Digital Multimeter (DMM)
Used to measure the following:
Voltage – DC and AC
Current – DC and AC
Resistance
Capacitance
Temperature – w/ extra probe
Also used to check:
Diodes
Transistors
1
We’ll Use the DMM to Measure
Resistance
• Resistors restrict the flow of current, given a
fixed voltage
• Unit = Ohms, Ω
• They come in different packages
2
Color Code
• The resistors we’ll test have a color code
to identify their resistance and tolerance.
3
Resistor Color Band Code
Band 1 (closest to the end) – first
digit
Band 2 – second digit
Band 3 – power of ten multiplier
(most cases simply the number of
zeros)
Band 4 – tolerance (Red = 2%, Gold
= 5%, Silver = 10%, none = 20%)
Color
Value
Color
Value
Black
Brown
Red
Orange
Yellow
0
1
2
3
4
Green
Blue
Violet
Gray
White
5
6
7
8
9
4
What is “Tolerance” about?
• If a resistor has a nominal value of 1000 Ω
and a tolerance of ± 10 % then individual
resistors with the same nominal value are
allowed to vary in their actual values from
900 Ω to 1100 Ω and still be considered
acceptable.
• Any resistor fabricated with an actual
value outside that range should be
rejected as “not meeting specifications”.
5
Practice Problems
Determine the nominal value of resistance and
the tolerance for resistors having the following
color codes.
• Brown Green Red Silver
• Yellow Violet Orange Gold
• Red Red Red
Determine the color code to specify each of the
following resistors
• 1 kΩ
• 390 kΩ
• 56Ω
6