CN106066425B - A kind of impedance measurement device and its method for realizing compensation for calibrating errors - Google Patents

A kind of impedance measurement device and its method for realizing compensation for calibrating errors Download PDF

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CN106066425B
CN106066425B CN201610616593.3A CN201610616593A CN106066425B CN 106066425 B CN106066425 B CN 106066425B CN 201610616593 A CN201610616593 A CN 201610616593A CN 106066425 B CN106066425 B CN 106066425B
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impedance
measurement
circuit
calibration
signal
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CN106066425A (en
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彭海军
张永坡
赵晖
戚瑞民
栗永强
王文廷
李雷
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CETC 41 Institute
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CETC 41 Institute
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/08Measuring resistance by measuring both voltage and current
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/005Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references

Abstract

The invention discloses a kind of impedance measurement device and its methods for realizing compensation for calibrating errors, belong to impedance measurement technique field, including measurement cable, measured material, autobalance bridge, frequency down circuit, A/D conversion circuit, FPGA, memory and CPU.The present invention carries out impedance measurement using autobalance bridge principle, has many advantages, such as that measurement accuracy is high, measuring speed is fast, impedance measurement range is wide;Using four ends to connection type, so that impedance measurement range is improved;By frequency down circuit, it converts high-frequency signal to the low frequency signal of fixed frequency, improves signal phase measurement accuracy;When being measured to measured piece, according to different measuring conditions, corresponding calibration value is selected to compensate impedance measurements, improve impedance measurement precision.

Description

A kind of impedance measurement device and its method for realizing compensation for calibrating errors
Technical field
The invention belongs to impedance measurement fields, and in particular to a kind of impedance measurement device and its side for realizing compensation for calibrating errors Method.
Background technique
Durings the research and development of electronic product, production, maintenance etc., require the resistance R to measured piece, inductance L, capacitor C, The parameters such as quality factor q, loss factor D measure, and measured piece can be component either circuit, the measurement of these parameters Its core is exactly to carry out the measurement of impedance, can extrapolate other parameters value according to impedance measurements.Currently, in impedance measurement device There are many kinds of the methods for realizing impedance measurement, there is bridge method, the resonance method, voltage-to-current method, RF voltage-to-current method, network analysis Method etc., every kind of method have respective advantage and disadvantage.The advantages of bridge method is that measurement accuracy is high, at low cost, but needs to adjust manually Save bridge balance, and measurement frequency narrow range.The resonance method can measure the measured piece with very high q value, the disadvantage is that measurement accuracy It is lower.Voltage-to-current method is suitable for probe type and tests occasion, and therefore, measurement frequency is limited by probe transformer.RF electricity Piezo-electric stream method has very high measurement frequency and range, cannot in this way but in low frequency, and higher cost. Although Network Analysis Method has very high measurement frequency, it is only applicable to the occasion that measured piece impedance is 50 Ω or so, therefore Impedance measurement range is very narrow, and higher cost.Therefore, in several impedance measurement methods of above-mentioned introduction, every kind of method is all There are respective advantage and disadvantage, be difficult to find a kind of impedance measurement method while having that measurement accuracy is high, measuring speed is fast, measurement frequency It high, the features such as impedance measurement range is wide, needs to select suitable impedance measurement side according to different application field and measurement request Method.
When carrying out impedance measurement, need according to different measurement requests, using different measurement cables and measured material, And cable and measured material itself are measured also comprising certain parasitic parameter, and parasitic parameter is also different, it is widely different, this Sample will generate certain influence to measured piece impedance measurements, so that measurement result deviates true value, especially in high frequency When measurement, influence of the parasitic parameter to measurement can be more obvious, may thus obtain full of prunes measurement result, seriously User is influenced to use.
Summary of the invention
For the above-mentioned technical problems in the prior art, the invention proposes a kind of impedance measurement device and its realizations The method of compensation for calibrating errors, design rationally, overcome the deficiencies in the prior art, have that measurement accuracy is high, measuring speed is fast, impedance is surveyed Measure the advantages that range is wide.
