DEFINATION DESIGN WORKING PRINCIPLE BLOCK DIAGRAM METHOD OF MEASUREMENT

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