How to Use a Multimeter to Test Voltage: A Purchasing Manager’s Checklist

It’s 8:45 on a Tuesday. One of our production lines just dropped. The maintenance tech is on another floor. The operator looks at you and asks, “Is there even power at that connector?” You’re the person who ordered the LAPP EPIC components, the enclosures, the cables—maybe the exact part number 53111420 sitting in a cabinet nearby. And you have no idea how to answer.

This is a guide for the non-engineer who ends up doing purchasing and has to make a quick decision. I’m an office administrator at a 120-person company. I manage roughly $125,000 a year in industrial parts across 8 vendors, and I report to both operations and finance. I’m not an electrician. But I’ve learned how to use a multimeter to test voltage, and you can too. Here’s the checklist I use.

Who This Checklist Is For

If you’re in procurement, admin, or any role where you’re the one ordering cables and connectors, but you don’t have an EE degree—this is for you. It’s for those moments when you need to verify whether the power is actually present before you start replacing parts. It’s also for the times when a supplier delivers a so-called “complete” assembly and you want to catch a simple wiring error before it shuts you down.

I didn’t always think this way. In 2022, I trusted a vendor’s promise that a specific cable assembly would work. They couldn’t provide a proper invoice, finance rejected the expense, and the cable itself turned out to be miswired. That mistake taught me to verify things myself, even if it’s just a basic voltage check.

Step 1: Pick a Safe Multimeter

You don’t need an expensive lab instrument. But you do need a meter rated for the levels you’ll touch. Look for a CAT rating on the body. For most shop-floor voltage checks, CAT II or CAT III is what you want. Per IEC 61010-1, CAT III meters are suitable for distribution-level circuits. A decent brand-name meter with auto-ranging costs around $80–$120 (as of January 2025).

Before you plug anything in, inspect the test leads. I once found a set of leads where the insulation was split right where the probe meets the wire. A coworker said, “It’s fine, it still works.” I didn’t use it. He did. The meter read okay, but the shock he got was not okay. (He was fine. The lead wasn’t.)

Step 2: Set the Dial to Voltage, Not Amps, Not Ohms

Most industrial circuits are either 24V DC for controls or 120V/230V AC for power. Check the nameplate or the schematic if you’re not sure. On a multimeter, select the V⎓ (DC) or V~ (AC) mode, and if your meter has manual range, pick a range above the expected value—say 200V AC for a 120V circuit, or 400V DC for a 24V DC rail. Auto-ranging meters handle this for you.

Here’s the mistake I see more often than I expect: someone leaves the probes in the 10A jack, then tries to measure line voltage. The meter is set to voltage, but the probes are in the current jacks, which shorts the circuit. Spark, smoke, dead meter. If you’re using a meter from a drawer, check where the red lead is plugged in before you connect to anything.

Step 3: Connect the Probes Correctly

Black goes to COM. Red goes to the VΩmA jack. For DC, red touches the positive side, black touches negative or ground. For AC, polarity doesn’t matter.

In a connector like the LAPP EPIC series (the LAPP 53111420 is a common enclosure part number, but the same idea applies across the line), you’ll often measure at the terminal points inside the hood or housing. Make sure the insert is correctly aligned and the enclosure is properly seated. If you’re measuring a cable gland or an external connector, check the pinout on the LAPP datasheet first.

Also: hold the probes by the insulated handles. Don’t grip the metal tip. This sounds childish, but when you’re leaning over a cabinet and the phone rings, it’s easy to slip.

Step 4: Take the Reading

Touch the probes to the measuring points, wait a second, and read the display. For AC voltage, the reading is RMS, which is what equipment is rated against. A 230V line might read 232V or 228V. That’s normal. If you’re seeing 0V or something very low, don’t immediately assume the connector is bad.

Ask yourself:

• Is the breaker on?
• Is there a fuse inline?
• Are the connector contacts clean and fully mated?
• Could the meter be measuring on the wrong range?

If you’re measuring a LAPP EPIC power connector and you get nothing, you might need to open the enclosure and inspect the wire terminals. I’ve seen cases where a screw terminal wasn’t tightened enough inside an enclosure, and it only showed up as a voltage drop under load. The multimeter showed normal at idle, but the device couldn’t start. A simple torque check solved it.

Step 5: Verify Your Meter on a Known Source

Here’s the step almost everyone ignores. Before you trust a zero reading, test your multimeter against a known source. A fresh 9V battery works for DC. A wall outlet works for AC (if you’re careful). Your meter should read close to expected.

In 2023, I was diagnosing a new machine and measured only 2V on a supposedly 24V DC input. I almost ordered a replacement power supply—until someone suggested checking the meter battery. The 9V inside the multimeter was nearly dead, and the meter couldn’t work correctly at that low voltage. We replaced the meter’s battery, and the reading jumped to 23.8V. The machine worked. That was an hour of avoidable downtime, and I learned a lesson I won’t forget.

(Mental note: check the meter battery first. I really should add that to the checklist.)

Step 6: Write It Down

A voltage reading isn’t useful if you don’t record it. I keep a simple spreadsheet with the date, part number—like LAPP 53111420—the measured voltage, and the location. When the maintenance team later asks why we replaced something, I can pull up the data. It also helps during audits. It shows that we have a habit of verifying incoming components, not just assuming they’re fine.

This documentation also gives internal customers confidence. When I tell an engineer that a LAPP enclosure arrived intact and measured correct voltage, it’s not just opinion—it’s recorded.

Common Mistakes to Avoid

Some additional cautions from things I’ve seen around our plant:

• Don’t switch the dial while the probes are connected to live terminals. You can arc the contacts and wreck the meter.
• Don’t use resistance mode to measure voltage. It might not damage a modern meter, but it gives you a garbage reading and confuses everyone.
• Don’t trust a brand-new component if you don’t buy from a reliable source. Counterfeit industrial connectors exist. A multimeter can show you that the electrical path is open, but it won’t tell you about harmful materials. That’s why we stick with established brands like LAPP.

Why Certainty Is Worth Paying For

Let me bring the whole circle back to the “cheap vs. trusted” question.

We once ordered a batch of “compatible” connectors from a vendor we didn’t know. The price was 15% lower than the LAPP equivalent. The enclosures looked similar, but two of the connectors had poor tolerances. One cracked when torqued to spec, and another had a bent pin. The production delay caused by that failure cost us far more than the 15% we saved.

This is why I believe in paying for certainty. When your line is down, something that “probably works” is not good enough. The difference between a reliable supplier and an uncertain one isn’t the price on the invoice—it’s the cost of the thing that breaks when the cheap part doesn’t do its job.

I still buy based on price. But I never buy based on price alone. And I always test what I can with a multimeter.

Final Thought

You don’t have to be an electrician to learn this one skill. A basic voltage check is simple, safe if done right, and can save your team hours of troubleshooting. And if you’re the person who orders the parts, being able to confirm that power is present isn’t just “nerd stuff”—it’s part of your job.

If you found this useful, I hope you keep a multimeter in your tool kit and a reliable brand on your vendor list.