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Use a Resistor to Test Your Multimeter

By Jestine Yong on May 12, 2012

You may have used a garden hose to water your lawn or plants. Did you notice the flow of water reducing when someone stepped on the hose? The pinching of the hose, when someone steps on it, increases the resistance of difficulty faced by the water in flowing through the hose. Consequently, the flow of water reduces.

What is a resistor

A resistance in an electrical circuit has much the same function. It impedes the flow of electrons or the current through the wires of the circuit. The wires are made of a material that has very low resistance. By replacing the wire in a circuit with a resistor, a definite amount of impedance is introduced, thereby reducing the current by a certain amount.

A resistor is measured in ohms. A one-ohm resistor, in a circuit, will allow one ampere of current to flow, when there is a potential difference of one volt across it. Several types of resistors are available, of different value and with various sizes. Some have two wires called leads sticking out from either end, while some are surface mountable with no leads. Resistors with leads are color coded for their values, while the leadless ones have their value printed on them, which can only be read with a magnifying glass.

How to read a resistor

Color-coding a resistor has the advantage of being readable no matter how the resistor is rotated. Additionally, no numbers are to be read, which makes it simpler. You only have to follow the table below for interpreting the colors, which are in either four bands or in five bands –

4-Band Code	1st DIGIT	2nd DIGIT	—	MULTIPLIER	TOLERANCE
COLORS
BLACK	0	0	0	1	—
BROWN	1	1	1	10	1%
RED	2	2	2	100	2%
ORANGE	3	3	3	1000	—
YELLOW	4	4	4	10000	—
GREEN	5	5	5	100000	—
BLUE	6	6	6	1000000	—
VIOLET	7	7	7	—	—
GRAY	8	8	8	0.1 GOLD	5% GOLD
WHITE	9	9	9	0.01 SILVER	10% SILVER
5-Band Code	1st DIGIT	2nd DIGIT	3rd DIGIT	MULTIPLIER	TOLERANCE

How to test a multimeter with a known resistor

If the valueof a resistor is known, it can be used to test if a multimeter is reading correctly. A multimeter measures the value of a resistor by feeding a small amount of voltage into it and measuring the current flow. Consequently, if the batteries of the multimeter are weak, it may not read correctly. By using two reference resistors, typically 100-ohm and a 100K-ohm, with 1% tolerance, you can check if your multimeter is reading correctly. The 100-ohm resistor checks if the batteries of the multimeter are strong enough, and the 100K-ohm resistor checks if the multimeter has other internal defects.

This article is contributed by Daniel Moeller.

By the way, if you have any short repair articles (has to be original) you can send it to me for review. If I found it to be good I will help to post it in my blog-You can put in your name or website at the end of the article-thanks.

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