CN1150248A

CN1150248A - On-line measuring method and apparatus for resistance, capacity and inductance

Info

Publication number: CN1150248A
Application number: CN 95117908
Authority: CN
Inventors: 潘明海
Original assignee: No014 Center China Aeronautics Industry Corp
Current assignee: No014 Center China Aeronautics Industry Corp
Priority date: 1995-10-30
Filing date: 1995-10-30
Publication date: 1997-05-21

Abstract

An improved on-line measurement method for electric resistors, capacitors and inductor features that equipotential isolation method is used to isolate devices to be measured from each other and a single-chip computer system is used to control the measuring process and to calculate and display result. Its advantages include wide measuring range and high accuracy.

Description

Resistance, electric capacity, inductance On-line Measuring Method and device

The invention belongs to the electron device measurement technology, relate to the measuring method of online resistance, electric capacity, inductance and the improvement of device.

It is a very useful technology that components and parts on the wiring board are carried out on-line measurement.At being used in electronics industry by computer-controlled special measurement device of a kind of specific circuit plate, but this device is complicated, and does not have versatility." electrical measurement and instrument " 1993 the 5th phase 27-30 pages or leaves disclose a kind of " intelligent online multimeter ", only show energy measurement 2M with interior resistance through testing this, online electric capacity, the inductance of energy measurement not, and this kind multimeter does not drop into commercial production yet so far.And the instrument that does not also have both at home and abroad so far to measure discrete elements such as online resistance, electric capacity, inductance drops into actual the use.The gordian technique that realizes on-line measurement discrete component parameter is element being measured to be carried out electricity isolate.All adopt traditional electric partition method now both at home and abroad, referring to " Introduction to In-Circuit Testing " Part2 and " electrical measurement and instrument " 1988.11. articles such as " on-line testing technology and principles thereof ".Traditional electric partition method referring to attached Fig. 1 and 2, is that the virtual earth principle of utilization operational amplifier realizes.Detected element Z _XWith connected other elements always can equivalence be one by Z _X, Z ₁And Z ₂The triangular network of forming, Z ₁, Z ₂Be equiva lent impedance.Detected element inserts the backfeed loop of operational amplifier among Fig. 1, and measuring resistance inserts inverting input.Because operational amplifier inverting input potential pole makes Z near the earth potential of in-phase input end ₁On almost do not have electric current, therefore can calculate Z according to following formula _XValue:

Z_{X} = - {\dot{V}}_{o} / {\dot{V}}_{i}

Detected element inserts input circuit in Fig. 2, and measuring resistance inserts backfeed loop, then

Z_{X} = - {\dot{V}}_{i} / {\dot{V}}_{o}

Above

With

The plural form of the input of expression operational amplifier, output signal.Because

With R be known quantity,

Can measure, therefore can calculate Z _X, and then obtain the numerical value of resistance, electric capacity or inductance.

The shortcoming of traditional electric partition method is:

The first, poor stability.If detected element is electric capacity or inductance, it will constitute a phase shift link together with measuring resistance R, be easy to produce self-sustained oscillation.Therefore traditional electric partition method is difficult to the measurement of realization to electric capacity and inductance.Also be difficult to realize the measurement of high value and low resistance during measuring resistance.

The second, precision is low.Measuring accuracy is subjected to the Effect on Performance of operational amplifier own to be difficult to improve.And the circuit shown in Fig. 1 or 2 is very responsive to the waveform distortion and the noise of signal source, and output signal-to-noise ratio is descended.

Because above-mentioned fatal shortcoming is arranged, traditional electric partition method is unsuitable for directly carrying out the on-line measurement of discrete component, does not therefore still have actual product to put on market so far.

The purpose of this invention is to provide a kind ofly, be called the equipotential isolation method carry out the new method that electricity is isolated in kind of thread elements; A kind of measurement mechanism of measuring the method for online resistance, electric capacity, inductance and using the discrete resistance of said method on-line measurement, electric capacity, inductance is provided.

