Pengukuran Besaran ListrikRE 1323 Ohmmeter

RE 1323 Pengukuran Besaran Listrik1:Besaran-besaran listrik, tipe instrumen, metode langsung dan tidak langsung, Satuan dan standard, Kesalahan dalam pengukuran.2:Klasifikasi alat ukur, rectifier instrument 3:Penggunaan Amperemeter, Voltmeter dan Ohmmeter 4:Potensiometer5:Tahanan: rangkaian ekivalen, klasifikasi dan pengukuran tahanan rendah6:Pengukuran tahanan menengah dan tahanan tinggi 7:Pengukuran kapasitor8: 9 & 10:UTS

RE 1323 Pengukuran Besaran Listrik11: Pengukuran Induktor12: Instrumen Transformer (CT & PT) 13: Pengertian daya arus searah, daya arus bolak-balik 1 fasa & 3 fasa dan pengukuran daya arus searah14: Pengukuran daya arus bolak balik 1 fasa dan 3 fasa untuk beban setimbang dan tak setimbang15: Pengukuran daya reaktif dan contoh soal16: Penggunaan CRO (Cathode Ray Oscilloscope) dan contoh soal17 & 18:UAS

Ohmmeter tipe seriBila Rx = 0 (terminal A dan B dihubungsingkat), arus paling besar mengalir dlm rangkaian.Dlm keadaan ini, R2 diatur sampai jarum menunjukkan skala penuh. Posisi ini ditandai dg 0 . Begitu juga jika terminal A dan B terbuka, Rx =

Ohmmeter tipe shunt

Ohmmeter design (2)R1 and R2 are calculated from E and I full deflection.

Now that the right value for R has been calculated, we're still left with a problem of meter range. On the left side of the scale we have " and on the right side we have 0.

One might pause to wonder, "what does middle-of-scale represent? What figure lies exactly between zero and infinity?

If half-scale indication on any other type of meter represents 1/2 of the full-scale range value, then what is half of infinity on an ohmmeter scale?

The answer to this paradox is a logarithmic scale.

Ohmmeter design

Ohmmeter design

OhmmetersOhmmeters only function correctly when measuring resistance that is not being powered by a voltage or current source.

In other words, you cannot measure resistance with an ohmmeter on a "live" circuit! The reason for this is simple: the ohmmeter's accurate indication depends on the only source of voltage being its internal battery. The presence of any voltage across the component to be measured will interfere with the ohmmeter's operation. If the voltage is large enough, it may even damage the ohmmeter.

Pengukuran Besaran ListrikRE 1323 Potensiometer

PotensiometerInstrumen yg mengukur tegangan yg diketahui dg cara membandingkannya thd tegangan yg diketahui.Teg yg diketahui dpt disuplai dari sebuah sel standar atau sumber teg referensi yg diketahui.Pengukuran2 dg perbandingan menghasilkan akurasi yg lbh tinggikrn hsl yg diperoleh tdk tergantung defleksi jarum penunjuk;tp tergantung pd ketelitian teg standar yg diketahui tsb.

PotensiometerPotensiometer memanfaatkan kondisi setimbang atau kondisi nol.

Rangkaian dasar potensiometer:Potensiometer kawat geser (slide-wire)Tahanan total kawat geser: 200 ohm.

Awal: Kalibrasi / arus kerja distandarkan

Sel Standard 1.019 VoltPosisi kontak geser 101.9 cm (berarti 101.9 ohm)Tahanan geser diatur shg bila saklar ditutup, galvanometer tdk defleksi.->Arus kerja 10 mA

Rangkaian dasar potensiometer:Potensiometer kawat geser (slide-wire)Setelah dikalibrasi, setiap teg DC kecil yg tdk diketahui dpt diukur.

Kontak geser digerakkan sampai galvanometer tdk menunjukkan defleksi.

Shg teg sepanjang kawat geser sebanding dg posisi kontak geser (mis. 143 cm = 1.43 V)

Figure 23: Precision thermocouple slide-wire potentiometer Made by Leeds & Northrup, 1913.

