Bilgisayar destekli karakteristik veren vektör empedansmetre tasarımı
The Computer aided characteristic providing vector impedancemeter design
- Tez No: 14177
- Danışmanlar: PROF.DR. ENİSE ERİMEZ
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1990
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 47
Özet
ÖZET Bu tezde özgün bir yaklaşımla empedans modülü - frekans, empedans faz açısı-frekans ve aynca empedans saf kapasitif ve saf endüktif olması durumunda ka yıp faktörü-frekans karakteristiklerini veren“ bilgisayar destekli karakteristik ve ren vektör empedansmetre”tasarımı gerçekleştirilmiştir. Bölüm birde, çeşitli empedans ölçme yöntemleri anlatılmıştır. Bölüm ikide, gerçeklenen karakteristik veren empedansmetreyi oluşturan devreler ile çalışma koşulları ve yazdım kısmına ait akış diagramı ayrıntılı bir biçim de şekil ve tablolarla açıklanmıştır. Bölüm üçte devrelerde kullanılan elemanların değerlerinin hesaplan, ölçüle cek empedansın ölçüm aralığı, ve bu aralıklarda yapılan ölçüm hatalarına ilişkin he saplar ve tablolarla verilmiştir. Ek bölümünde karakteristik veren empedansmetreyi denetleyen ve sonuçla rı sağlayan yazılım kısmına ait Turbo C programları verilmiştir.
Özet (Çeviri)
THE COMPUTER AIDED CHARACTERISTIC PROVIDING VECTOR IMPEDANCEMETER DESIGN SUMMARY There are many methods for designing impedance measurement bridges, such as Schering bridge, Maxwell bridge, etc. However these methods suffer from the difficulty of obtaining the balanced condition and also these methods are usually used for measuring capacitive or inductive impedances Also there are many electronic met hods for impedance measurement such as the vector impedance methods. But this measurement depends on having a constant current passing thorugh the un known impedance which is difficult to obtain for capacitive and high value impedan ces. There is another electronic method for measuring a impedance such as two sinu soidal waves but this method is sensitive to the change in amplitude of the two input waves. In this thesis characteristic values providing vector impedancemeter is reali zed. This impedancemeter gives the impedance modul-frequency, the impedance phase angle-frequency and in case of pure capacitive or inductive impedance, the loss factor-frequency characteristics. In chapter one, previous methods are investigated. Chapter two introduces the operation of characteristic values providing im pedancemeter with its detailed properties. Operation of circuits and schames of circu its are also given. Flow chart for programming of (IP is also given In chapter three, measurement errors, the measurement range of impedance value and autorange components values are given and calculated. In the appendix chapter, measurement programming in C and assembly lan- guages,and print -outs of measurement charateristics are also given THE BASIC THEORY FOR IMPEDANCE MEASUREMENT Fig 1. Shows the basic circuit used for impedance measurement. The unknown impedance is connected in series with the known resistance R to an oscilla tor whose frequency is f. Since Iz = IR¦Vı © v: R Fig 1 The Basic circuit for measuring a impedance (1) (2) Basic circuit for measuring impedance If Vj and V^ sinusoidal voltages are transformed to square waves and produced a rectangular waveform time-interval between to this square waves by using EX-OR gate and if this time interval is mesau- red, the phase angle of the impedance is easily calculated. Let the oscillator voltage V constant with frequency f. If current through the unknown impedance is measured then the ratio of the oscillator voltage to the cur rent through the unknown impedance gives the impedance modul. By using this basic idea for impedance measurement one can easily obtain the impedance value. The Block Diagram Of The Characteristic Providing Vector Impedancemeter In order to design the charatceristic providing vector impedancemeter, it is sufficient to measure the time-interval corresponding to the phase angle and to find the impedance modul by using oscillator with constant voltage and frequency, it is sufficient to measure the current through unknown impedance, then with evaluating these values one can obtain desired characteristic by using hardware and software techniques. The block diagram of characteristic values providing impedancemeter is shown Fig 2. IIOscillator whose frequencies controlled by uP ~~7H Z Unknown impedance ? B know resistances and theirs oto-range circuit current to voltage con verter otoran^ ge circuit £ Fu! wave recliferand evening filter Difference circuit Ml The impedan ce character determining. circuit ADC £==> Holder and counter circuit St up Fig 