It includes it's symbolic representations, history, types and it's working, applications of Voltmeter. Can be used for presentations and as a reference too.

1. • Gowtham CR
• PES1201801581
• 4 - ‘A’
Presented
By -
• Prasanna Kumar
C
• Professor
• Dept. of EEE
Submitted
To -

2. It works on the principle that the torque is generated by the
current which induces because of measured voltage and this
torque deflects the pointer of the instrument. The deflection of
the pointer is directly proportional to the potential difference
between the points. The voltmeter is always connected in
parallel with the circuit.
Definition:
The instrument which
measures the voltage or potential
difference in volts is known as the
voltmeter.

3. The voltmeter is represented by the alphabet V inside
the circle along with the two terminals.

4.  The original principals behind voltmeters were
established by a Danish physicist named Hans
Christian Oersted (1777-1851) in 1820.
 When he discovered that an electric current in a wire
produced a magnetic field around it.
 The first ammeter, which is actually just an extremely
sensitive and non-resistive voltmeter, was used by
physicist Andre Ampere as early as 1820 to measure
current.

5.  But almost all types of voltmeters are founded off of
the models in which the pointers were attached to
moving coils, which were developed by French
physicist Jacques-Arsene d'Arsonval(1851-1940) in
1882.
 Since then, their measuring capacity has increased,
and some modern day models can measure up to
20,000 volts.

6.  Measurements of voltage are applicable in many
situations, but perhaps the most prevalent is it's part
in Ohm's Law, which states:
V=I*R when V=voltage[V], I=current[A],
and R=resistance[Ohms]
 Using this relationship, voltage readings can be used
along with another variable to determine another
unknown, or by knowing the value of current and
resistance we can calculate the voltage(or potential
difference) without the use of a voltmeter.

7.  The voltmeter constructs in such a manner that their
internal resistance always remains high. If it connects in
series with the circuit, it minimizes the current which
flows because of the measured voltage. Thus, disturb the
reading of the voltmeter.

8.  The voltmeter always connects in parallel with
the circuit so that the same voltage drop occurs
across it.
 The high resistance of the voltmeter combines with
the impedance of the element across which it is
connected.
 The overall impedance of the system is equal to the
impedance that the element had. Thus, no
obstruction occurs in the circuit because of the
voltmeter, and the meter gives the correct reading.

9.  The voltmeter is constructed with very high internal
resistance because it measures the potential difference
between the two points of the circuit. The voltmeter
does not change the current of the measuring device.
 If the voltmeter has low resistance, the current passes
through it, and the voltmeter gives the incorrect
result. The high resistance of the voltmeter does not
allow the current to pass through it and thus the
correct reading is obtained.

10. The voltmeter is classified into three ways. The classification of
the voltmeter is shown in the figure below.
Voltmeter
Classification On The Basis Of Output
Analogue Voltmeter
Digital Voltmeter
Classification On The Basis Of
Construction
Rectifier Type Voltmeter
MI Voltmeter
Electro Dynamo Voltmeter
PMMC Instrument
Induction Type Voltmeter
Classification On The Basis Of
Measurement
DC Voltmeter
AC Voltmeter

11. The following are the classification of instruments
regarding the displays of output reading.
 Analogue Voltmeter
 Digital Voltmeter

12.  The analogue voltmeter used for measuring the AC
voltage. It displays the reading through the pointer
which is fixed on the calibrated scale. The deflection
of the pointer depends on the torque acting on it.
The magnitude of the developed torque is directly
proportional to the measuring voltage.

13. The voltmeter which displays the reading in the
numeric form is known as the digital voltmeter. The
digital voltmeter gives the accurate result.

14. On the basis of the construction, the voltmeter is of the
following types.
 Rectifier Voltmeter
 MI Voltmeter
 Electro-dynamometer Voltmeter
 PMMC Voltmeter
 Induction type Voltmeter

15.  Such type of instrument is used in AC circuits for
voltage measurement. The rectifier instrument
converts the AC quantity into the DC quantity by
the help of the rectifier. And then the DC signal is
measured by the PMMC instrument.

16. Following are the two types of rectifier based AC
voltmeters.
1. AC voltmeter using Half Wave Rectifier
2. AC voltmeter using Full Wave Rectifier
1. 2.

17. The MI instrument means moving iron
instrument. This instrument is used for the
measurement of both AC and DC voltage. In this type
of instrument, the deflection is directly proportional to
the voltage of the coil.

18. The moving iron instrument is classified into two types.
1. Attraction Type Moving Iron Instrument
2. Repulsion Type Moving Iron Instrument
1. 2.

19. The electro-dynamometer voltmeter is used for
measuring the voltage of both AC and DC circuit. In
this type of instruments, the calibration is same both
for the AC and DC measurement.

20.  The PMMC works on the
electromagnetic effect.
 The PMMC voltmeter uses for
DC measurement. The accuracy
of the instrument is very high and
having low power consumption.
 The only disadvantage of the
instrument is that it is very costly.
 The range of the PMMC
voltmeter increases by connecting
the resistance in series with it.

21. • Induction type voltmeter uses a single winding to produce
flux .The flux produced by this winding is split up into two
fluxes , having phase difference with respect to each other.
• This is done by making a narrow slot in the poles of the
electromagnet.
• It essentially have an
electromagnet to produce
the required magnetic
field.

22. On the basis of the measurement, the voltmeter is of
the following types.
 AC Voltmeter
 DC Voltmeter

23. The instrument, which is used to measure
the AC voltage across any two points of electric circuit
is called AC voltmeter. If the AC voltmeter consists of
rectifier, then it is said to be rectifier based AC
voltmeter.

24. DC voltmeter is a measuring instrument, which is used
to measure the DC voltage across any two points of
electric circuit. If we place a resistor in series with the
Permanent Magnet Moving Coil (PMMC)
galvanometer, then the entire combination together acts
as DC voltmeter.

25.  These types of instruments
can handle both AC/ DC
voltages and resistance
measurements. These devices
use electronic amplifier in
between the input and the
meter.
 If this device uses the vacuum
tube in the amplifier then it is
called as Vacuum Tube
Voltmeter (VTVM). VTVM’s
are used in high power AC
measurements.

26.  Field Effect Transistor (FET) is a transistor that uses
electric field to control the electrical behavior of the
device.
 They are also known as unipolar transistors. Field
Effect Transistor based Voltmeter utilizes this
property of field effect transistors while measuring
voltage.

27. The applications of Voltmeter include:
 It is very useful in finding the voltage of a charge
storing device, such as to test the voltage of a battery.
For example, a new AAA cell will have about 1.6V, a
dying one perhaps 1.1V. A 12V lead-acid car battery will
read 12.5V when fully charged, or 14V when being
charged by the alternator in a car. If it reads 10V, there is
something wrong with the alternator.
 Verifying the power is on or off to the appliances.
 They are used to build a continuity tester, with a series
battery.

28.  It can be used just to tell whether there is power in a
circuit or not, such as a mains outlet.
 We can calculate the current by measuring the voltage
across a known resistance. This is useful when you
don’t have an ammeter.
 They are used to build an ohm meter, by using a voltage
divider with the unknown resistor.
 They are used to build an ammeter by measuring the
voltage across a shunt resistor.