CN2128386Y

CN2128386Y - Digital impedance parameter measurer

Info

Publication number: CN2128386Y
Application number: CN 92227689
Authority: CN
Inventors: 李文辉
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-06
Filing date: 1992-07-06
Publication date: 1993-03-17
Anticipated expiration: 2002-07-06

Abstract

The utility model relates to a digital impedance parameter measurer capable of measuring the parameters of equivalent inductance, capacitance and resistance in series and in parallel. The measuring method is a 'vector method', and a reactance component and a resistance component can be separated, so that actual pure inductance, pure capacitance capacitor and pure resistance resistor (alternate current resistance resistor) can be measured. A measurement range can reach from 0.1 mu H to 200H, from 0.1pF to 20m omega, and from 0.1 omega to 100Mm omega, and a basic accuracy can reach +-0.5%rdg. The utility model is composed of the circuits of a half bridge, a constant current/constant voltage oscillator, a phase-sensitive detector, etc., and is applicable for industrial production, scientific research, education and electric apparatus maintenance departments.

Description

Digital impedance parameter measurer

The utility model relates to a kind of impedance parameter surveying instrument

The existing digital inductance capacitance table of a kind of DT-902 type, form by half-bridge, constant current, constant voltage oscillator, phase-sensitive detector (PSD) etc., have six electric capacity ranges (2nF, 20nF, 200nF, 2 μ F, 20 μ F, 200 μ F) and six inductance ranges (200 μ F, 2mH, 20mH, 200mH, 2H, 20H), adopt key switch to carry out range control.This table has adopted low power consumption integrated circuit TL062 directly as signal source output stage follower in order to reduce power consumption, because the big current work characteristic of TL062 is relatively poor, therefore when tested resistance value hour (promptly measure small inductor and greatly during electric capacity), working current is big, causes constant current/constant voltage oscillator defect out of control easily; Similarly, the electric current of its half-bridge---electric pressure converter also is directly to adopt amplifier to do, and working current is big when measuring the low value impedance, can cause waveform distortion, influences precision.The range of this table still not enough (directly measurement range is 0.1 μ H～20H, 1pF～200 μ F) in addition.

The utility model purpose is to provide a kind of range big, easy to use, low in energy consumption impedometer.

The utility model is achieved in that (with reference to the following drawings)

Fig. 1. be theory diagram of the present utility model.

Fig. 2. for expanding current circuit.

Fig. 3. be 1/ ∞ ²The parameter correction circuit.

Fig. 4. be double integration A/D, the electronic switching circuit of input, reference terminal.

Fig. 5. be the half-wave phase-sensitive detection circuit.

Z _xBe tested impedor, amplifier A₁、A ₂Form half-bridge circuit, S with the range resistance R₁、S ₂Be the function change-over switch, rectifier D, proportion resistor R₁、R ₂, comparator C OMP, oscillator OSC etc. consist of a constant voltage/constant current oscillator by half-bridge. Measure parameter in parallel (such as equivalent capacity C in parallel_p) time be constant voltage output, S at this moment_1aReceive " 1 ", measuring the series connection equivalent parameters then is constant current output, S₁Receive " 2 " end.

The two-way output of half-bridge is through S₁Switch one road U_yAs the phase-sensitive detector input signal, after 90 ° of another Lu Zejing phase shifts as the reference signal of examining mutually device. The output signal of rectifier needs by different functions from the output signal of phase-sensitive detector, by S₂Switch, be sent to respectively double integral A/D converter, utilize double integral A/D converter input signal V₁With reference signal V_rThe function of being divided by, finish division arithmetic, and convert numeral to and show. In fact this instrument utilizes the division function of phase-sensitive detector and double integration A/D, has finished vector and has been divided by, and has realized " vector method " measurement. Owing to when measuring series equivalent capacitance ∞ need to be arranged²Parameter correction. Therefore, be provided with amplifier A₃, its gain is ∞²／10 ⁿ, (wherein n is the parameter relevant with frequency, when frequency f=10³The time, n=3) S_2aSpecial in A₃Control. When measuring AC resistance, only need 90 ° of phase shifters are removed just passable.

