jlml

1. ELECTRICAL AND ELECTRONIC
MEASUREMENTS

2. SYLLABUS
OVERVIEW

3. UNIT-I MEASUREMENT
SYSTEM AND MEASURING
INSTRUMENTS
Generalized Measurement system,
Classification of instruments, Error in
measurement, Classification of errors.
Principle, Construction, Operation of
Moving Coil and Moving Iron Instruments -
Ammeters and Voltmeters - Single phase
Watt meters and Energy Meters - D.C &
A.C Potentiometers - Instrument
Transformers- Instruments for
Measurement of Frequency and Phase-
Calibration of watt meter.

4. UNIT-II MEASUREMENT OF
R,L,C USING BRIDGES
D.C Bridges: Wheatstone - Kelvin double
bridge- Megger – A.C Bridges: Anderson
Bridge –Maxwell Bridge- Hay’s Bridge
and Schering bridge - Measurement of
Unknown Capacitance using Schering
Bridge.

5. UNIT-III ELECTRONIC
INSTRUMENTS
Analog Meters: D.C Ammeter and Voltmeters
- Multimeter - Q meter - True RMS Meter -
Vector Impedance Meter - RF Voltage and
Power Measurements - Instrumentation
Amplifier.
Digital Meters: Digital Tachometer – DMM-
ADC: Successive Approximation, Dual
Slope –DAC: Weighted Resistor, R-2R
Ladder type- Digital Frequency Counters -
LCR meter- Calibration of DC Ammeter
and DC Voltmeter.

6. UNIT-IV DIGITAL STORAGE
OSCILLOSCOPE AND SIGNAL
GENERATORS
Analog Storage Oscilloscope - Sampling
Oscilloscopes - Digital Storage
Oscilloscopes - Sine Wave Generator -
Sweep Frequency Generator, Pulse and
Square Wave Generator - Wave
Analyzer: Harmonic Distortion Analyzer -
Spectrum Analyzer- Measurement of
frequency and voltage at different ac
inputs using DSO.

7. UNIT-V SMART
INSTRUMENTS AND
RECORDERS
Serial, Parallel ports, USB–IEEE 488-
Applications of Digital Instruments-
Elements of Data Acquisition - Smart
Sensor. Acquiring and Generating
Signals using DAQ Card.
Recording Devices: X-Y Plotters, Magnetic
Tape Recording - Data Loggers- Display
Devices: LED, LCD

8. MEASUREMENT
The measurement of a given quantity is
essentially an act or the result of
comparison between the quantity
(whose magnitude is unknown) and a
predefined standard.

10. Two Basic Requirements
 The standard used for comparison
purposes must be accurately defined
and should be commonly accepted.
 The apparatus used and the method
adopted must be provable.

11. METHODS OF
MEASUREMENTS
 Direct method
 Indirect method

12. Direct Method
 The unknown quantity (also called the
measurand) is directly compared against
a standard.
 Result is expressed as a numerical
number and a unit. The standard, in fact,
is a physical embodiment of a unit.
 Quite common for the measurement of
physical quantities like length, mass and
time.

13. Drawbacks of direct Method
 Not always possible, feasible and
practicable.
 Most of the cases, are inaccurate
because they involve human factors.
 Less sensitive.
 Hence direct methods are not preferred
and are rarely used.

14. MEASURING SYSTEM
(Indirect Method)
 A measurement system consists of a
transducing element which converts the
quantity to be measured in an
analogous form.
 The analogous signal is then processed
by some intermediate means and is then
fed to the end devices which present the
results of the measurement.

15. INSTRUMENT

16. INSTRUMENT
 An instrument may be defined as a device
for determining the value or magnitude of a
quantity or variable.
 The earliest scientific instruments used the
three essential elements as our modern
instruments do. These elements are
 (i) a detector,
 (ii) an intermediate transfer device, and
 (iii) an indicator, recorder or a storage
device.

18. MECHANICAL
INSTRUMENTS
 These instruments are very reliable for
static and stable conditions.
 But they suffer from a very major
disadvantage. They are unable to
respond rapidly to measurements of
dynamic and transient conditions.

20. ELECTRICAL
INSTRUMENTS
 Electrical methods of indicating the output
of detectors are more rapid than
mechanical methods.
 It is unfortunate that electrical system
normally depends upon a mechanical
meter movement as indicating device.
 This mechanical movement has some
inertia and therefore these instruments
have a limited time (and hence, frequency)
response.

22. ELECTRONIC
INSTRUMENTS
 These instruments require vacuum tubes or
semiconductor devices. Recent practice is to
use semiconductor devices as they have
many advantages over their vacuum tube
counterparts.
 Since in electronic devices, the only
movement involved is that of electrons, the
response time is extremely small on account
of very small inertia of electrons
 example, a C.R.O. is capable of following
dynamic and transient changes of the order of
a few ns (l0-9 s).

23. WORKING OF CRO

24. Absolute Instruments
 These instruments give the magnitude
of the quantity under measurements in
terms of physical constants of the
instrument.
 The examples of this class of
instruments are Tangent Galvanometer
and Rayleigh's current balance.

25. Secondary Instruments
 These instruments are so constructed
that the quantity being measured can
only be measured by observing the
output indicated by the instrument.
 These instruments are calibrated by
comparison with an absolute instrument
or another secondary instrument which
has already been calibrated against an
absolute instrument.
 Examples: Voltmeter, pressure gauge

26. Analog and Digital Instruments
Secondary instruments work in two modes :
(i) Analog mode, and (ii) Digital mode.
 Signals that vary in a continuous fashion and
take on an infinity of values in any given range
are called analog signals. The devices which
produce these signals are called analog
devices.
 In contrast, the signals which vary in discrete
steps and thus take up only finite different
values in a given range are called digital
signals. The devices that produce such
signals are called digital devices.

27. Indicating Instrument
 Instruments and systems use different kinds of
methods for supplying information concerning
the variable quantity under measurement.
 Most of the time this information is obtained as
a deflection of a pointer of a measuring
instrument. In this way the instrument
performs a function which is commonly known
as indicating function.
 For example, the deflection of pointer of a
speedometer indicates the speed of the
automobile at that moment. A pressure gauge
is used for indicating pressure'.

28. Recording Instruments
 In many cases the instrument makes a
written record, usually on paper, of the
value of the quantity under measurement
against time or against some other
variable. Thus the instrument performs a
recording function.
 For example, a potentiometric type of
recorder used for monitoring temperature
records the instantaneous temperatures on
a strip chart recorder.

29. Integrating Instrument
 The integrating instrument measures the
total energy supplied by the circuit in a
given interval of time. It is independent
of the rate at which the total energy
consumed.
 The watt hour meter is the example of
integrating instruments. This type of
meter directly measures the energy in
watt hour.