Technical scheme of the present invention is:

A kind of equipotential partition method is used for that online resistance, electric capacity, inductance element are carried out equipotential and isolates, and it is characterized in that (1), the output terminal of an operational amplifier directly is connected with its inverting input forms a voltage follower; (2), with the end of benchmark precision resistance R and segregate at kind of thread elements Z _xAn end connect the other end of benchmark precision resistance R and signal source V by lead _iPerhaps connect, segregate at kind of thread elements Z _xThe other end by lead with ground or signal source V _iConnect benchmark precision resistance R and segregate at kind of thread elements Z _xAn end that connects is connected with the in-phase input end of operational amplifier simultaneously; (3), isolating points C all on the output terminal of operational amplifier and the wiring board is connected, definite method of isolating points C is: every in the circuit board and segregate at kind of thread elements Z by lead _xNear signal source V _iThe resistance that links to each other of an end A, electric capacity, the other end of inductance element be isolation end C.

A kind of use as above-mentioned equipotential isolation method is isolated in the method that line resistance, electric capacity, inductance element are measured is characterized in that,

(1), measured element is realized that equipotential isolates, its method is: first, the output terminal of an operational amplifier directly is connected with its inverting input, forms a voltage follower with the equipotential isolation method; Second, with an end and the measured element Z of benchmark precision resistance R _xAn end connect the other end of benchmark precision resistance R and signal source V by lead _iPerhaps connect measured element Z _xThe other end by lead with ground or signal source V _iConnect benchmark precision resistance R and measured element Z _xAn end that connects is connected with the in-phase input end of operational amplifier simultaneously, and third, isolating points C all on the output terminal of operational amplifier and the wiring board is connected by lead, definite method of isolating points C is: every in the circuit board and measured element Z _xNear signal source V _iThe resistance that links to each other of an end A, electric capacity, the other end of inductance element be isolation end C.(2), measure signal voltage on the benchmark precision resistance R respectively

Complex values and measured element Z _xOn signal voltage

Complex values, then according to formula

Z_{X} = R * ({\dot{V}}_{Z} / {\dot{V}}_{R})

Calculate the value of measured element.

A kind of device that uses above-mentioned measuring method to measure online resistance, electric capacity, inductance element comprises it is characterized in that the Single Chip Microcomputer (SCM) system 12 of, a control survey process 10 that form by single-chip microcomputer 8, display 9 and keyboard and calculating, demonstration measurement result,

(1), have an equipotential buffer circuit that online measured element is carried out equipotential to isolate, this circuit has an operational amplifier 2, its output terminal is connected with inverting input, the formation voltage follower has a signal voltage source V _i11, benchmark precision resistance R is connected signal voltage source V _iAnd between the in-phase input end of operational amplifier 2, the slotted line 13 of being drawn by the in-phase input end of operational amplifier 2 connects an end of detected element when measuring, the slotted line 15 of being drawn by the ground of measurement mechanism connects the other end of detected element when measuring, the many shielding wires of being drawn by the output terminal of operational amplifier connect all isolating points through determining on the wiring board at detected element place when measuring

(2), an integrated analog switch 3 is arranged, under the control of Single Chip Microcomputer (SCM) system 12, finish the voltage on the measuring basis precision resistance R With the voltage on the detected element

The time contact switch,

(3), a differential amplifier 4 is arranged, finish the voltage on the benchmark precision resistance R

The perhaps voltage on the detected element Computing and amplification,

(4), there is the output valve of 5 pairs of differential amplifiers 4 of a programmable amplifier to amplify, its enlargement factor can be controlled by Single Chip Microcomputer (SCM) system, size according to input signal amplitude is selected suitable enlargement factor, its output signal is handled by Single Chip Microcomputer (SCM) system after the A/D conversion, obtains the value of detected element.