2 - Block Diagram of the chracteristic provding vector impedancemeter The operation of this impedancemeter is given below. The oscillator produces sine voltage whose maximum peak value is constant and, whose frequencies data are given by uP, gives the first frequency data to the oscillator. The fourth digitial switch belongs autorange device is switched on by UP. The current through the unknown im pedance yields a voltage on the known resistance R in the autorange device. Depen ding on this voltage, UP selects proper R resistance of the autorange circuit and saves this value of the R resistance. After this operation, the first and second digital cont rolled switches are swithced on by UP. Then operation of the difference circuit begins and the phase diffrence pulses are obtained. The holder circuit holds only one the pha se difference pulse and the counter counts the duration of the this one phase differen ce pulse by using the proper counter oscillator, the binary number obtained from co unter is saved in the stack of HP. The count operation of one phase difference pulse is made ten times because of reducing the random effects on the measurement errors. Transforming these binary numbers to decimal numbers, (iP can calculate the mean of these numbers which are corresponding to the phase difference time-interval, and saves it in the stack memory. At the same time, the impedance character determining circuit gives the data belong to whether the impedence is inductuve or capactive to uP. inAfter this operation finished. First and second digital controlled switches are switched off and third digital controlled switch is switched on for begining to measure the current thorugh the unknown impedance by |xP. The current thorugh the unknown impedance is transformed to the voltage for obtaining current data. Since this voltage is sinusoidal voltage and to measure the maximum peak value of this voltgae is diffucult esspecially in case of high frequen cies so it should be taken the average of this voltge, it must be used a full wave rectifi er and averaging filter. The constant d.c. value belongs to the current is obtained from fullwave rectifier and averaging filter is transformed to a digitial word by Analog/Di gital Converter. The obtained digitial word is named current data. The current data is determined as the current through the unknown impedance value. This value must be obtained ten times because of reducing the random effects on the measurement er rors. The mean of this value is taken account then by taking acccount osilaitor inter val resistance, auto-range resistance values and the number belongs to phase diffe rence, [iP calculates the impedance modul, the impedance phase angle,the impedan ce reactance. In this calculation |iP corrects all of method error. For the others determined frequencies' data,this operations are repeated and other data belongs to modul, pahase angle, real and imaginary parts of impedance are obtained and saved in stack. By using these data ^P draws the impedance modul fre quency,the impedance phase angle-frequency and in case of the pure inductive or ca- pactive impednance the loss-factor-frequency characteristics. The flow chart belongs to software part of this impedancemeter is given be low. IV3eein Set to data belongs to the frequencies of oscilator, the auto- range circuits resistances values, counter osilators frequencies and oscillator voltage and operation repeating numbers Sent the F = 1 st frequency data to oscillator Switch on the first autorange digitial control led switch and begin to autorange operation Sent to first value of the autorange 1 resistance R to autorange curcuit Switch off the au torange 1 curcuit and save the value ofR This impedance is out of mesau rement range 3 STOP 3TOP Give the bigge value of the R resistance rthe conî* ^arator out put of the aut range.101/' NRead the data belongs to impedance character Switch on the impedance modul measuring circuit M-I+l Begin to autorange 2 ope ration with smallest value of autorange 2 resistance R >the\ j^omparator> ^the output of aut range 2 cut/ ' »cuitO?/ N 1=1 st repeating operation Switch on the full wave rectifier and averaging filter Read the data obtained from ADC and set it In to the stack memorj N 4 VITransform the binary number belongs to the phase difference to decimal number and take mean of them, then save it in the memory Evaluate the data from ADC and take the mean of them, set it memory 360-fp.N fso 2Roto2 I R=(2-17). equation = Vzö 2 2RR0 - R2n ,ZR and the corresponding frequencies F+l Use the second counter oscil lator N VII
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