How to Test an Ethernet Cable with a Multimeter (Quick Guide)

Ethernet cables are perfect for providing a hardwired internet connection. They are much faster than a Wi-Fi connection and more reliable, connected to the same router. So, if you need a faster and more stable internet connection for your devices then you should consider an Ethernet cable. However, just like other cables, Ethernet cables can get damaged and need troubleshooting. Faulty cables provide poor internet speed or can fail to offer any internet connectivity at all.

blue ethernet cable

To test your ethernet cables, use a multimeter. Ethernet cables have a metallic part encased in a sheath or jacket. So, set your multimeter to ohms and check the continuity between the portends and plug. The resistance or Ohms value should either be zero or very little due to the resistance of the wire. If the Ohms reading is large, then you need to purchase another Ethernet cable. (1)

So, what steps do you need to follow to test your Ethernet cable? I will guide you through every step in detail below. Note that this method is very useful, especially if you do not have a conventional Ethernet cable tester.

Setting your Ethernet Cable

Before you set your Ethernet cable for testing, note the internet connection on your device. Poor signals are the primary indicators of a faulty Ethernet cable. First, check the right-hand side of your computer, on the taskbar section. Most computers will show a red ‘exclamation mark’ icon. If this is the case, then get your Ethernet cable ready for testing. (2)

To set your Ethernet cable, ensure that the portends and plugs are properly connected. Again, an unstable connection between the ports and the plugs can lead to a poor internet connection.

You can do this by separating the portends and the plug. Then reconnect them by making sure the plugs and the ports are properly linked.

Now Set your Multimeter

We will be performing a continuity test for your Ethernet cable. Continuity measures the resistance (in Ohms) of electrical conductors. Therefore, you have to set your multimeter to Ohms to do this test.

The multimeter has a selection knob with a pointer (like a handle) that is used to set it to measure various electrical properties. So, turn the selection knob to point to the Ohms reading, usually denoted by the Ω symbol.

After setting your multimeter to Ohms, plug the probes into the ports as follows. Just plug the black probe (ground connection) into the port labeled COM and the red probe into the port with a V label net to it.

You can ping the probe leads together to check if the multimeter is working. Most digital multimeters will beep if they are in optimal conditions.

Now Let’s Test an Ethernet Cable

So, you have your multimeter, and the Ethernet cable ready for testing. Proceed as follows to verify continuity for your Ethernet cable:

  1. Clamp your Ethernet cable ends together using the leads. You may attach alligator clamps, or sewing needs to the end of the meter leads.

  1. After securing your Ethernet cables and attaching the sewing needles to the meter leads, connect the needles to the Ethernet cable ports. Connect both probes (fastened to the needles) to the Ethernet cable ends – the port terminals.

  1. Check the display unit. You will get a zero or small reading for well-functioning Ethernet cables. If the display reading is high, your cable is faulty or damaged. You need a new one.
  2. Do the testing for all the terminals on the two ports with various labels. Ensure that you do it simultaneously, as each probe needle goes to the respective port terminals. You need to place a black probe needle on the terminal A of port 1, and then place the other probe needle on terminal A on port 2.
  3. Note all the readings. Any high reading shows discontinuity on that port terminal you are testing.

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References
(1) Ethernet – https://www.networkworld.com/article/3657734/what-is-ethernet.html
(2) computer – https://www.britannica.com/technology/computer

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.