Advantage of the present invention is: the equipotential isolation method does not insert detected element in the loop of operational amplifier, and it is subjected to the influence of the parameter of operational amplifier own minimum, so good stability, and measuring current voltage can improve, and can not produce self-sustained oscillation.Online resistance of the present invention, electric capacity, inductance measurement method and apparatus can be measured above-mentioned numerical value in kind of thread elements exactly, the measuring accuracy height.Table 1 provides when using measurement mechanism of the present invention to measure online resistance and uses the contrast of digital multimeter measured value.When using digital multimeter to measure is the numerical value of measured resistance being pulled down off-line measurement from wiring board.Table 2 is to use the situation of this measurement device electric capacity.

The table 1 resistance measurement value table of comparisons

Sequence number	Nominal value	Apparatus of the present invention on-line measurement value	DT9201 digital watch off-line measurement value
Sequence number	Nominal value		DT9201 digital watch off-line measurement value	??1	0.2Ω	????0.199Ω	???????0.6Ω
??2	1Ω	??????1Ω	???????1.4Ω	??1	0.2Ω	????0.199Ω	???????0.6Ω
??2	1Ω	??????1Ω	???????1.4Ω	??3	5.1KΩ	????5.07KΩ	???????5.08KΩ
??4	10KΩ	????9.98KΩ	???????10.1KΩ	??3	5.1KΩ	????5.07KΩ	???????5.08KΩ
??4	10KΩ	????9.98KΩ	???????10.1KΩ	??5	200KΩ	?????198KΩ	????????201KΩ

Table 2 measurement capacitance

Sequence number	Nominal value	Apparatus of the present invention on-line measurement value
Sequence number	Nominal value		??1	????100PF	??????94PF
??2	????0.1μF	????0.098μF	??1	????100PF	??????94PF
??2	????0.1μF	????0.098μF	??3	????10μF	??????9.8μF
??4	????100μF	???????94μF	??3	????10μF	??????9.8μF
??4	????100μF	???????94μF	??5	????1000μF	??????960μF
??6	????2200μF	?????2150μF	??5	????1000μF	??????960μF
??6	????2200μF	?????2150μF	??7	????3300μF	?????3205μF

Measurement mechanism measurement range of the present invention is wide, measuring accuracy is high, automatic conversioning broad, easy to use.Table 3 provides the measurement range and the precision of on-line measurement device of the present invention.

Table 3 measurement range and precision

The detected element kind	Measurement range	Measuring accuracy
The detected element kind	Measurement range	Measuring accuracy	Resistance	0.1Ω-10MΩ	????±0.5％
Electric capacity	10PF-10000μF	????±2％	Resistance	0.1Ω-10MΩ	????±0.5％
Electric capacity	10PF-10000μF	????±2％	Inductance	10μH-100H	????±3％

Description of drawings.Fig. 1 is traditional electrical isolation method measuring principle figure.Fig. 2 is the traditional electrical isolation method principle of another kind of connection.Fig. 3 is an equipotential isolation method principle of the present invention.Fig. 4 is the equipotential isolation method principle of another kind of connection.Fig. 5 determines the isolating points synoptic diagram.Fig. 6 also is a synoptic diagram of determining isolating points.Fig. 7 is the synoptic diagram of measuring method of the present invention and measurement mechanism.Fig. 8 is the schematic diagram of measurement mechanism of the present invention.Fig. 9 is the schematic diagram of measurement mechanism of the present invention.Figure 10 is a measurement mechanism main program block diagram of the present invention.The present invention is described in detail below in conjunction with accompanying drawing.

Fig. 1 and Fig. 2 are traditional electric isolation methods.Wherein the backfeed loop of operational amplifier 1 is connected to detected element or measuring resistance, makes its end of oppisite phase be close to earth potential, so at Z _XIn marking current with flow through the approximately equal of R.Realization is to the isolation of detected element.