To achieve the goals above, the present invention adopts the following technical scheme:
A kind of impedance measurement device, including measurement cable, measured material, autobalance bridge, first choice switch, frequency reducing electricity Road, A/D conversion circuit, FPGA, memory and CPU;
The measurement cable connects interface mode using four ends with measured material;
The autobalance bridge includes driving source, zero cross detection circuit, modulation-demodulation circuit and range resistance;
The driving source is configurable for providing excitation source signal for measured piece;
The zero cross detection circuit is configurable for carrying out zero passage detection to error current and carries out signal processing;
The modulation-demodulation circuit is configurable for that the signal that zero cross detection circuit exports is modulated and is demodulated;
The range resistance, is configurable for the impedance ranges according to measured piece, selects suitable resistance gear;
The frequency down circuit is configurable for converting high-frequency signal measurement to the low frequency signal of fixed frequency;
The A/D conversion circuit, is configurable for that treated that analog signal is converted to digital letter by frequency down circuit Number;
The FPGA is configurable for the digital signal after converting and carries out data processing;
The CPU is configurable for carrying out impedance computation and analysis;
The memory is configurable for storing various calibration data;
When autobalance bridge reaches equilibrium state, two-way voltage signal initially enters frequency down circuit, and frequency down circuit will be high Frequency measuring signal is sent into A/D conversion circuit after being converted into the low frequency signal of fixed frequency, and A/D conversion circuit converts analog signal Data processing is carried out to be sent into FPGA after digital signal, FPGA is sent in CPU after being handled data, carries out impedometer It calculates and analyzes, and each calibration value is written in memory, and according to measuring condition, impedance value is compensated accordingly, is obtained Corresponding impedance compensation value.
Preferably, the frequency down circuit includes the second selection switch, third selection switch, multiplier, buffer, addition Device, filter, signal generator and signal processor;
Multiplier includes the first multiplier and the second multiplier;
Buffer includes the first buffer, the second buffer, third buffer and the 4th buffer;
Filter includes first filter and second filter;
Signal processor includes the first signal processor and second signal processor;
One of contact of second selection switch passes through input terminal of the connection to the first buffer, the first buffer Output end by first filter be connected to third selection switch a contact;
Another contact of second selection switch is respectively connected to the first multiplier and the second multiplier by route Input terminal;
Signal generator is respectively with the first signal processor and second signal processor by connection, at the first signal Reason device and second signal processor pass through the input terminal of connection to the first multiplier and the second multiplier respectively;
The output end of first multiplier is connected to the input terminal of the second buffer, and the output end of the second buffer, which is connected to, to be added One end of musical instruments used in a Buddhist or Taoist mass;
The output end of second multiplier is connected to the input terminal of third buffer, and the output end of third buffer, which is connected to, to be added The other end of musical instruments used in a Buddhist or Taoist mass;
The output end of adder is connected to the input terminal of the 4th buffer, and the output end of the 4th buffer passes through the second filtering Device is connected to another contact of third selection switch;
Second selection switch passes through route and first choice switch connection;
Third selection switch is connected by route with A/D converter.
In addition, the present invention is also mentioned that a kind of method for realizing impedance measurement compensation for calibrating errors, this method is using as described above A kind of impedance measurement device, includes the following steps:
Step 1: initial work is executed to measuring device;
Step 2: measured piece being disconnected, repeatedly open circuit calibration is executed to measuring device, and will open circuit calibration value write-in storage In device;
Step 3: by measured piece short circuit, repeatedly short circuit calibration being executed to measuring device, and short-circuit calibration value is written and is stored In device;
Step 4: according to measurement request, judging whether to execute load calibration to measuring device;
If: judging result is to execute load calibration to measuring device, thens follow the steps 5;
Or judging result is not execute load calibration, thens follow the steps 6;
Step 5: it is measured using known normal component as measured piece, multiple load calibration is executed to measuring device, and Load calibration value is written in memory;
Step 6: measured piece is connected in measuring device connection type by four ends;
Step 7: the adjusting including amplitude and phase is carried out to the feedback loop of autobalance bridge;
Step 8: judging that autobalance bridge is no and reach equilibrium state;
If: judging result is that autobalance bridge does not reach equilibrium state, thens follow the steps 7;
Or judging result is that autobalance bridge reaches equilibrium state, thens follow the steps 9;
Step 9: to voltage signalWithAmplitude and phase measure;
Step 10: according to formulaCalculate the impedance measurements of measured piece;In formula,For range electricity Resistance value,WithThe voltage signal values respectively measured;
Step 11: according to measuring condition, the impedance measurements of measured piece being compensated accordingly, are obtained impedance-compensated Value;
When not executing load calibration to measuring device, formula is pressed to impedance measurements It compensates, obtains the impedance compensation value of measured piece;In formula,For open a way calibration value,For short-circuit calibration value,For Impedance measurements;
When executing load calibration to measuring device, formula is pressed to impedance measurementsIt compensates, obtains the impedance compensation value of measured piece;In formula,For normal component measured value,For normal component true value,For open a way calibration value,For short-circuit calibration value,For Impedance measurements.
