CHAPTER 9 ■ RESISTORS
If your meter is displaying 0L or some very large number, double-check the setting you’ve chosen on
the dial. Is it ohm? Is the range more than 100? Wiggle the test probe connections to make sure everything is
firmly connected. Check the colors of the resistor again; perhaps your third band isn’t brown (times 10)?
A resistor that’s undergone aging, temperature extremes, shock, or other abuse may be damaged out of
the expected value. However, it is really unlikely that a fresh, 5% tolerance, 100 W resistor would be beyond
the appropriate 95 W to 105 W range. You can always try a few other resistors to be sure.
Experiencing Resistance Ranges
- Find a 470 W resistor. The color bands are yellow, purple, brown, gold.
- If you have a manual-ranging multimeter, choose an ohm range below 470 on
your meter. We’re goofing around for a minute here. - Hook up the 470 W resistor as you did the 100 W resistor (refer back to Figure 9-6).
Unlike an improper voltage range, choosing too low of a maximum range on the ohm-portion of the
dial does not harm your multimeter at all. However, the manual-ranging meter will be unable to display a
measurement of the resistance. On my meter, 0L is displayed instead of the proper value (see Figure 9-8).
Figure 9-7. Meter displaying resistance of approximately 100 W
Figure 9-8. The resistor value is above the selected range on the multimeter
This is one of the annoying aspects of a manual-ranging meter. In order to determine the resistance of
something, you either have to make an educated guess (by looking it up in a color-code table) or you have to
flip through the ohm ranges on the dial until you get a reading.
Because of the need to constantly try different ranges on the dial of a manual-ranging meter, it’s more
difficult to sort a box of resistors. That same task is a breeze on an autoranging meter.
If you have an autoranging multimeter or have now chosen the correct range on your manual meter,
you may find that your meter displays the value of the 470 W resistor as 0.470 kW more or less
(see Figure 9-9). This value is still correct. The k stands for 1000. If you multiply 0.47 by 1000, you’ll get 470.