How To Use A Multimeter
Many up-and-coming electricians have trouble understanding how to use the various electrical testers out on the market. All of the dials, characters, and options can get a bit confusing if you don’t have experience using a multi-meter. In this episode, I talk about how to use a commonly used tester, the Fluke T5-600.
Technically the fluke T5 is not a “multi-meter.” Fluke’s website lists it as a “tester,” while their Multimeter section shows only digital multimeters with no separate jaw-type ammeter. However, a multi-meter is simply a “multi-use meter” – something that can test several different electrical units of measure. The T5 measures voltage, amperage, resistance, and continuity. There are other multi-meters out there that have extra functions but the T5 is for the basic 4 that most electricians will use every day. So how do we use it?
What you’re doing when you’re testing for voltage is testing the difference of potential between two points. “Voltage” is a difference of potential between two points in an electrical system. It is not a reading of one conductor, it’s reading a difference between two. It can even be a difference between one wire and a piece of metal that’s bonded to earth. But keep in mind that you’re trying to get a value that shows “the difference in potential” between TWO things.
Flip the dial of the T5 to the “V” and take the leads out of the slide-in slots on the back. Ensure that you’re wearing proper PPE such as insulated “hot-gloves,” and a flash suit if you’re working in an electrical panel. Take one lead and touch it to a known hot conductor or terminal. Take the other lead and touch it to that same conductor or terminal. Notice you get a reading of 0v. This is because this conductor is at the same potential as itself. To get a voltage reading you have to test between two different objects.
Next, leave one lead on this conductor, and move the next lead to a different conductor. If you’re working in an electrical panel this can be a different colored conductor. You should notice a reading of around 240v (volts) if you’re in a single-phase panel. If you’re in a 3-phase panel you may get a measurement from anywhere around 208-240v. This means you have a difference in potential between these two conductors.
Next, leave one lead on one of the phase conductors and place the other lead on the white conductor. You should notice a difference of potential (voltage) reading of around 120-volts. This is because the neutral is the half-way point in the system, so from it to either hot conductor you should have half the potential as you do between the two hot phase conductors.
The same should happen between any hot phase conductor and the green or “grounding” conductor, as the neutral (grounded conductor) and ground (grounding conductor) are bonded at the electrical service. This means the neutral and ground should be at the same potential, as they are technically “bolted” together and touching one another.
One thing to note is that this tester is only rated for up to 600-volts. You could do some incredible damage to the tester or yourself if you use this on anything above a 600v system.
How to use the amperage setting – Flip the dial to the “A” (Amperes). Line your wire up with the two lines inside of the jaw of the ammeter. Only measure one wire at a time. This tester will give you readings up to 100 amps, so for anything more than that you’ll need a larger tester. This makes sense since the max size wire you can fit in the ammeter is 1/0 THHN. If you have larger wires than 1/0 THHN then you’ll need to get your hands on a clamp-on ammeter.
Flip the dial to the Ohm (Omega) symbol. For this you want to test on a dead circuit so make sure the power is shut off. To test a conductor’s resistance you will need to have access to the beginning and the end of the conductor. Put one lead on the beginning of your conductor and one lead and the end of your conductor. This meter will display how many ohms of resistance there is between the leads. When there is low resistance you will hear a loud toning noise. When you try testing a really high resistance the tester will stop emmiting a tone, and will instead just display values. This meter is only good for up to 1,000 ohms. Anything more than 1,000 ohms should really be tested with a megger (megohmmeter)
Continuity is essentially the same thing as resistance as far as this tester is concerned. To test the continuity of a conductor do the same thing you’d do to test resistance. When you hear an audible tone you know that the tester is sending and receiving a signal from the tester, back to the tester. This lets you know that it is finding a complete loop.
Moral of the story, not only do you need this tool in your arsenal of diagnoses, but knowing how to effectively use it can be the difference of being a helper/apprentice to becoming an actual electrician. Ultimately, a multimeter can save you a lot of time and headache instead of spending hours and hours on the same issue.
Used In This Episode:
Please check out the Electrician U Facebook page and subscribe to the YouTube Channel if you like these videos! Also check out the Electrician U Instagram page.
**Disclaimer – These videos are for training purposes alone, all work done on electrical systems should be done by a licensed and insured electrical contractor. If you are not an electrician, do not attempt any of the work you are seeing in these videos.**