The principle of the present invention is:
Impedance measurement device of the present invention uses four port mode of standard, the respectively end Hc, the end Hp, the end Lp and the end Lc.Hc is Source, including AC signal and direct current signal are motivated, the high-end of measured piece DUT is applied to.Hp is the high-end voltage measurement of measured piece End, measures voltage signal Vx on measured piece.Lc is range resistance terminal, according to measured piece impedance value, selects corresponding amount Journey resistance gear, and voltage signal Vr on range resistance Rr is measured.Lp is error current end, and error current Id is equal to On measured piece on electric current Ix and range resistance electric current Ir difference.
Impedance measurement device carries out impedance measurement using autobalance bridge principle, when autobalance bridge does not reach equilibrium-like When state, the end Lp error current Id by the end Lp measurement 3 → zero cross detection circuit of cable → modulation-demodulation circuit → range resistance → The end Lc measures the end 4 → Lp of cable and measures 3 →... ... of cable, circuits sequentially, and forms feedback loop.In the negative anti-of autobalance bridge It presents in loop, amplitude adjusted and phase adjusted is carried out to error signal respectively, autobalance bridge is quickly and accurately reached To equilibrium state.
After autobalance bridge reaches equilibrium state, the error current Id at the end Lp is equal to zero, and therefore, measured piece low side is known as " virtual earth " point of autobalance bridge.At this moment electric current Ix is equal to electric current Ir on range resistance, therefore the impedance of measured piece on measured piece Value Zx are as follows:
(1)
In formula (1), Rr is range resistance value, and range resistance all using in high precision, the measuring resistance of Low Drift Temperature, For known quantity, Vx and Vr are to be measured, and Vx and Vr is vector signal, includes not only range value, further includes phase value, therefore, The impedance value Zx of measured piece can be calculated by formula (1).
The measurement cable and measured material of impedance measurement device can be by impedance measurement models using four ends to connection type It encloses and is increased to 1m Ω~10M Ω.It will measure the parasitic parameter that cable and measured material are included, it is equivalent at spurious impedance Zs and to post Raw admittance Yo two parts.In impedance measurement, due to using different measurement cable and measured material, so that parasitic parameter is not yet It is identical, it will impedance measurements to be directly affected, so that measured value deviates true value.Improve impedance measurement precision, it is necessary to Influence of the parasitic parameter that reduction measurement cable and measured material are included to measurement.Therefore, before impedance measurement, it is necessary to right Impedance measurement device executes calibration operation, including open circuit calibration, short circuit calibration and load calibration.
In usual measurement, such as to measurement accuracy require be not it is very high, using the measurement cable and measurement folder of standard Tool, measurement can be met and need by only carrying out open circuit calibration and short circuit calibration.When being measured to measured piece DUT, need According to open circuit calibration value and short-circuit calibration value, impedance measurements are compensated accordingly.
There are some measurement occasions, is such as needing higher measurement accuracy, the test cable using random length, Qi Tachang The test fixture etc. of family, influence of the parasitic parameter to measurement can not be effectively reduced by only carrying out open circuit calibration and short circuit calibration, Also need to be implemented load calibration.Load calibration is to obtain the measured value of normal component, and combine using normal component as measured piece Open circuit calibration value and short-circuit calibration value compensate impedance measurements when measuring to measured piece DUT accordingly, with Improve impedance measurement precision.
For open circuit set forth above calibration, short circuit calibration and load calibration these three calibration methods, when executing calibration, It needs to execute repeatedly calibration according to different measurement frequencies, measuring amplitude, measurement cable, measured material, normal component, will To calibration value all write-in memories in.When measuring to measured piece, according to measuring condition, different calibrations is selected Value, compensates impedance measurements, improves measurement accuracy.
Advantageous effects brought by the present invention:
The invention proposes a kind of impedance measurement device and its methods for realizing compensation for calibrating errors, compared with prior art, this Invention carries out impedance measurement using autobalance bridge principle, has measurement accuracy is high, measuring speed is fast, impedance measurement range is wide etc. Advantage;Impedance measurement device uses four ends to connection type, so that impedance measurement range is improved;It, will by frequency down circuit High-frequency signal is converted into the low frequency signal of fixed frequency, improves signal phase measurement accuracy;Before impedance measurement, need to be implemented out Road calibration, short circuit calibration and load calibration, and according to different measurement frequencies, measuring amplitude, measurement cable, measured material and mark Quasi- device, is repeatedly calibrated, and will be in calibration value all write-in memory;Impedance measurement device measures measured piece When, according to different measuring conditions, corresponding calibration value is selected to compensate impedance measurements, improves impedance measurement essence Degree.
