Download 08-Ohmmeter

Done by:
Khalid Hijjawi
Mohammad Massad

Is an electrical instrument that
measures electrical resistance, the
opposition to an electric
current. The unit of measurement
for resistance is ohms (Ω).
 The
main principle that
ohmmeter works with is:
R=V/I
(Ohm’s Law)
Types of ohmmeters
1.Analog ohmmeters
2.Digital ohmmeters
Analog Ohmmeters
1.Series type ohmmeter:
R1:the currernt limiting
resistor
R2: Zero adjust resistor
Rx: Unknown resistor
E: internal battery
Rm: internal resistance of
the d’Arsonval
movement
2.Shunt type ohmmeter:
same as series type but
used for low resistance
measurements because of
its high accuracy
 1.
Measuring the
resistance when the circuit
element is connected as part
of a larger circuit

2. You cannot
measure the
"resistance" of a
non-linear
element
although ohmme
ters can be used
to identify the P
and N sides of a
diode

3. Measuring
while your
hands touching
the leads of the
circuit element
Mega
ohmmeter

is a special type
of ohmmeter used to
measure the electrical
resistance of insulators.
Insulating components,
for example cable
jackets, must be tested
for their insulation due
to their usage in high
voltage electrical
equipment and
installations.

For this purpose
megohmmeters, which
can provide high DC
voltages (typically in
ranges from 500 V to
2 kV) at specified
current capacity, are
used. Acceptable
insulator resistance
values are typically 1 to
10 megohms,
depending on the
standards referenced.
1.Electronic Type (Battery operated)
2.Manual Type (Hand operated)

is a piece
of electronic test
equipment used to
measure capacitance
, mainly of
discrete capacitors.
* The signal at the output of N2 is
invariably a square wave.
The square waves are basically
just continuous and alternate
generation of the positive voltage
and zero voltage.
* The capacitor CX which is to be
measured is connected to the
output of the buffers as shown in
the figure.
* During a positive peak of
the square wave, the unknown
capacitor CX charges up to the
supply voltage and at the next
zero voltage pulse it discharges
almost instantly through D1.
LCR meter
An LCR meter (Inductance
(l), Capacitance (C), and
Resistance (R)) is an
instrument used to
measure the inductance,
capacitance, and resistance
of a component, sensor or
other device that’s
operation depends upon
capacitance, inductance or
resistance.

Test frequency : An instrument with
a wide frequency range and multiple
programmable frequencies provides
this platform. Common
measurement frequencies are
50/60Hz, 120Hz, 1kHz, 100kHz and
1MHz
At the balance point the bridge
component positions can be
used to determine the value
of the component under test.
This method is typically
used for lower frequency
measurements - often
measurement frequencies of
up to 100 kHz or so are
used.
Diode measurement
-
-
One of the basic ohmmeter
application, is the
determination of cathode and
anaode .
Also determining the forward
active mode resistance.

The resistance of
forward active mode is
very low compared to
the resistance of
reversed mode. So based
on this the cathode and
anode is determined.

There may be some
errors in measuring
the forward
resistance.