3 Replies Latest reply on Sep 25, 2017 10:52 PM by salesm21

    Resistor Confusion

    salesm21

      Help me,

      I am currently frustrated with how my night of sorting resistors is going. I have 5 band resistors and cant seem to get my Multi meter to read properly. I have it set to 200 OHMS and the resistor in question color banded from the beginning 1st. green 2nd. brown 3rd. black 4th gold 5th yellow. This according to my little chart should be 51 OHMS. But my meter shows me 55.9. What am I doing wrong? 

        • Re: Resistor Confusion
          jw0752

          Hi Mitchell,

           

          You aren't doing anything wrong. You have read the bands correctly and the meter is telling you the reading that it is measuring. The resistor you are measuring has a yellow 5th band which means it is a 20%  tolerance. This means that the actual reading can be as high as 63 ohms and as low as 39 and still be within tolerance. The 55.9 that you are measuring is actually pretty good for this resistor with only a 10% variance from nominal value. This is unfortunately the reality of the world. We can put exact numbers on our calculations but nature makes it very difficult to to match reality with our projections.

           

          John

          6 of 6 people found this helpful
          • Re: Resistor Confusion
            gecoz

            Hi Mitchell,

            Adding to what jw0752 already said, you also might need to take into consideration the resistance added by the multimeter leads, if you are using them to measure the resistor's value. Good quality leads usually have a resistance of 0.5 Ohm or less, while cheap one (or corroded/damaged) can easily reach few Ohms. Usually, when measuring high value resistors, you can safely ignore the leads resistance, but when measuring low value resistors, the quality of the cables can introduce a significant offset to your reading. In your case, with a resistor of nominal value of 51 Ohm and a tolerance of 20% (+/- 10.2 Ohm), you can still probably ignore the leads as the tolerance is probably almost an order of magnitude bigger that the leads resistance. The quickest way to check how much resistance you get from the leads is to set your multimeter to the lowest resistance range and then make the probes tips touch together.

            Fabio.

            4 of 4 people found this helpful
              • Re: Resistor Confusion
                peteroakes

                What may be better is to touch the probe leads to the resistor lead ( same

                side of the resistor) . This will then include any resistance from the

                resistor leads corrosion / oxide etc. Null this out and then re check.  But

                at the end of the day. They are 20% tolerance resistors

                1 of 1 people found this helpful