Potensiometer Pengganti Tahanan geserTahanan Piring : 1 Switch 0.1 VoltKawat geser 200 skala1 skala = 0.0005 Volt

Potensiometer 2 Rangkuman

Penyederhanaan Potensiometer 2 RangkumanSekali instrumen dikalibrasi pada range x1, kalibrasi range x10 tdk diperlukan.->shg teg E hrs tetap sama pd kedua posisi range -> arus total batere hrs sama utk kedua posisi range.R(x1) = R(x0.1)

Rangkaian (a) Saklar x1 (b) saklar x0.1R(x1) = R(x0.1)Selanjutnya R2 ditentukan dg perhitungan

Potensiometer 3 Rangkuman

At the heart of the potentiometer is a long slide wire.

In the Type K potentiometer this was in the form of a ten-turn coil, a design due to Kohlrausch.

The potentiometer was used with an external standard cell and an external galvanometer.

POTENSIOMETER SEBAGAI KOTAK VOLTPotensiometer yang digunakan untuk pengukuran tegangan biasanya hanya pada 0 1.6 Volt. Jika tegangan yang diukur lebih besar digunakan rangkaian pembagi tegangan/kotak VoltBatas kesalahan sebuah kotak volt adalah 0.02%

From the 1940 Central Scientific Company catalogue:

Volt Box, L&N, for use with Students Potentiometer and Type K Potentiometer.

The volt box has three ranges which permit measurement and calibration up to 15, 150 and 300 volts, respectively.

Accuracy 0.04%.

The volt box on the left was made by James W. Queen of Philadelphia. It looks as if it has undergone some internal modifications. The paper labels notes that it will divide the input voltage by 200, 100 or 10.

POTENSIOMETER SEBAGAI KOTAK SHUNTKotak shunt dimaksudkan utk digunakan bersama potensiometer dalam pengukuran presisi arus searah dan untuk kalibrasi Amperemeter DC dan Wattmeter

Figure 15: Multirange Shunt Box Made by Leeds & Northrup Co., Philadelphia The multirange shunt allows the determination of currents from 0 A to 7.5 A,

Potensiometer untuk kalibrasi voltmeter dan ampermeterMetoda potensiometer umum digunakan untuk kalibrasi voltmeter, ampermeter, dan wattmeter.

Potensiometer Untuk Kalibrasi Voltmeter

Pembacan Skala Voltmeter DCPembacaan PotensiometerKoreksi0.00.000.01.00.95-0.052.02.00+0.053.03.05+0.15.04.1+0.1

Pembacan Skala Voltmeter DCPembacaan PotensiometerKoreksi6.06.15+0.157.07.10+0.18.08.15+0.159.09.20+0.2010.010.25+0.25

Potensiometer untuk kalibrasi voltmeter dan ampermeterBila sebuah voltmeter menerima kalibrasi awalnya, voltmeter tsb akan dilengkapi suatu skala baru:Teg yg tertera pd voltmeter diatur sampai potensiometer menunjukkan nilai yg diinginkan, lalu skala yg baru dituliskan.

Potensiometer Untuk Kalibrasi Amperemeter

Self Balancing Potensiometer

Potentiometer as electronic componentA potentiometer is a potential divider, a three terminal resistor where the position of the sliding connection is user adjustable via a knob or slider.

Tugas: Pelajari bab Tahanan untuk kuis pada pertemuan berikutnya.

Leeds and Northrup made a series of lesser potentiometers designed for introductory work by students. This student potentiometer has a single-turn slide wire instead of the ten-turn slide wire used in the Type-K series. This particular instrument is in the Greenslade Collection.

http://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Potentiometer/Potentiometer.html

Ohmmeter

Rp = tahanan pengatur nol ohm Rs = tahanan serieRi = tahanan dalam meterL = induktansi kumparan Rx = tahanan yang diukurE = sumber tegangan DC (baterai)IoRi

Io = mengukur 0 hmPada saat S = OpenIoIsRiRprRsIsERprRpr

IIsRiRpr+

RiI = 0.5IoRs+Ri

RiIo

Ohm Meter Shunt

What value of resistance between the test leads will cause exactly 1/2 scale deflection of the needle? For example, if we know that the movement has a full-scale rating of 1 mA (I full deflection), then 0.5 mA (500 A) must be the value needed for half-scale deflection.

http://gsc.nrcan.gc.ca/geomag/lab/virtual_museum/potentiometer_e.php

http://www.allaboutcircuits.com/vol_1/chpt_8/6.htmlhttp://physics.kenyon.edu/EarlyApparatus/Titlepage/Electrical_Measurements.htmlhttp://chem.ch.huji.ac.il/instruments/test/resistances.htm