Detailed description of the invention
Fig. 1 is a kind of hardware elementary diagram of impedance measurement device of the present invention.
Fig. 2 is the hardware elementary diagram of frequency down circuit in the present invention.
Fig. 3 is four ends in the present invention to the schematic diagram of connection type.
Fig. 4 is the schematic diagram of calibration of opening a way in the present invention.
Fig. 5 is the schematic diagram of short circuit calibration in the present invention.
Fig. 6 is the schematic diagram of impedance measurement and its realization compensation that the present invention executes when opening a way calibration and short circuit calibration.
Fig. 7 is the schematic diagram of load calibration in the present invention.
Specific embodiment
With reference to the accompanying drawing and specific embodiment invention is further described in detail:
Embodiment 1:
As shown in Figure 1, a kind of impedance measurement device, mainly includes measured piece DUT, measurement cable, measured material, puts down automatically The parts such as Heng Qiao, frequency down circuit, A/D converter, FPGA, memory and CPU, wherein autobalance bridge includes driving source, mistake again The parts such as zero detection circuit, modulation-demodulation circuit, range resistance.
Impedance measurement device uses four port mode of standard, the respectively end Hc, the end Hp, the end Lp and the end Lc.Hc is driving source End, including AC signal and direct current signal, wherein AC signal is realized using DDS, and direct current signal is converted using the D/A of 16bit Device is realized, AC signal and direct current is superimposed, after signal drive circuit is handled, is applied to the high-end of measured piece DUT.Hp For the high-end voltage measuring terminal of measured piece, voltage signal Vx on measured piece is measured.Lc is range resistance terminal, according to measured piece Impedance value selects corresponding range resistance gear, and measures to voltage signal Vr on range resistance Rr, and range resistance is complete Portion measurement accuracy is improved using high-precision, the measuring resistance of Low Drift Temperature.Lp is error current end, and error current Id is equal to quilt Survey the difference of electric current Ir on electric current Ix and range resistance on part.
Impedance measurement device carries out impedance measurement using autobalance bridge principle, does not reach equilibrium-like in autobalance bridge When state, the end Lp error current Id by the end Lp measurement 3 → zero cross detection circuit of cable → modulation-demodulation circuit → range resistance → The end Lc measures the end 4 → Lp of cable and measures 3 →... ... of cable, circuits sequentially, and forms feedback loop.In the negative anti-of autobalance bridge It presents in loop, amplitude adjusted and phase adjusted is carried out to error signal, autobalance bridge is enabled quickly and accurately to reach flat Weighing apparatus state.
After autobalance bridge reaches equilibrium state, voltage signal Vx and Vr are measured respectively.When switch S1 gets to A When, voltage signal Vx is measured;When switch S1 gets to B, voltage signal Vr is measured.It not only needs to measure voltage The amplitude of signal Vx and Vr, it is also necessary to the phase difference between them.Due to when measurement frequency is relatively high, being difficult to accurately survey The phase difference between two voltage signals is measured, therefore before A/D conversion circuit, devises a frequency down circuit, it first will be high Measurement frequency is converted to the low frequency signal of fixed frequency, then measures to signal, improves phase measurement accuracy.
Voltage signal Vx and Vr are sent into A/D conversion circuit after frequency down circuit, are converted to digital quantity, are re-fed into Data processing is carried out in FPGA, is finally sent to data in CPU by FPGA, carries out impedance computation and analysis, and CPU is also responsible for controlling Make entire impedance measurement device.In addition, FPGA is also connected with an external memory, for storing the various schools of impedance measurement device Quasi- data.
Embodiment 2:
On the basis of above-described embodiment 1, as shown in connection with fig. 2, a kind of impedance measurement device that the present invention introduces, to electricity When pressure signal Vx and Vr are measured, the amplitude of measurement voltage signal Vx and Vr is not only needed, it is also necessary to measurement voltage signal Vx Phase difference between Vr.With the raising of measurement frequency, it is ensured that impedance measurement precision, remain that accurately measure Vx and Phase difference between Vr, difficulty are also just increasing.In order to which measurement frequency is in high frequency, phase measurement accuracy is improved, impedance is surveyed It measures in device, before A/D conversion circuit, a frequency down circuit is designed, so that measurement frequency in high frequency, is first converted to fixation The low frequency signal of frequency, then signal is measured, phase measurement accuracy is improved, impedance measurement precision is finally also improved.
