Ammeter
Ammeter is an electrical measuring device, which is
used to measure electric current through the circuit.
CONNECTION OF AMMETER IN CIRCUIT
An ammeter is always connected in series to a
circuit.
SYMBOL
Ammeter
Ammeter is a low resistance galvanometer
It is used to measure the current in a circuit in amperes
Galvanometer can be converted into an ammeter by
using a low resistance wire in parallel with the
galvanometer
 the resistance of the wire depends upon the range of
the ammeter
As shunt resistance is small the combined resistance of
the galvanometer & the shunt is very low hence the
ammeter has much lower resistance than galvanometer
An ideal ammeter has zero resistance
Voltmeter
Voltmeter is an electrical measuring device, which is
used to measure potential difference between two
points in a circuit.
CONNECTION OF VOLTMETER IN CIRCUIT
Voltmeter is always connected in parallel to a circuit.
SYMBOL
Voltmeter
Volt meter is a high resistance galvanometer
It is used to measure the potential difference between
two points of a circuit in volts
A galvanometer can be converted into a volt meter by
using a high resistance in series with the galvanometer
The value of resistance depends upon the range of the
volt meter
For voltmeter a high resistance, R is connected in series
with the galvanometer therefore resistance of voltmeter
is very large as compared to that of galvanometer
The resistance of an ideal voltmeter is infinity
Ohmmeter
The purpose of an ohmmeter, is to measure the
resistance placed between its leads.
This resistance reading is indicated through a
mechanical meter movement which operates on electric
current.
The ohmmeter must then have an internal source of
voltage to create the necessary current to operate the
movement
Also have appropriate ranging resistors to allow just the
right amount of current through the movement at any
given resistance
Simple ohmmeter circuit
Multimeter
A multimeter is a device used to measure electrical
current, voltage, and resistance.
A multimeter combines several electrical meters into
one handheld unit.
Basic multimeter models can measure voltage,
current and resistance.
Advanced models can also measure temperature,
inductance, capacitance, duty cycle and frequency.
They can also test diodes and transistors.
Some even work as an oscilloscope.
The two main types of multimeter are digital and
analogue
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