to its wave crest difference Δ Um', output signal u0'
Average value namely its DC component therefore can be to u0' carry out low-pass filtering obtain its DC component to obtain peak difference Δ Um'
Size and polarity.
By the peak difference Δ U of acquisitionm' by the amplification and correction process of feedback loop circuit, it is linked into feedback coil and is formed
One closed-loop system, it is equal with the magnetic potential that tested electric current generates using the magnetic potential that feedback regulation effect makes feedback current generate
Therefore weighing apparatus is tested electric current I and normallized current I0Relationship be represented by I=W4I0/W1, wherein W1For sampling coil W1 and adopt
Line-transect circle W5 the number of turns, W4For the number of turns of feedback coil W4 and feedback coil W8.Output voltage U0For electric current I0In fixed value resistance R0
The pressure drop of upper generation, I can be expressed as I=W again4U0/W1R0。
In a kind of embodiment, it is 1 to be tested the sampling coil W1 of electric current and sampling coil W5 the number of turns, feedback coil W4 and feedback
The number of turns of coil W8 is 1, and resistance R0 is 100 Ω, I=U0/ 100, selectionThe full scale of bit digital gauge outfit is 2000mV,
Resolution ratio is 1mV, and the measurement range of the measuring device is 10 μ A~20mA.It, can be anti-by changing to change measurement range
The number of turns W of feeder line circle W4 and feedback coil W84To realize.In addition, feedback line in DC low current measuring device in the present embodiment
Circle is designed to the form with tap, is switched by change-over switch, is detected to different size DC low current with realizing.
The feedback circuit of type DC small current detector uses pi regulator in the present embodiment, therefore detects theoretical when electric current
On be not no error, the error of type DC small current detector, which is solely dependent upon, is connected in parallel on fixed value resistance R0The essence of upper display instrument
Degree.Therefore, the accuracy of detection of this type DC small current detector is very high.
The utility model is using the device for directly detecting magnetic modulator DC component, by detecting the straight of magnetic modulator output
The size of flow component and it is positive and negative reflect the size and Orientation of tested electric current, effectively simplify the structure of circuit, solve existing straight
It is complicated to flow small current measurement apparatus structure, the problem of poor anti jamming capability, while additional feedback circuit, to d. c. voltage signal into
The characteristics of row amplification and correction process, the magnetic potential that the magnetic potential generated using feedback current is generated with tested electric current balances each other, measures
Tested electric current, greatly improves measurement accuracy.
Claims (4)
1. a kind of magnetic modulator current sensing means, including magnetic modulator, shaping circuit and filter circuit, which is characterized in that also
Including feedback circuit, magnetic modulator includes iron core T1 and iron core T2, and sampling coil W1 is wound on iron core T1, detection coil W2, is swashed
Coil W3 and feedback coil W4 are encouraged, sampling coil W5, detection coil W6, excitation coil W7 and feedback coil are wound on iron core T2
W8；Excitation coil W3 is connected with excitation coil W7 differential concatenations, and excitation coil W3 other ends A and excitation coil W7 other ends A ' make
It is electrically connected with city for magnetic modulator exciting current input terminal；Sampling coil W1 is connected with sampling coil W5 differential concatenations, samples line
It encloses W1 other ends B and sampling coil W5 other ends B ' and is used as magnetic modulator input terminal, for inputting tested electric current；Detection coil W2
It is connected with detection coil W6 series aiding connections, detection coil W2 other ends C ' and detection coil W6 other ends C are defeated as magnetic modulator
Outlet；Feedback coil W4 is connected with feedback coil W8 series aiding connections, and the other end F's ' and feedback coil W8 of feedback coil W4 is another
One end F is as magnetic modulator feedback current input terminal；Shaping circuit input terminal is connected with magnetic modulator output end C；Shaping circuit
Output end is connected with the input terminal M of filter circuit；The input terminal N of filter circuit and the C ' connections of magnetic modulator output end；Feedback electricity
The input terminal on road is connect with filter circuit output end；Feedback circuit output is connected with the ends F of magnetic modulator feedback coil W8；Electricity
The F ' of one end and magnetic modulator feedback coil W4 hold connection, resistance R0 other ends ground connection after hindering R0 and voltmeter V parallel connections.
2. magnetic modulator current sensing means according to claim 1, which is characterized in that the shaping circuit is two-way steady
Depressor D.
3. magnetic modulator current sensing means according to claim 1 or 2, which is characterized in that the filter circuit is to have
Source low-pass filter circuit, including operational amplifier U1, resistance R1, resistance R2, capacitance C1 and capacitance C2, resistance R1 and resistance R2 strings
Connection connection, the other end of R1 are connect as filter circuit input terminal M, the R2 other end with operational amplifier U1 in-phase input ends；Fortune
The inverting input for calculating amplifier U1 is connect with the output end of operational amplifier U1；One end of capacitance C1 and resistance R1 and resistance R2
Tie point connects, and the capacitance C1 other ends are as filter circuit input terminal N；One end of capacitance C2 is same mutually defeated with operational amplifier U1's
Enter end connection, the other end is connect with filter circuit input terminal N；Output end of the output end of operational amplifier U1 as filter circuit
The output end Q of P, filter circuit are connect with input terminal N.