As shown in connection with fig. 2,2 tunnel amplitudes of DDS3 signal generating circuit generation are equal, frequency is equal, phase phase difference fixes 90 ° Sinusoidal reference signal V0 and V90, and the frequency of reference signal V0 and V90 be equal to measurement frequency+5kHz.It is selected in turn by switch S1 Voltage signal Vx and Vr to be measured is selected, different circuits is selected according to the size of measurement frequency into frequency down circuit.When measurement frequency When rate f≤32kHz, switch S11 and switch S12 get to A point, measured signal after buffer N12 and filter 1 are handled, It is directly sent in A/D conversion circuit, needs not move through down conversion process;As measurement frequency f > 32kHz, switch S11 and switch S12 gets to B point, needs that measured signal is sent to the input terminal of multiplier 1 and multiplier 2 by down conversion process, respectively and joins Signal V0 to be examined to be multiplied with V90, the output of multiplier 1 is sent to the one of input terminal of adder 1 after buffer N10 processing, The output of multiplier 2 is sent to another input terminal of adder 1, the output signal of adder 1 after buffer N11 processing After buffer N13 and filter 2 are handled, the low frequency signal for being just fixed 5kHz by measured signal frequency conversion, by this Low frequency 5kHz signal is sent in A/D conversion circuit, is converted into digital quantity, for impedance computation use.High-frequency signal measurement passes through After frequency down circuit processing, signal phase measurement accuracy can be significantly improved, i.e. raising impedance measurement precision.
Embodiment 3:
On the basis of above-described embodiment 1, as shown in connection with fig. 3, a kind of impedance measurement device that the present invention introduces, using four To connection type, impedance measurement range can achieve 1m Ω~10M Ω at end.
When impedance measuring equipment and measurement cable are attached, measurement cable 1 is connected with the end Hc, and needing will measurement electricity The shielding ground of cable 1 is connected with the ground at the end Hc with conducting wire X11.Similarly, measurement cable 2 is connected with the end Hp, and needing will measurement The shielding ground of cable 2 is connected with the ground at the end Hp with conducting wire X12;Measurement cable 3 is connected with the end Lp, and needs that cable will be measured 3 shielding ground is connected with the ground at the end Lp with conducting wire X13;Measurement cable 4 is connected with the end Lc, and needs that cable 4 will be measured Shielding ground is connected with the ground at the end Lc with conducting wire X14.
When measuring cable and measured material and being attached, measurement cable 1 is connected with the end Hc of measured material, and need by The shielding of cable 1 ground is measured to be connected with the ground at the end Hc with conducting wire X21.Similarly, the end the Hp phase of cable 2 and measured material is measured Even, and with needing to measure the shielding of cable 2 it is connected with the ground at the end Hp with conducting wire X22;Measure cable 3 and measured material The end Lp is connected, and is connected with the ground at the end Lp with conducting wire X23 with needing to measure the shielding of cable 3;Measure cable 4 and measurement The end Lc of fixture is connected, and is connected with the ground at the end Lc with conducting wire X24 with needing to measure the shielding of cable 4.
Inside measured material, the end Hc is connected with the end Hp, the high-end of autobalance bridge is formed, by the end Lp and the end Lc phase Even, the low side of autobalance bridge is formed, and needs for be connected with the ground at the end Hp with conducting wire X31 on the ground at the end Hc;The ground at the end Hp It is connected with the ground at the end Lp with conducting wire X32;The ground at the end Lp is connected with the ground at the end Lc with conducting wire X33.
Above-mentioned four end is to connection type used by the measurement cable and measured material of impedance measurement device, compared to other Connection type can significantly improve impedance measurement range.
Embodiment 4:
On the basis of above-described embodiment 1, in conjunction with shown in Fig. 4, Fig. 5, Fig. 6, invention describes a kind of execution open circuit schools Quasi- and short circuit calibration impedance measurement and its method for realizing compensation.
