A multimeter is a laboratory instrument that can measure AC/DC voltages, currents, and resistance with a digital display. It has three main parts: a display, a selection knob to choose the measurement function, and ports to connect probes. To measure voltage, the probes are connected to the circuit and the knob is set to the voltage setting. To measure resistance, the knob is set to the resistance setting and the probes are connected across a resistor. Multimeters provide accurate digital readings and can measure several circuit parameters with one device.

1. BY : PRAPTI BORTHAKUR
POWIET

2. DEFINATION
DESIGN
WORKING PRINCIPLE
BLOCK DIAGRAM
METHOD OF MEASUREMENT

3. It is a common and important laboratory instrument .It contains three
different meters in one.
• It is use to measure AC or DC voltages
• It is used to measure AC/DC current and resistance with digital display.
• It gives digital output , which is very accurate. As the name suggest ,
multimeter are those measuring instruments which can be used to calculate
multiple circuit characteristics.

4. A multimeter has three parts:-
DISPLAY
SELECTION KNOB
PORTS

7. Two probes are plugged into two of the ports on the front of the
units.
COM stands for common and is almost always connected to the
ground of a circuit.
10A is the special port used when measuring greater currents (
greater than 200mA)
mAVΩ is the port that the red probe is conventionally plugged
into.This port allows te measurement of current (upto 200 mA),
voltage and resistance.

9. • The PCB contains an assortment of various components including
various types of resistors, capacitors, diodes and IC’s. Also it host the
battery, crystal oscillator, PTC , LCD and the buzzer which test the
continuity of device under test.

10. • The PCB is bound to the top casing og the multimeter with
the help of screws.A LCD and a rotary knob switch are
sandwiched between the top casing and the other side of
the PCB. Allso,the contacts for switching the multimeter ON
and OFF can be seen.
• Some multimeter employs the rotary switch to handle the
switching ON & OFF options while some requires a slider
switch.
• The selection knob allows the user to set the multimeter to
read different things such as milliamps(mA) of
current,voltage and resistance

11. • A LCD is embedded on the PCB and is interfaced through pinouts on
the PCB itself.
• A transparent plastic casing is over the LCD protecting it from the
scratches.Also shock absorption is provided by the rubber pads
closely attached at the top and bottom of the LCD.
• The display usually has four digits and the ability to display a negative
sign.A few multimeter have illuminated displays for better viewing in
low light situations.

13. • The V– (*) setting is for
measuring DC voltages.
Eg. battery voltage.
• The V~ (*) setting is for measuring
AC voltages.
Eg. house voltage
• The 20 (*) setting is to measure
DC voltages in the volts (V)
range.

14. MEASURING VOLTAGE
• Set the dial to the a
value greater than the
voltage being
measured.
• For our labs, we will
be working with the
20 V range.

15. FUNCTION SWITCH MEASURING RESISTANCE
& CURRENT
• The Ω setting (*)is used to
Measure electrical
resistance in Ohms.
The A setting
(*) is used to
measure DC
current in
amps.

16. MEASURING RESISTANCE
Set the dial to a value
greater than the
resistor value being
measured.
The 1 in the
display means the
resistance is higher
than the current
dial setting
For a 5000 ohm
resistor, set the dial to 20K.
For a 300 ohm
resistor, set the
dial to 2000

17. ADVANTAGES OF DIGITAL MULTIMETER
• Very high accuracy
• Has very high input impedance which ensures less loading effect on
the input
• The numeric display of digital meters provides zero parallax error.

18. DISADVANTAGES OF DIGITAL MULTIMETER
• It does not do well with measurement fluctuations
• It is more expensive than the analog type
• It can be difficult to find one for your specific needs