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

Color Value Color Value

Black

Brown

Red

Orange

Yellow

0

1

2

3

4

Green

Blue

Violet

Gray

White

5

6

7

8

9

Band 1 (closest to the end) – first digitBand 2 – second digitBand 3 – power of ten multiplier (most cases simply the number of zeros)Band 4 – tolerance (Red = 2%, Gold = 5%, Silver = 10%, none = 20%)

Resistor Color Band Code

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

• Brown Green Red Silver• Yellow Violet Orange Gold• Red Red Red

6

Determine the nominal value of resistance and the tolerance for resistors having the following color codes.

Determine the color code to specify each of the following resistors

• 1 kΩ• 390 kΩ• 56Ω