Fig. 3 and Fig. 4 are the principles that equipotential of the present invention is isolated.Among Fig. 3, detected element Z _XBe connected between the in-phase end and ground of amplifier 2, reference resistance R is connected on signal source V _iAnd between the amplifier in-phase end.Amplifier 2 its inverting inputs of output termination become a voltage follower.The current potential of its output terminal equals the in-phase end current potential all the time, therefore at equiva lent impedance Z ₁On do not have marking current, promptly flow through Z _XMarking current with flow through equating of R, realize Z _XEquipotential isolate.Will be by Z _X, Z ₁, Z ₂The summit of the triangular network of forming represents that with alphabetical A, B, C A, B are the two ends of detected element, and C is equiva lent impedance Z ₁, Z ₂Intersection point, be referred to as isolating points.Have the different isolating points of quantity for different detected element in the circuit board, need determine according to the connection situation of detected element in circuit.Z among Fig. 4 _XExchanged the position with R, identical with Fig. 3 on the principle that equipotential is isolated.During element on isolating a wiring board, need the equipotential buffer circuit be connected with this wiring board with lead.Have two kinds to connect lead, a kind of is two slotted lines, referring to Fig. 7, slotted line 13 is drawn by the in-phase end of amplifier 2, one end of the detected element on the connection line plate, slotted line 15 is drawn by the ground of equipotential buffer circuit, the other end of detected element on the connection line plate; Second kind of connection lead is called shielding wire, and this may be a multiple conducting wires, is drawn predetermined all isolating points C on the connection line plate by the output terminal of amplifier 2.For simplicity, the earth-free slotted line of that root is called slotted line A, that root slotted line of ground connection is called slotted line B.Fig. 5 and circuit shown in Figure 6 are elective circuit, and purpose is the definite method for isolating points on illustrating when the actual measurement wiring board.In general, to connect the other end of the element that the end of slotted line A is connected all be isolating points C for every and detected element.Enumerate the example of in Fig. 5 and Fig. 6, measuring several elements below.The connection situation of slotted line sees Table 4.

Table 4 slotted line connects

Detected element	Slotted line A tie point	Slotted line B tie point	The shielding wire tie point
Detected element	Slotted line A tie point	Slotted line B tie point	The shielding wire tie point	????R ₁₀	????P ₁	????P ₀	??????P ₂
????R ₁₁	????P ₁	????P ₂	??????P ₀	????R ₁₀	????P ₁	????P ₀	??????P ₂
????R ₁₁	????P ₁	????P ₂	??????P ₀	????R ₁₂	????P ₃	????P ₄	??????P ₅
????R ₁₃	????P ₃	????P ₅	??????P ₄	????R ₁₂	????P ₃	????P ₄	??????P ₅
????R ₁₃	????P ₃	????P ₅	??????P ₄	????R ₁₄	????P ₇	????P ₆	????P ₈、P ₉
????C	????P ₇	????P ₉	????P ₆、P ₈	????R ₁₄	????P ₇	????P ₆	????P ₈、P ₉

Fig. 7 is the schematic diagram and the embodiment of On-line Measuring Method of the present invention and device, and Fig. 8 is the embodiment of measurement mechanism.Form the equipotential buffer circuit by amplifier 2 and reference resistance R.Signal source 11 provides signal voltage V _iThe detected element R that slotted line 13 connects on the printed panel _XAn end A, slotted line 15 connects R _XOther end B, shielding wire 14 connects isolating points C.Because C point current potential equals the current potential that A is ordered, on R*, do not have marking current like this, realized R _XIsolation.Signal source can adopt direct current or AC signal, adopts ac signal which usually.Can use complex representation AC signal voltage, the corresponding active component of its real part, corresponding electric capacity of imaginary part or inductive part.Can adopt a sine signal source that frequency is provided is the sinusoidal ac signal of 100Hz-1000Hz.Can constitute signal source with integrated circuit (IC) L8038, also can adopt other circuit.Requiring the output amplitude of signal voltage is 3-6V, and degree of distortion is less than 0.5%.