1. when measuring equivalent capacity Cp in parallel, Ux meets A ₁, Uy meets A ₂, V _rMeet attenuator α, V _iConnect and examine device PD mutually, phase shifter is connected into+90 ° of phase shifts, and at this moment, the equiva lent impedance of half-bridge input end is:

Z _x＝1／（G _p＋j∞C _p）（1）

Wherein: G _pBe shunt conductance

C _pBe equivalent capacity in parallel

And have: U _x=I/(G _p+ j ∞ C _p) (2)

U _y＝－IR＝－U _x·R（G _p＋j∞C）（3）

V _r＝｜U _x｜·K _d·α （4）

Wherein: K _dBe efficiency of rectification

α is the attenuator coefficient, α=α ₀∞, α ₀Be constant

V _i＝｜U _y｜ _Im·K _p＝K _p·｜U _x｜·R·∞·C _p（5）

Wherein: K _pFor examining device efficient mutually

| U _y| _ImBe U _yImaginary part

Digital watch displayed value N is:

N＝（V _i／V _r）×10 ³＝（K _p·R·10 ³·C _p）／K _d·α ₀（6）

Order: K=(K _pR10 ³)/(K _dα ₀)=(constant) (7)

Then have: N=KC _p(8)

2. measure series connection equivalent inductance L _sThe time, U _xMeet A ₂, U _yMeet A ₁, the phase shifter phase shift is+90 °.

At this moment:

Z _x＝R _s＋j∞L _s

Can get through similar derivation:

N＝K′·L _s（9）

In the formula: K '---be similar to the coefficient of K

3. measure series equivalent capacitance C _sThe time, U _xMeet A ₂, U _yMeet A ₁, the phase shifter phase shift is+90 °, P _DMeet A ₃, V _rReceive α output, V _iReceive α output; At this moment:

Z _x＝R _s＋1／（j∞C _s）（10）

U _x＝－IR （11）

U _y＝－ (U _X)/(R) （R _s＋ 1/(∞Cs) ）（12）

V _i＝｜U _x｜·K _d·α

＝｜U _x｜·K _d·α ₀·∞ （13）

V _r＝｜U _y·（－∞ ²／10 ⁸）｜ _Im·K _p

＝K _p·｜U _x｜·∞／（R·C _s·10 ⁸）（14）

N＝KCs （15）

Wherein: ∞=2 π f=2 π * 10 ³

F is oscillator frequency 1Kz

The utility model has improved the output characteristics of oscillator owing to adopted expansion current circuit as shown in Figure 2, has also kept the little characteristics of quiescent dissipation simultaneously, can be by stacking powered battery.In addition, the series equivalent capacitance method of testing that the utility model adopts can directly be measured (need not pass through and convert) following all kinds of capacitors of 20mF.Because the utility model has adopted single 1KHz sine-wave excitation, the influence that frequency error causes can be by adjusting circuit parameter (α ₀) and offset fully, thereby reduced global error.The utility model can be used for electronics, power industry and research and teaching, electrical maintenance all departments, measure various inductors, capacitor, its range ability can reach: 0.1pF～20mF, 0.1 μ H～200H, 0.1 Ω～200M Ω, basic accuracy is ± 0.5%rdg that quiescent dissipation is 4.5mA/9V, than generally much superior with quasi-instrument.

Claims

1, a kind of digital impedometer can be measured the series connection equivalent inductance; The series and parallel equivalent capacity, parameters such as resistance have adopted double integral A/D converter, it is characterized in that: include half-bridge, constant current/constant voltage oscillator, phase-sensitive detector (PSD), function switch, ω ²Correcting circuit.

2, instrument according to claim 1, it is characterized in that: the electric current of constant current/constant voltage oscillator and half-bridge---electric pressure converter is added with the expansion current circuit of being made up of NPN and PNP transistor.

3, instrument according to claim 1 is characterized in that: ∞ ²Correcting circuit is made of amplifier, and it only is used for series equivalent capacitance and measures.

4, instrument according to claim 1, it is characterized in that: function switch is made of two groups of buttons, and wherein one group is used to control the conversion of series and parallel measurement pattern, and another group is used for control-∞ ²The input of correcting circuit and double integration A/D converter, reference edge.