As shown in connection with fig. 4, the parasitic parameter that the measurement cable of impedance measurement device of the invention and measured material are included, Can be equivalent at spurious impedance Zs and parasitic admittance Yo two parts, wherein spurious impedance Zs includes dead resistance Rs and parasitic inductance Ls, i.e.,;Parasitic admittance Yo includes parasitic conductance Go and parasitic capacitance Co, i.e.,.Into When row impedance measurement, due to using different measurement cable and measured material, so that parasitic parameter is not also identical, it will direct shadow Impedance measurements are rung, so that measured value deviates true value, especially in high frequency measurement, influence meeting of the parasitic parameter to measurement It is more obvious, it may thus obtain full of prunes measurement result, seriously affect user's use.Improve impedance measurement essence Degree, it is necessary to influence of the parasitic parameter that reduction measures cable and measured material is included to measurement.Therefore, in impedance measurement Before, it is necessary to calibration operation, including open circuit calibration and short circuit calibration are executed to impedance measurement device.
As shown in connection with fig. 4, open circuit calibration is in measured piece open circuit, to the measurement cable and test clip of impedance measurement device Have included parasitic parameter to measure, at this point, spurious impedance Zs is much smaller than parasitic admittance 1/Yo, i.e.,, therefore, can Ignored with the influence by spurious impedance Zs to impedance measurement, equivalent parasitic parameter when measured piece is opened a way is
As shown in connection with fig. 5, short circuit calibration is in measured piece short circuit, to the measurement cable and test clip of impedance measurement device Have included parasitic parameter to measure, at this point, parasitism admittance 1/Yo is much smaller than spurious impedance Zs, i.e.,, therefore, Can the influence by parasitic admittance Yo to impedance measurement ignore, equivalent parasitic parameter when measured piece short circuit is
As shown in connection with fig. 6, in general measure, such as to measurement accuracy require be not it is very high, using the measurement of standard Cable and measured material etc., measurement needs can be met by only carrying out open circuit calibration and short circuit calibration.It is carried out when to measured piece DUT When measurement, need to compensate impedance measurements according to open circuit calibration value and short-circuit calibration value, that is, remove measurement cable and survey Influence of the parasitic parameter of fixture to measurement is measured, the impedance measurements Zxm of measured piece can be expressed from the next:
(2)
From formula (2) it can be concluded that the impedance Z dut of measured piece DUT are as follows:
(3)
It can be seen that the impedance Z dut of measured piece DUT from formula (3) and be not equal to measured value Zxm, if before measuring not Open circuit calibration and short-circuit calibration operation are executed, and impedance measurements are compensated accordingly, it will directly affects impedance measurement Precision.
Both calibration methods are calibrated for open circuit set forth above calibration and short circuit, when executing calibration, need basis Different measurement frequency, measuring amplitude, measurement cable, measured material, execute repeatedly calibration, obtained calibration data are all write Enter in memory.When measuring to measured piece, according to measuring condition, different calibration data is selected, to impedance measurements It compensates, improves measurement accuracy.
Embodiment 5:
On the basis of above-described embodiment 1 and embodiment 4, as shown in connection with fig. 7, invention describes one kind to open in addition to executing Road calibration and short circuit calibration are outer, the also impedance measurement of execution load calibration and its method for realizing compensation.
In some measurement occasions, higher measurement accuracy, the test cable using random length, other producers are such as needed Test fixture etc., impedance measurement device, which only carries out open circuit calibration and short circuit calibration, can not effectively reduce parasitic parameter to survey The influence of amount, it is also necessary to execute load calibration.Load calibration is measured using known normal component as measured piece, as negative Calibration value is carried, and load calibration value is written in memory.
As shown in connection with fig. 7, test cable, the test fixture etc. between impedance measuring equipment and measured piece DUT are partially seen At unknown four port network, this unknown four port network can be expressed from the next:
(4)
It can be obtained by formula (4):
(5)
When executing load calibration, measured piece selects known normal component Zstd, and normal component measured value is Zsm, can obtain:
(6);
(7);
Combinatorial formula (5), (6), (7) can obtain:
(8)
When executing open circuit calibration, I2=0,, i.e.,
When executing short circuit calibration, V2=0,, i.e.,
C and B value is substituted into formula (8), can be obtained:
(9)
When carrying out impedance measurement to measured piece DUT, can be obtained according to formula (9):
(10)
Combinatorial formula (9) and (10) can obtain:
(11);
After impedance measurement device executes open circuit calibration, short circuit calibration and load calibration respectively, measured piece DUT is surveyed When amount, impedance measurements need to be compensated accordingly by formula (11), improve impedance measurement precision.
For open circuit set forth above calibration, short circuit calibration and load calibration these three calibration methods, when executing calibration, It needs to be executed multiple according to different measurement frequencies, measuring amplitude, measurement cable, measured material and different normal components Calibration, will be in obtained calibration data all write-in memory.When being measured to measured piece, according to measuring condition, selection Different calibration data, compensates impedance measurements, improves measurement accuracy.
Embodiment 6:
On the basis of above-described embodiment 1~5, invention describes a kind of impedance measurement device realize impedance measurement and its The method of compensation for calibrating errors, specific execution process are as shown below:
Step 1: executing the initial work of impedance measurement device, mainly include four ends to connection, the generation of DDS signal, width Degree is adjusted, filter circuit selects, integrating capacitor selects, switch state selects etc.;
Step 2: measured piece being disconnected, executes the open circuit calibration of impedance measurement device, and will open circuit calibration value write-in storage In device;
Step 3: by measured piece short circuit, executing the short circuit calibration of impedance measurement device, and short-circuit calibration value is written and is stored In device;
Step 4: according to measurement request, deciding whether the load calibration for executing impedance measurement device.Situation 1: it is generally surveying In the case of amount, such as to measurement accuracy require be not it is very high, in this case can be with using the measurement cable and measured material of standard Load calibration is not executed, i.e., does not execute the step;Situation 2: in some measurement occasions, higher measurement accuracy, use are such as needed The test cable of random length, test fixture of other producers etc., just need to be implemented load calibration in this case.Load school Standard is measured using known normal component as measured piece, and memory is written as load calibration value, and by load calibration value In.
Impedance measurement device needs are repeatedly calibrated according to different measurement frequencies, measuring amplitude, normal component, are repeated Step 2~step 4 is executed, and will be in calibration value all write-in memory;
Step 5: measured piece DUT is connected in impedance measurement device connection type by four ends;
Step 6: autobalance bridge is adjusted, exactly the feedback loop of autobalance bridge is adjusted, including Amplitude adjusted and phase adjusted;
Step 7: judging that autobalance bridge is no and reach equilibrium state.If not reaching equilibrium state, it re-execute the steps 6;If reaching equilibrium state, execute down;
Step 8: executing the measurement of voltage signal Vx and Vr.When switch S1 gets to A, voltage signal Vx is measured; When switch S1 gets to B, voltage signal Vr is measured.Not only need the amplitude of measurement voltage signal Vx and Vr, it is also necessary to Phase difference between measurement voltage signal Vx and Vr;
Step 9: according to the amplitude measurements and phase measurement of voltage signal Vx and Vr, measured piece being carried out in CPU Impedance computation obtains the impedance measurements of measured piece;
Step 10: according to measuring condition, measured piece impedance measurements being compensated accordingly, show that measured piece impedance is mended Repay value.When measuring condition meets the situation 1 in step 4, impedance measurements are compensated by formula (3);Work as measuring condition When meeting the situation 2 in step 4, impedance measurements are compensated by formula (11);
Step 11: according to measured piece impedance compensation value, further calculating and analyze in CPU, extrapolate its of measured piece Its parameter value.
The present invention using autobalance bridge principle carry out impedance measurement, including measured piece, measurement cable, measured material, from Dynamic balancing bridge, frequency down circuit, A/D converter, FPGA, memory and CPU, have that measurement accuracy is high, measuring speed is fast, impedance is surveyed Measure the features such as range is wide;Impedance measurement device uses four ends to connection type, so that impedance measurement range is improved;Pass through drop Frequency circuit converts high-frequency signal to the low frequency signal of fixed frequency, improves signal phase measurement accuracy;Before impedance measurement, Calibration of opening a way, short circuit calibration and load calibration are needed to be implemented, and according to different measurement frequencies, measuring amplitude, measurement cable, survey Fixture and normal component are measured, is repeatedly calibrated, and will be in calibration value all write-in memory;Impedance measurement device is to measured piece When measuring, according to different measuring conditions, corresponding calibration value is selected to compensate impedance measurements, improves impedance and survey Accuracy of measurement.
Certainly, the above description is not a limitation of the present invention, and the present invention is also not limited to the example above, this technology neck The variations, modifications, additions or substitutions that the technical staff in domain is made within the essential scope of the present invention also should belong to of the invention Protection scope.