After adopting the equipotential isolation method that detected element is isolated,, be equivalent to one by detected element Z for signal source 11 _XSeries circuit with reference resistance R composition.As long as measure Z _XWith the signal voltage on the R, just can obtain Z _XRelation with R.Because R is a known quantity, can obtain Z in view of the above _XValue.Therefore the step of measuring is: measure the signal voltage on the benchmark precision resistance R respectively Complex values and measured element Z _XOn signal voltage

Complex values, then according to formula

Z_{X} = R * ({\dot{V}}_{Z} / {\dot{V}}_{R})

Calculate the value of measured element.When actual measurement, as long as measure

With Two component of voltages in any orthogonal coordinate system get final product, and needn't consider initial phase angle.Adopt the signal voltage on the following method measuring basis precision resistance R in the actual measurement With measured element Z _xOn signal voltage

And the value of definite detected element.

At first, measure a certain moment

On instantaneous voltage V ₁And synchronization

On instantaneous voltage V ₂, inhibit signal V _iFour/one-period measure this moment again

On instantaneous voltage V ₃And synchronization On instantaneous voltage V ₄, then

{\dot{V}}_{Z} = V_{1} + j V_{3}, {\dot{V}}_{R} = V_{2} + j V_{4}

。For example, measure earlier for the signal voltage of 1KHz With

At the instantaneous voltage of synchronization, postpone 250 μ S then and measure again With Instantaneous value.

Secondly, calculate Z as follows _XValue, separate plural system of equations: Obtain: Z _X=R (V ₁+ jV ₃)/(V ₂+ jV ₄) order:

R_{X} = R (V_{1} . V_{2} + V_{3} . V_{4}) / (V_{2}^{2} + V_{4}^{2})

X = R (V_{2} . V_{3} - V_{1} . V_{4}) / (V_{2}^{2} + V_{4}^{2})

Then: Z _X=R _X+ jX

R _XExpression Z _XActive component, X represents Z _XReaction component,

Three, determine the value of measured element as follows:

Its value is R=R when element being measured is resistance;

Its value is C=1/ ω x when element being measured is electric capacity, and wherein ω is signal voltage V _iAngular frequency;

Its value is L=x/ ω when element being measured is inductance, and wherein ω is signal voltage V _iAngular frequency.

In measurement mechanism of the present invention, aforementioned calculation and judgment task are finished by single-chip microcomputer.Single-chip microcomputer is obtained R according to the above-mentioned relation formula _XAfter X, the measurement function that the measurement requirement that is provided with according to the symbol of X and operator is promptly selected, difference is found out corresponding relational expression, calculates the measurement result that needs and send display to show.

In order to measure respectively With , need a switch and switch.Use integrated analog switch 3, under Single-chip Controlling, finish to measure and switch.Operable integrated circuit has CD4051, CD4052, CD4066 etc.Analog switch makes the input end of differential amplifier 4 constantly be connected with the two ends of detected element and reference resistance respectively in difference, with the input of the signal voltage on it differential amplifier 4.This amplifier is a subtracting amplifier, finishes the pressure reduction computing on detected element and the reference resistance.It is made up of three operational amplifiers, referring to Fig. 8.IC2, IC3, IC4 and resistance R ₁-R ₉Form differential amplifier 4.Programmable amplifier 5 is sent in its output.In order to make accurately measurement signal value of single-chip microcomputer, should select enlargement factor according to the size of signal amplitude.Programmable amplifier can change enlargement factor to satisfy measurement requirement according to the size of signal under the control of single-chip microcomputer.

Single Chip Microcomputer (SCM) system is the control and the arithmetic element of measurement mechanism.Single-chip microcomputer in Single Chip Microcomputer (SCM) system (12) has selected 8098 for use, can certainly use other models.8098 have A/D converter, make circuit more succinct.Because test signal is bipolar signal, and 8098 can only handle unipolar signal, therefore needs a phase detector and a phase inverter.Phase detector 6 can detection signals positive and negative.Be output as timing when phase detector 6 detects programmable amplifier, 8098 directly carry out A/D conversion to this output signal, are output as when negative when phase detector 6 detects programmable amplifier, and this output signal is carried out the A/D conversion earlier again after phase inverter 7 is anti-phase.