4. magnetic modulator current sensing means according to claim 1 or 2, which is characterized in that the feedback circuit includes
Operational amplifier U2, resistance R3, resistance R4, resistance R5 and capacitance C3；Resistance R3, capacitance C3 and resistance R4 are sequentially connected in series,
The resistance R3 other ends are connect as feedback circuit input terminal X, the other end of resistance R4 with the output end of operational amplifier U2, operation
The inverting input of amplifier U2 is connect with resistance R3, the junctions capacitance C3；One end of resistance R5 is same with operational amplifier U2's
Phase input terminal connects, the other end ground connection of resistance R5；Input terminal of the in-phase input end of operational amplifier U2 as feedback circuit
Y；The input terminal X of feedback circuit is connect with filter circuit output end Q, and the input terminal Y and filter circuit output end P of feedback circuit connect
It connects.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820362444.3U CN207866886U (en) | 2018-03-16 | 2018-03-16 | A kind of magnetic modulator current sensing means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820362444.3U CN207866886U (en) | 2018-03-16 | 2018-03-16 | A kind of magnetic modulator current sensing means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN207866886U true CN207866886U (en) | 2018-09-14 |
Family
ID=63456405
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201820362444.3U Expired - Fee Related CN207866886U (en) | 2018-03-16 | 2018-03-16 | A kind of magnetic modulator current sensing means |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN207866886U (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110297122A (en) * | 2019-06-19 | 2019-10-01 | 中国人民解放军海军工程大学 | Magnetic modulation sensor based on frequency model crosses range measurement method |
| CN110794191A (en) * | 2019-10-17 | 2020-02-14 | 天津大学 | Magnetic modulation type direct current leakage protection device for inhibiting zero drift influence |
| CN111208346A (en) * | 2020-01-19 | 2020-05-29 | 长沙天恒测控技术有限公司 | Small signal voltage measuring device and method |
| CN111665383A (en) * | 2020-05-22 | 2020-09-15 | 哈尔滨工业大学 | Full-digital fluxgate type current sensor |
-
2018
- 2018-03-16 CN CN201820362444.3U patent/CN207866886U/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110297122A (en) * | 2019-06-19 | 2019-10-01 | 中国人民解放军海军工程大学 | Magnetic modulation sensor based on frequency model crosses range measurement method |
| CN110297122B (en) * | 2019-06-19 | 2021-11-02 | 中国人民解放军海军工程大学 | Magnetic modulation sensor overrange measuring method based on frequency model |
| CN110794191A (en) * | 2019-10-17 | 2020-02-14 | 天津大学 | Magnetic modulation type direct current leakage protection device for inhibiting zero drift influence |
| CN111208346A (en) * | 2020-01-19 | 2020-05-29 | 长沙天恒测控技术有限公司 | Small signal voltage measuring device and method |
| CN111665383A (en) * | 2020-05-22 | 2020-09-15 | 哈尔滨工业大学 | Full-digital fluxgate type current sensor |
| CN111665383B (en) * | 2020-05-22 | 2022-06-21 | 哈尔滨工业大学 | Full-digital fluxgate type current sensor |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN207866886U (en) | A kind of magnetic modulator current sensing means | |
| CN111351535B (en) | Signal processing method of high-frequency sine wave excitation electromagnetic flowmeter | |
| CN102597755B (en) | Electrical tomography apparatus and method and current driver | |
| CN102288821B (en) | Measuring method, measuring device, measuring procedure and carrier for phase difference of three-phase circuit | |
| CN103376136A (en) | Electromagnetic flowmeter and self-diagnosing method of exciting circuit unit thereof | |
| CN111323632B (en) | AC/DC zero-flux fluxgate current sensor and program control configuration and calibration method thereof | |
| CN207263800U (en) | A kind of application DC offset voltage is in the device of AC sine wave signal source | |
| CN101900585A (en) | Narrowband filtering signal conditioning method and device of electromagnetic flowmeter | |
| CN105548710B (en) | A kind of enhanced autobalance bridge and its method for realizing impedance measurement | |
| CN112834815A (en) | Fluxgate digital current sensor based on pulse amplitude detection method | |
| CN201397122Y (en) | Linear displacement difference transformer signal modulate circuit | |
| CN107449949A (en) | Apply DC offset voltage in the device of AC sine wave signal source | |
| CN107228886B (en) | The measuring device and method of the conductivity Resistivity testing of water | |
| CN210629467U (en) | Front-end signal conditioning circuit of broadband VLF differential type magnetic rod receiving antenna | |
| CN204536516U (en) | A kind of high frequency low-intensity magnetic field circuitry for signal measurement of precision | |
| CN110456142A (en) | Magnetic modulation type DC leakage flow sensor | |
| CN111693753A (en) | Novel direct current measuring device | |
| CN204008813U (en) | A kind of magnetic modulation type current transformer | |
| CN103197153B (en) | A kind of capacitor and inductor parameter measurement circuit based on vector triangle and measuring method thereof | |
| JP4612282B2 (en) | Method for detecting the standard deviation of the measured value of magnetic induction type flow rate measuring method operating with excitation frequency | |
| CN204944423U (en) | A kind of capacitive MEMS sensor detection circuit | |
| CN102706383A (en) | Measurement device and method for differential capacitance type instrument | |
| CN108226279A (en) | Towards the special fluxgate detector of buried corrosion pipeline | |
| CN207571072U (en) | A kind of alkali concn tester | |
| CN103063928B (en) | System for testing earth grounding resistance, and digital coherent detection method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20180914 Termination date: 20190316 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |