How to Use a Multimeter: A 6-Step Cable Checklist for General Cable Distributors

I'm a procurement manager at a 45-person industrial distributor. For the past six years, I've managed our wire and cable budget—about $180,000 annually—and I've documented every order in our procurement system. I've negotiated with more than two dozen General Cable distributors, and this is the multimeter checklist I actually use when a reel shows up, whether it's a direct shipment or an inter-company transfer from General Cable's Chino distribution center.

If you're a contractor, electrician, or facility buyer who wants to know how to use a multimeter to check incoming cable, this list is for you. There are six checks. Number four is the one most people skip.

Who This Checklist Is For

Use this when a reel or box arrives from a distributor, when you're pulling cable and something feels off, or when you're comparing a new supplier. I use it especially when the order comes from the General Cable Chino facility—not because I expect a problem, but because even good warehouses make mistakes and forklift damage happens.

Actually, let me rephrase that: I don't use a multimeter to judge General Cable's reputation. I use it to judge the delivery. Even a great manufacturer can have a bad day in transit.

I also use this checklist after a failure. If a cable doesn't pass, I have documented proof before I call the distributor. That's saved me more than once.

Step 1: Set Up Your Multimeter Like You Mean It

Set the meter to resistance (Ω) or continuity mode. Before testing anything, touch the probes together. If the meter doesn't beep or read near zero, your leads are bad. This sounds too simple to mention, but it's the first thing I check when a reading looks off.

Make sure the meter is rated for where you're using it. According to Fluke (fluke.com), a meter used on industrial circuits should be at least CAT III rated. A meter without a safety rating can give you false readings—or worse, fail in a live panel.

One more thing: check the battery. A low battery can cause intermittent, incorrect readings. I've chased 'cable issues' that turned out to be a dying 9V battery.

Step 2: Read the Label Before You Touch a Conductor

I learned this one the hard way. In my first year, I assumed 'standard' meant the same thing to every vendor. It doesn't. The jacket printing and the reel label tell you the gauge, stranding, voltage rating, and whether the cable type even applies to your application. Verify that all of it matches the PO before you spend time testing.

General Cable has over 150 years of history in wire and cable, and it's now part of the Prysmian Group. That's a strong starting point. But if the packing slip says General Cable Chino distribution center, that still only means it left the building in good shape. I once caught a Cat6 reel sitting in a Cat6a box. The label saved a project.

Step 3: Continuity Test Every Conductor

Set the meter to continuity. Test each conductor end to end. For a multi-conductor control cable, label both ends and check every pin, not just the ones you plan to use. It feels repetitive, but the extra five minutes is cheap insurance.

This is where my classic rookie mistake happened. I heard the beep and assumed the cable was fine. A beep means there's a path, but it doesn't tell you the quality of the path. That's why the next step matters.

Step 4: Measure Resistance, Not Just the Beep

Switch to the lowest resistance range. If your meter has a relative or zero mode, touch the probes together and zero it out. That way you're measuring the cable, not the leads.

Now measure from one end to the other on each conductor. For a quality check, compare your reading to a known-good cable of the same length and gauge. If the suspect cable reads noticeably higher, you have a problem—a damaged strand, a bad splice, or a loose connection inside the termination. Wait, 'noticeably higher' needs a number. I'd say anything above 15-20% over the reference for the same length and temperature is worth investigating.

(For context: this is the same test I used when I couldn't get a clear phone call from a Nokia 2660 Flip. A clear phone case wouldn't have shown the problem, because the issue was inside the charger cable. If a five-foot cable can hide that, a 500-foot reel can definitely hide a bad conductor.)

Don't skip this because 'it beeped.' The beep just tells you the circuit isn't open. The resistance reading tells you whether it's healthy.

Step 5: Check the Shield and Drain Wire

For shielded cable, set the meter to ohms. Test continuity from one end of the shield to the other, and from the drain wire to the shield. Also confirm there is no short between the shield and any conductor. Use the highest resistance range for the short test; you want to see no continuity or OL between shield and conductors.

This step catches a common issue: foil shield damaged during pulling. If the shield is broken, you'll get intermittent EMC problems that are hard to trace later. I've seen that happen in an industrial plant, and the electricians blamed the drives for three days before finding the bad shield.

Step 6: Flex the Cable While Watching the Reading

This is a step I didn't always do, and I should have. Unroll a length, then flex the cable near both ends while keeping the probes connected to the conductors. If the resistance value jumps around, the conductor is likely stressed or fractured under the jacket.

In Q2 2024, this exact test caught a damaged reel before it hit a jobsite. The cable passed an initial continuity check, but when we flexed the end near the jacket termination, the resistance spiked from under an ohm to nearly 20 ohms. That reel went back to the distributor.

Looking back, I should have built this test into receiving from day one. At the time, I didn't want to slow down the process and trusted the distributor's word. The 15 minutes would have saved a 3-hour rework later.

Notes, Common Mistakes, and Where to Stop

First, know the limit of a multimeter. A standard multimeter only applies a small voltage. It's good for continuity and resistance checks, but it is not a substitute for insulation resistance testing. For insulation or hipot testing, you need a megohmmeter, sometimes called a megger. According to ANSI/TIA-568.2-D, for Cat6/Cat6a certification you need a proper field tester anyway. So use the multimeter as a gate, not a final certification.

Second, don't assume an OEM brand means the cable wasn't damaged in transportation. General Cable builds to tight specs, but a forklift can crush a reel even at the best General Cable Chino distribution center. Test before you accept the material, not after.

Third, document your readings. Take a photo of the meter with the cable ID in the background. When you're managing an annual cable budget of $180,000, a photo with resistance readings gives you leverage in every vendor conversation. It also protects your team if a customer blames you for a field failure.

Fourth, I do not recommend using a regular multimeter for insulation testing. It isn't rated for that, and the results can fool you. Keep the multimeter for what it does well: continuity, resistance, voltage presence, and basic troubleshooting.

Bottom Line

A 10-minute multimeter check costs almost nothing. A field failure costs labor, downtime, and trust. I've seen a $1,200 rework caused by one bad conductor, and I've also seen a distributor replace a full reel without arguing because the test result was obvious.

The quality of the cable you install becomes the quality of your company in your client's mind. That's why I don't treat testing as optional. It's not about being the cheapest, and it's not about over-specifying. It's about making sure the product you deliver is the product you promised.

Factor in rework and customer confidence, and the cheapest quote can become the most expensive one. If you're in a position where you control purchases, build this checklist into your receiving procedure. Your future self will thank you.