When measuring the element of different numerical value,, need carry out the range conversion in order to improve measuring accuracy.Also weighing journey of benchmark precision resistance resistance among the present invention.In order to enlarge measurement range, to improve precision, a plurality of range resistance can be set.For example select resistance be 100 Ω, 1K Ω, 10K Ω, 100K Ω, 1M Ω one group of 5 switchable precision for metalfilmresistor more than ± 0.5% as range resistance, an analog switch is arranged, under the control of single-chip microcomputer, carry out the switching of benchmark precision resistance automatically, finish the automatic conversion of range.

Fig. 9 is one of embodiment of measurement mechanism of the present invention.Its hardware is made up of Single Chip Microcomputer (SCM) system and mimic channel two parts.

1,8098 Single Chip Microcomputer (SCM) system

8098 Single Chip Microcomputer (SCM) system are made up of 12 integrated circuit and some resistance, electric capacity, LED element, 5 charactrons and 6 function keys.U wherein ₄Being 8098, is the core of system.U ₅Adopt 8279 to be special-purpose interface devices, with U ₈(74LS138), U ₉(74LS245), U ₁₀(7407) finish control together to keyboard and display.U ₁(74LS138) and U ₂(74LS32) finish the address decoding of 8098 Single Chip Microcomputer (SCM) system.U ₆(74LS373) and U ₇(2764) the Add-In storer of composition system.U ₁₁(74LS273) be the 8D trigger, its effect is to start 6 luminotrons, shows measurement project and range.U ₁₂(74LS273) and U ₁₄(74LS07) finish to range in the simulation system change automatically, the selection of programmable amplifier enlargement factor and to V _Z, V _RMeasure the control of conversion.

2, mimic channel

Mimic channel is made up of 11 integrated circuit and some other elements.Signal source is formed sine-wave generator by a slice 8038 and peripheral cell, the signal voltage of exportable 100Hz, 1000H-Z and two kinds of frequencies.U ₁₅(LF347 four high guaily unit) finished the amplification and the equipotential of offset of sinusoidal signal and isolated the generation of current potential.U ₁₆, U ₁₇(CD4051) under the control of Single Chip Microcomputer (SCM) system, finish the automatic conversion of range.Analog switch U ₁₈(CD4052) finish signal voltage V on detected element and the reference resistance _Z, V _RMeasurement select.U ₁₉(LF356), U ₂₀(LF356) and U ₂₁(CD4052), U ₂₂(OP27) form the programme-controlled gain differential amplifier.U ₂₄(OP27) form phase inverter.U ₂₃(LM311) form phase detector.Also have high stable, a high-precision 5V reference voltage source that is made of LM336, the A/D converter power supply to 8098 guarantees conversion accuracy.

A kind of selectable model of above-mentioned each integrated circuit provides in the bracket of its code name back, also can select the homogeneous circuit of other models.Measurement mechanism of the present invention can be replaced by the higher chip of integrated level according to above-mentioned schematic diagram.For example above-mentioned Single Chip Microcomputer (SCM) system and artificial circuit part can be made on the chip piece, will dwindle the volume of measurement mechanism so greatly and lower its cost.

Measurement mechanism of the present invention has used single-chip microcomputer, and its software section mainly comprises master routine, initialization subroutine, test subroutine, Interrupt Process subroutine, data processing subroutine, nybble floating-point operation subroutine, digital display subroutine, self check subroutine etc.Main program block diagram is seen Figure 10.Initialization subroutine is finished interrupt mode setting, U ₅(8279) chip initiation, key in data processing and measuring-signal frequency are determined.Test subroutine is with the Interrupt Process subroutine, and it is right to finish

With The timing of real part, imaginary part voltage is measured, and measurement data is carried out digital filtering handle.The data processing subroutine then calculates R by operator's mode of operation and foregoing computing method _XWith the value of X, and further obtain the value of measured element.Digital display subroutine shows measurement result.The self check subroutine is finished the self check to 8098 systems and mimic channel, so that find the fault of measurement mechanism self rapidly.

The measuring process of measurement mechanism of the present invention is as follows.

The sinusoidal test signal of signal source output is added on detected element and the reference resistance, because the shielding action of equipotential buffer circuit equates the marking current that flows through detected element and reference resistance.8098 single-chip microcomputers are controlled two four analog switch U by the state that changes HS0.0 and HS0.1 end ₁₈Conducting state.When making HS0.0 and HS0.1 all be " 0 ", U ₁₈X end and X ₀Connect Y end and Y ₀Connect, the signal voltage at detected element two ends was delivered to 8098 A/D converter through amplifier and was carried out the A/D conversion this moment, measured Real part V ₁With imaginary part V ₃In distance

Behind the gating one-period, make that HS0.0 and HS0.1 are " 1 ", this moment U ₁₈X end and X ₃Connect Y end and Y ₃Connect, the signal voltage at reference resistance two ends send 8098 to carry out the A/D conversion and measure its real part V ₂With imaginary part V ₄It should be noted that above-mentioned two groups of numerical value are difference gating detected element and the synchronization of reference resistance in two signal periods, respectively the instantaneous value of measuring at a distance of 1/4th signal periods.To determine the positive and negative of input signal according to the state of phase detector carrying out A/D conversion preceding 8098, when signal is changed through the anti-phase A/D that carries out again earlier when negative.In addition, 8098 look the gain of the size control programmable amplifier of simulating signal, so that improve measuring accuracy.Because the frequency accuracy of signal source is bigger to the measurement result influence, and special frequency measurement link can be set, before each the measurement, the frequency of calibration signal source at first.Under 8098 control, the range conversion is finished automatically.To determine suitable range resistance according to the impedance of detected element on the one hand during the range conversion; To select the gain of programmable amplifier on the other hand according to the size of signal.

Claims

1, a kind of equipotential partition method is used for that online resistance, electric capacity, inductance element are carried out equipotential and isolates, it is characterized in that,

(1), the output terminal of an operational amplifier directly is connected with its inverting input, form a voltage follower;

(2), with an end of benchmark precision resistance (R) and segregate at kind of thread elements (Z _x) an end connect the other end of benchmark precision resistance (R) and signal source (V by lead _i) or the ground connection, segregate at kind of thread elements (Z _x) the other end by lead with ground or signal source (V _i) connect, benchmark precision resistance (R) is with segregate at kind of thread elements (Z _x) end that connects is connected with the in-phase input end of operational amplifier simultaneously;

(3), isolating points (C) all on the output terminal of operational amplifier and the wiring board is connected, definite method of isolating points (C) is: every in the circuit board and segregate at kind of thread elements (Z by lead _x) near signal source (V _i) the continuous resistance of an end (A), electric capacity, the other end of inductance element be isolation end (C).

2, a kind of the method for claim 1 of using is isolated in the method that line resistance, electric capacity, inductance element are measured, it is characterized in that,

(1), measured element is realized that equipotential isolates, its method is with the equipotential isolation method:

First, the output terminal of an operational amplifier directly is connected with its inverting input, forms a voltage follower;

Second, with an end and the measured element (Z of benchmark precision resistance (R) _x) an end connect the other end of benchmark precision resistance (R) and signal source (V by lead _i) or the ground connection, measured element (Z _x) the other end by lead with ground or signal source (V _i) connect benchmark precision resistance (R) and measured element (Z _x) end that connects is connected with the in-phase input end of operational amplifier simultaneously;

The third, by lead isolating points (C) all on the output terminal of operational amplifier and the wiring board is connected, definite method of isolating points (C) is: every in the circuit board and measured element (Z _x) near signal source (V _i) the continuous resistance of an end (A), electric capacity, the other end of inductance element be isolation end (C);

(2), measure signal voltage on the benchmark precision resistance (R) respectively

Complex values and measured element (Z _x) on signal voltage Complex values, then according to formula

Z_{X} = R * ({\dot{V}}_{Z} / {\dot{V}}_{R})

Calculate the value of measured element.

