Traditional resistors have colour-coded bands on them that can be added together to let you know the resistance. However, if you don’t have access to the internet to decode what the colours mean, or just dozed off during that high school science class, this guide will show you how to determine their resistance using a multimeter.
If you don’t already own a multimeter, you can pick one up quite cheaply from most hardware stores and online retailers, like Rapid. Websites like this can be a good resource for electricians who are required to use multimeters and capacitors on a daily basis.
Once you have your multimeter, switch it on and turn the dial around to the 20k? setting. Take the two probes and press them lightly against the metal legs of the resistor; small components and the circuit board can be quite fragile, so it’s important that you don’t apply too much pressure.
At this point, the multimeter will display one of three things:
- 1 / OL – If the screen of the multimeter is displaying a ‘1’ or ‘OL’, it simply means that the device has overloaded. Don’t worry, you simply need to readjust the dial to a higher setting like 200k? or 2M?.
- 0.00 – Alternatively, if the multimeter displays ‘0.00’, then you’ll be required to lower the dial, so that it is in the correct range to measure the resistance. You may need to set it to 2k? or 200?.
- If you’ve done everything right, you should get a three digit number that displays the correct resistance. 5.50 will equate to a 5.50k? resistor, or 5,500 Ohms. Be aware that you’re measuring in the 20k? setting, so you need to move the decimal place down by three digits.
It’s important to know that measuring resistance can be a difficult exercise. Environmental factors such as temperature and nearby components can affect the recorded measurement you receive. There is also a five per cent tolerance within most multimeters. This means a 5k? could measure between 4.75k? and 5.25k?.
For further information, and to watch a video guide that explains the step-by-step process, visit Adafruit.