INTRODUCTIONMr. Vijay Balu Raskar

B.E. Electrical Autocad-2D+3D

Mumbai University

Electronic Instruments

and Measurements

ElectronicDerived = Greek word ‘Elektron’ & ‘Electron mechanism’

Electron mechanism= “Study of behavior of the electrons under different conditions of externally applied fields”.

InstrumentsA device that requires skill for proper use.

Measurements Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc.

Refer for EMI Kalsi –Tata Mc Grow Hill

BASICS OF ELECTRICITY According to

the fundamental law of electromagnetic force

Video TimePRACTICAL - 01

In electromechanical systems, energy is stored in magnetic and electric fields.

These instrument are appropriately called as universal instruments.

Sr No.

NAME OF EQUIPMENT

PURPOSE

1 Ammeter Measures current

2 Voltmeter Measures p.d. between 2 points in circuit

3 Wattmeter Measures the power

4 Multimeter Measures V,I,R,C etc

5 LCR Meter Measures L,C & R

6 Oscilloscope Displays waveform of a signal

7 Ohm-meter Measures R

8 Signal Generator Generates signal for testing purpose

9 Network Analyzer Measures Network parameter

10 Q-meter Measures Q-factor of the RF circuits (Ratio of reactance to resistance)

11 Etc…………………………………….. ………………

AMMETER An ammeter is a measuring instrument used to measure the electric current in a circuit. UNIT= Amperes (A)Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters.

WORKING PRINCIPLE OF AMMETER

An ammeter consists of a coil with very low resistance. when electric current flows

through the coil, the coil induces a magnetic field which turns the needle.

As the currentthrough the coil increases, the plunger is drawn further into the coil and the pointer deflects to the right.

Wire carrying current to be measured.Spring providing restoring force

Basic Function of Moving AmmetersWith both moving coil and moving iron ammeters, an electric current is used to create magnetic energy, which in turn causes a moving part within the ammeter to shift in response. The amount of the shift moves a needle on the display, which in turn measures the amount of the current.

USE IT ?????

HOW TO USE AMMETER?HOW TO USE VOLTMETER?HOW TO USE WATTMETER?

HOW TO USE MULTIMETER?Calculation of R, L, C etc..HOW TO USE LCR METER?

HOW TO USE OSCILLOSCOPE?

TYPES OF AMMETER

Moving Coil AmmetersIn a moving coil ammeter, the magnet stimulates a coil that has the opposite polarity, causing it to be repelled from the magnet.

Moving coil ammeters have a linear display.

Moving Iron AmmetersIn a moving iron ammeter, two pieces of iron are housed inside of a coil that becomes magnetized and repels the two pieces of iron from one another. The result is a nonlinear, arced measurement.

Digital Display AmmetersA digital display has no moving parts, and instead measures the proportional drop across a reader located inside of the ammeter. Digital ammeters are far more accurate than their moving counterparts.

Indicating:- Indicates magnitude of quantity being measured. E.g.- Ordinary voltmeter, ammeter, wattmeter etc

Recording:- Recording over a specified period. E.g.- Recording voltages in a sub-station during the day.

Integrating:- Totalize events over a specified period of time. E.g.-Ampere Hour Meter (Energy).

There are two types of moving coil instruments.1. permanent magnet moving coil type which can only be used for direct current, voltage measurements.

2.The dynamometer typewhich can be used on either direct or alternating current, voltage measurements.

Permanent Magnet Moving Coil (PMMC)

The permanent magnet moving coil instruments are most accurate type for direct current measurements. The action of these instruments is based on the motoring principle. When a current carrying coil is placed in the magnetic field produced by permanent magnet, the coil experiences a force and moves. As the coil is moving and the magnet is permanent, the instrument is called permanent magnet moving coil instrument. This basic principle is called D’Arsonval principle. The amount of force experienced by the coil is proportional to the current passing through the coil.

In PMMC meter or (D’Arsonval) meter or galvanometer all are the same instrument.

Mathematical Representation of PMMC Mechanism:-

F = N B I L ⋅ ⋅ ⋅where ,

N: turns of wire on the coil I: current in the movable coilB: flux density in the air gap L: vertical length of the coil

DYNAMOMETER This instrument is suitable for the measurement of direct and alternating current, voltage and power. The deflecting torque in dynamometer is relies by the interaction of magnetic field produced by a pair of fixed air cored coils and a third air cored coil capable of angular movement and suspended within the fixed coil.

For small current measurement (5mA to 100mA), fixed and moving coils are connected in series.

While larger current measurement (up to 20A) , the moving coil is shunted by a small resistance.

VOLTMETERA voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit.

Working Principle of VoltmeterThe moving coil galvanometer is a type of voltmeter working on this principle.The voltmeter measures voltage by passing current through a resistance.It is designed in such a way so as to offer minimum disturbance to the circuit. This is made possible by using a sensitive ammeter in series with a high resistance.

Technically specified, all types of voltmeters are Ammeters because they measure current rather than the voltage. A voltmeter measures voltage only when current is transmitted in a circuit through a resistance. Due to this reason, voltmeters are sometimes referred to as high resistance Ammeters too.

Uses of Voltmeters

Voltage SensingVoltage Measurement

Electrical TestingEducational Laboratory

Electronics Industry

Types of Voltmeters1.Digital Voltmeters2.Analog Voltmeters3.Electrostatic Voltmeters (measure voltages without any charge transfer)

4.Oscilloscope Voltmeter(react fast enough to follow rapid voltage changes)

5. Microvoltmeters6. Electronic voltage meter or vacuum tube voltmeter (VTVM)

OscilloscopeAllows the amplitude of electricalsignals, whether they are voltage, current; power, etc., to be displayed primarily as a function of time.Depends on the movement of an electron beam.Beam to impinge on a phosphor surface

TransducersNon-electrical quantity isconverted into an electrical signal by a device called electrical transducer.

Non-electrical = electrical, mechanical, chemical, optical (radiant), or thermal.

Types of Transducers

1. Primary & Secondary2.Active & Passive3.Analog & Digital

Primary TransducerConverts energy from one form to electrical form (photovoltaic cell)

Secondary transducerCoverts any form to non electrical or signal form.(displacement transducer)

Active (self generating) transducers:-without any source of electrical excitation.(thermocouples, tacho generator)

passive transducers: in connection

with electrical power source.(a potentiometer, thermistor)

Analog transducer converts input signal into output signal, which is a continuous function oftime.

Digital transducer converts input signal into output signal in a discrete forms.

Displacement Transducerconvert the applied force into a displacement. Measured by following Electrical Principle:1) Capacitive 2) Inductive 3) Differential transformer 4) Photoelectrical 5) Potentiometer6) Ionization 7) Oscillation 8) Piezoelectric 9) Velocity

LVDT(Linear Variable Differential Transformer)

It is produces an electrical signal that is linearly proportional to

mechanical displacement.

emf opposes each other.Left when more flux links and so on

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