3, measuring method according to claim 2 is characterized in that, adopts the signal voltage on the following method measuring basis precision resistance (R)

With measured element (Z _x) on signal voltage And the value of definite detected element,

(1), measures a certain moment

Instantaneous voltage (V ₁) and synchronization Instantaneous voltage (V ₂), inhibit signal (V _i) four/one-period measure this moment again Instantaneous voltage (V ₃) and synchronization

Instantaneous voltage (V ₄), then

{\dot{V}}_{Z} = V_{1} + j V_{3}

{\dot{V}}_{R} = V_{2} + j V_{4},

(2), calculate (Z as follows _X) value, separate plural system of equations: Obtain Z _X=R (V ₁+ jV ₃)/(V ₂+ jV ₄) order:

R_{X} = R (V_{1} . V_{2} + V_{3} . V_{4}) / (V_{2}^{2} + V_{4}^{2})

X = R (V_{2} . V_{3} - V_{1} . V_{4}) / (V_{2}^{2} + V_{4}^{2})

Then: Z _X=R _X+ jXR _XExpression Z _XActive component, X represents Z _XReaction component,

(3), determine the value of measured element as follows:

Its value is R=R when element being measured is resistance;

Its value is C=1/ ω x when element being measured is electric capacity, and wherein ω is signal voltage (V _i) angular frequency;

Its value is L=x/ ω when element being measured is inductance, and wherein ω is signal voltage (V _i) angular frequency.

4, a kind of device that uses measuring method as claimed in claim 2 to measure online resistance, electric capacity, inductance element, the Single Chip Microcomputer (SCM) system (12) that comprises that form by single-chip microcomputer (8), display (9) and keyboard (10), a control survey process and calculating, demonstration measurement result, it is characterized in that

(1), have an equipotential buffer circuit that online measured element is carried out equipotential to isolate, this circuit has an operational amplifier (2), its output terminal is connected with inverting input, the formation voltage follower has a signal voltage source V _i(11), benchmark precision resistance R is connected signal voltage source V _iAnd between the in-phase input end of operational amplifier (2), the slotted line (13) of being drawn by the in-phase input end of operational amplifier (2) connects an end of detected element when measuring, the slotted line (15) of being drawn by the ground of measurement mechanism connects the other end of detected element when measuring, the many shielding wires of being drawn by the output terminal of operational amplifier connect all isolating points through determining on the wiring board at detected element place when measuring

(2), an integrated analog switch (3) is arranged, under the control of Single Chip Microcomputer (SCM) system (12), finish the voltage on the measuring basis precision resistance R With the voltage on the detected element

The time contact switch,

(3), a differential amplifier (4) is arranged, finish the voltage on the benchmark precision resistance R

The perhaps voltage on the detected element

Computing and amplification,

(4), there is a programmable amplifier (5) that the output valve of differential amplifier (4) is amplified, its enlargement factor can be controlled by Single Chip Microcomputer (SCM) system, size according to input signal amplitude is selected suitable enlargement factor, its output signal is handled by Single Chip Microcomputer (SCM) system after the A/D conversion, obtains the value of detected element.

5, measurement mechanism according to claim 4, it is characterized in that, single-chip microcomputer in the said Single Chip Microcomputer (SCM) system (12) is 8098,8098 and programmable amplifier (5) between a phase detector (6) and a phase inverter (7) are arranged, when detecting programmable amplifier, phase detector (6) is output as timing, 8098 directly carry out A/D conversion to this output signal, are output as when negative when phase detector (6) detects programmable amplifier, and this output signal is carried out earlier the A/D conversion again after phase inverter (7) is anti-phase.

6, according to claim 4 or 5 described measurement mechanisms, it is characterized in that, said benchmark precision resistance is that one group of switchable precision is the metalfilmresistor more than ± 0.5%, an analog switch is arranged, under the control of single-chip microcomputer, carry out the switching of benchmark precision resistance automatically, finish the automatic conversion of range.