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

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

Color Code The resistors we’ll test have a color code to identify their resistance and tolerance.

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 Black Brown Red Orange Yellow 1 2 3 4 Green Blue Violet Gray White 5 6 7 8 9

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”.

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