How to Check Continuity in a Long Wire (Step-By-Step Guide)

In this article, I’ll teach you how to check Continuity in a Long Wire so that you can verify if your long wire has a continuous electrical path.

As an electrician, I use digital multimeters daily to check the continuity of various wires and other conductors, so I have a few tips to share. A continuity test helps you identify the actual fault in a circuit or device by telling you whether or not the wire is creating the problem.

The process of checking the continuity of a long cable is pretty straightforward.

  • Tune the multimeter to the ohms settings (at 200 ohms)
  • Plug the red probe in the socket with V next to it
  • Insert the black (negative) probe in the COM socket
  • Ping the probe leads together to check continuity between multimeter probes
  • Switch the power off and disconnect appliances
  • Touch the probes on both ends of the long wire
  • Readings (display unit) close to zero means the wire is continuous
  • If you get one or OL as the reading, your wire is not continuous

I will cover more details below.

What you Need to Check Continuity of Long Wires

Multimeter

Digital multimeters are the best multimeter to use. Instead of a needle pointer for readings, it has a display unit where the figures pop up. However, if you cannot get a digital multimeter, just use an analog one.

Wire Strippers

Getting Started

Now, follow these detailed steps to check if your long wire has a continuous electrical path.

Step 1: Understand the Basics

Knowing the color codes of electrical wires is vital. An electrical wire conducts electricity, but it also doubles as a resistor. Then, understand that the resistivity of wires varies according to length, thickness, and type or size.

Electrons collide with the conductor ions while flowing through a wire. The collision produces resistance to the flow of electrical current.

Long Wires

The collision of electrons and conductor ions in longer wires is more frequent than in shorter wires. The collision frequency of electrons and ions in a wire varies linearly with resistance. So, resistance in long wires is high.

Step 2: Set the Multimeter to Continuity Test Mode

Assemble and set your multimeter well before testing continuity to get plausible results.

Settings Configuration – Continuity Test Mode

Select the continuity option by setting the selection knob to Ohms position.

Resistance is measured in ohms, so the device must be tuned to Ohms resistance.

Display Unit

After setting the multimeter, ensure the display unit reads OL (open loop – the highest measurement), except for faulty wires.

Probe Leads

The multimeter has two probe leads; the negative lead (black) and the positive lead (red).

Insert the negative probe lead in the port labeled COM (common). Then, insert the positive probe lead in the socket labeled V(Ohms)

Verify if they are plugged into their respective sockets properly. You may ping them together as shown below:

Note: It is worth mentioning that newer multimeters have contact points instead of COM sockets or ports.

Step 3: Detach the Ends of the Long Wire

This is a valuable safety procedure you cannot miss in any continuity test. Here is how:

Switch off and unplug any connected motorized appliance. Also, disconnect other electrical devices like laptops & desktops, TV, and air conditioners. Generally, remove every component connected to the circuit. This way, you will ensure their safety in the event of an electrical fault triggered by the continuity test. (1)

Turn off the power supply to the wires you are working on. You can do it at the breaker panel. If you are unsure which breaker unit to flip off, consider turning off the main power supply to the entire household or facility.

pointing at a breaker panel

The breaker is usually located on top of the electro panel. Flip it off to avoid working with live wires, especially if you are a beginner. I recommend even professionals: switch the power off before performing a continuity test.

If you have a circuit box in the house, turn off the power by pulling the main disconnect or removing the fuse block.

Turn off a particular circuit as follows:

  • Unscrew an individual fuse
  • Avoid joining the circuit or wires and other connections.

Set your multimeter in continuity test mode. Connect the probe leads. Make sure the power supply is off. Now you can begin the test.

Step 4: Continuity Test

A 200 ohms range is the recommended ohms setting for long wires. The ohms range is vital in determining resistance, so you can use low ohms setting values for short wires.

If your multimeter has a sound feature, don’t ignore the beeps when checking continuity. Listen to the multimeter closely because any beep signifies continuity (the absence of resistance in the wire under the test), which means your wire has a continuous electrical path.

For a dead circuit, take out the wires and insert both probe leads in the multimeter jacks. That way, the probe leads won’t be attached to each end.

TEST

Strip off the insulation from both ends of the wire to about 1/2-inch depth, and touch the probe leads on the two ends of the wire (the wire doesn’t have polarity, so the order of placement is no issue).

Readings Analysis

Check the display unit for the readings and interpret them as follows:

Values Close to Zero

There is power continuity between the probe leads. Besides proving a continuous electrical path in the wire, the circuit is complete.

Unity Value – 1

If the multimeter displays one (1), there is no continuity in the wire. The continuous electrical path is broken. Such wires cannot transmit electrical current; replace them.

The Concept of Continuity

In electrical engineering, continuity describes an uninterrupted flow of electrical current in a conductor, say a wire. Sometimes wires may develop faults that render the wire non-conductive or partially conductive. So, a lack of continuity in wires stops the smooth flow of amps or current from a power source or outlet to an electrical appliance. (2)

Therefore, it is imperative to know how to check the continuity of a wire to avoid confusion. You may think your device has a fault when the wires have lost continuity. Finally, you might replace the equipment and still experience the same issue.

Take a look at some of our related articles below.



References
(1) TV – https://www.history.com/news/who-invented-television
(2) electrical engineering – https://www.topuniversities.com/courses/
engineering-electrical-electronic/guide

Video Reference

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.