Because a digital multimeter can measure different things, you can use it in a lot of situations. This also means that when you usually use your multimeter for one application, there is a chance you’re only using a small part of the multimeter’s functionalities. One of the functions most multimeters offer is the ability to measure resistance. In short, resistance is a measurement of how easy it is for an electrical current to flow through a certain component or (part of) a circuit.
If you’ve ever tried measuring resistance, you might have come across an infinite resistance. But what is infinite resistance on a multimeter? To find the answer to that question, we’ll discuss what resistance is in more detail and then combine it with measuring resistance on a multimeter.
What is resistance?
As we already mentioned, resistance is the ease or difficulty that an electrical current has to flow through (a component of) an electrical circuit. To make it easier to understand electrical current, we should first compare it to water flowing through a pipe. The water is the electrical current, while the pipe is the component of the electrical circuit. As long as the pipe is in good condition, water flows through it without a problem. But when the pipe is partly clogged, it cannot sustain the full capacity of water.
It works the same with resistance in electricity. If a component is fully optimized for electricity to flow through, there will be hardly any resistance (although no resistance at all is technically not possible). The opposite of resistance is conductance, which is why conductors play such an important role in electricity. The power lines that you can see flow through the landscape and that are supported by high poles are conductors, as is anything else that is designed to take electricity from one point to another.
In an electrical circuit, there aren’t just conductors built in, but also resistors. Those resistors have a carefully balanced level of resistance that regulates the flow in the electrical circuit. They also make a fantastic example of why we can measure resistance. If those resistors are supposed to have a set resistance, we can easily measure this with our multimeter. While resistors made to have a set ‘tolerance’ of a certain amount of Ohms, age, and other factors can have an impact on the exact tolerance.
Here’s the basic introduction to using a digital multimeter to measure a resistance of a resistor:
What are Ohms?
In the previous paragraph, we mentioned that resistors have a tolerance of a set amount of ‘Ohms’. Ohms, also known by their Ω symbol, is the unit in which we measure resistance, the same way we use the unit ‘pounds’ or ‘kilograms’ to measure weight.
Ohms are named after the German physicist who around 1827 first thought of the idea of resistance in electricity: Georg Ohm. Resistance is now a vital part of knowing electricity, and the Ohm meter can be found on any decent multimeter. If you’re measuring resistance, you’re measuring Ohms. While for the purpose of this blog post, we limit measuring resistance to an actual resistor, there are many other applications for measuring resistance, which makes the Ohm meter one of the most used functions on your multimeter.
How do you measure ohms?
To measure Ohms (or Ω), you need a multimeter that can measure resistance. All the multimeters we feature on our website have the ability to measure Ohms. To prepare your multimeter, consult the manual for your specific model, so you know where to put your test leads. Please note that while Ohm is the basic unit of measurement, sometimes you’ll have to measure in milliohm, or mΩ, which is not a function that’s found on every multimeter.
Once you’ve prepared your multimeter and it’s turned on, put a test lead on each end of the component you want to test. In the case of the resistor, simply put one test lead on each end and read the measurement.
There are a few measurements that can pop up on your screen. Aside from the measurement you’re expecting when you’re measuring a resistor with a 1,000 Ω resistance, there are some other measurements you can see come up on your screen. One of those is OL or infinite resistance.
What is infinite resistance on a digital multimeter?
When you see the infinite resistance on a digital multimeter, it means that there is no electrical current flowing through the component you’re measuring. That makes sense, if you think back on the comparison with the pipe. When you’re measuring resistance, you’re measuring how much water flows through a pipe. A clogged pipe gives more resistance, and hence less water flows through. A fully clogged pipe that lets no water through at all has a resistance so high, it’s literally off the charts.
With electricity, it works just the same. If there is no flow, and you’re measuring resistance, the digital multimeter has to assume that the flow has been obstructed to the point that the resistance is off the charts. Therefore, unlimited resistance means that the multimeter has measured so much resistance that there is no flow left.
That doesn’t necessarily mean that the resistance is actually that high. Remember that the multimeter is measuring resistance by measuring the flow of electrical current. A lack of current could mean that a resistor is indeed giving off that much resistance, but a more common explanation for the lack of current is a broken connection or an open switch. Most of the time, reading infinite resistance on a digital multimeter is the result of a broken connection.
It is very valuable to know the ins and outs of your digital multimeter. But first of all, you need to have a great device, like Fluke 87V (see on Amazon.com) that has a lot to offer.
One of the main functions on your digital multimeter is measuring resistance. Now that you know what resistance is, how to measure it, and what to do when you read infinite resistance on a digital multimeter, you’re just a little better equipped to use your multimeter in a variety of situations. Don’t forget to browse our other articles for more information on how to best use your multimeter.