Claims (2)

1. a kind of impedance measurement device, it is characterised in that: opened including measurement cable, measured material, autobalance bridge, first choice Pass, frequency down circuit, A/D conversion circuit, FPGA, memory and CPU;
The measurement cable connects interface mode using four ends with measured material;
The autobalance bridge includes driving source, zero cross detection circuit, modulation-demodulation circuit and range resistance;
The driving source is configurable for providing excitation source signal for measured piece;
The zero cross detection circuit is configurable for carrying out zero passage detection to error current and carries out signal processing;
The modulation-demodulation circuit is configurable for that the signal that zero cross detection circuit exports is modulated and is demodulated;
The range resistance, is configurable for the impedance ranges according to measured piece, selects suitable resistance gear;
The frequency down circuit is configurable for converting high-frequency signal measurement to the low frequency signal of fixed frequency;
The A/D conversion circuit, is configurable for that treated that analog signal is converted to digital signal by frequency down circuit;
The FPGA is configurable for the digital signal after converting and carries out data processing;
The CPU is configurable for carrying out impedance computation and analysis;
The memory is configurable for storing various calibration data;
When autobalance bridge reaches equilibrium state, two-way voltage signal initially enters frequency down circuit, and frequency down circuit surveys high frequency Amount signal is sent into A/D conversion circuit after being converted into the low frequency signal of fixed frequency, and A/D conversion circuit converts analog signals into number After word signal be sent into FPGA in carry out data processing, FPGA is sent in CPU after being handled data, carry out impedance computation and Analysis, and each calibration value is written in memory, and according to measuring condition, impedance value is compensated accordingly, it obtains corresponding Impedance compensation value;
The frequency down circuit includes the second selection switch, third selection switch, multiplier, buffer, adder, filter, letter Number generator and signal processor;
Multiplier includes the first multiplier and the second multiplier;
Buffer includes the first buffer, the second buffer, third buffer and the 4th buffer;
Filter includes first filter and second filter;
Signal processor includes the first signal processor and second signal processor;
Second selection switch one of contact by connection to the first buffer input terminal, the first buffer it is defeated Outlet is connected to a contact of third selection switch by first filter;
Another contact of second selection switch is respectively connected to the input of the first multiplier and the second multiplier by route End;
Signal generator passes through connection, the first signal processor with the first signal processor and second signal processor respectively Pass through the input terminal of connection to the first multiplier and the second multiplier respectively with second signal processor;
The output end of first multiplier is connected to the input terminal of the second buffer, and the output end of the second buffer is connected to adder One end;
The output end of second multiplier is connected to the input terminal of third buffer, and the output end of third buffer is connected to adder The other end;
The output end of adder is connected to the input terminal of the 4th buffer, and the output end of the 4th buffer is connected by second filter It is connected to another contact of third selection switch;
Second selection switch passes through route and first choice switch connection;
Third selection switch is connected by route with A/D converter.
2. a kind of method that impedance measurement device realizes compensation for calibrating errors, it is characterised in that: using as described in claim 1 a kind of Impedance measurement device includes the following steps:
Step 1: initial work is executed to measuring device;
Step 2: measured piece being disconnected, repeatedly open circuit calibration is executed to measuring device, and will be in open circuit calibration value write-in memory;
Step 3: by measured piece short circuit, repeatedly short circuit calibration being executed to measuring device, and short-circuit calibration value is written in memory;
Step 4: according to measurement request, judging whether to execute load calibration to measuring device;
If: judging result is to execute load calibration to measuring device, thens follow the steps 5;
Or judging result is not execute load calibration, thens follow the steps 6;
Step 5: being measured using known normal component as measured piece, multiple load calibration is executed to measuring device, and will bear It carries in calibration value write-in memory;
Step 6: measured piece is connected in measuring device connection type by four ends;
Step 7: the adjusting including amplitude and phase is carried out to the feedback loop of autobalance bridge;
Step 8: judging that autobalance bridge is no and reach equilibrium state;
If: judging result is that autobalance bridge does not reach equilibrium state, thens follow the steps 7;
Or judging result is that autobalance bridge reaches equilibrium state, thens follow the steps 9;
Step 9: to voltage signal VxAnd VrAmplitude and phase measure;
Step 10: according to formulaCalculate the impedance measurements Z of measured piecexm;In formula, RrFor range resistance value, VxAnd VrThe voltage signal values respectively measured;
Step 11: according to measuring condition, the impedance measurements of measured piece being compensated accordingly, obtain impedance compensation value;
When not executing load calibration to measuring device, formula is pressed to impedance measurementsIt compensates, Obtain the impedance compensation value Z of measured piecedut;In formula, YoFor calibration value of opening a way, ZsFor short-circuit calibration value, ZxmFor impedance measurements;
When executing load calibration to measuring device, formula is pressed to impedance measurementsInto Row compensation, obtains the impedance compensation value Z of measured piecedut;In formula, ZsmFor normal component measured value, ZstdFor normal component true value, ZOFor calibration value of opening a way, ZsFor short-circuit calibration value, ZxmFor impedance measurements.
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