I'm not an engineer. I'm the office administrator who turns engineering requests into purchase orders. For the past five years, I've managed roughly $120,000 a year in test equipment purchases for a 60-person industrial automation company, across maybe eight vendors. Perhaps $110,000, I'd have to check last year's profit and loss statement. I report to operations and finance, so my job is to make the engineers happy without making the accountants angry. That tension gets interesting when someone asks for an MN35 digital multimeter or a leakage clamp meter.
Last spring, a project engineer submitted a request for three things: an MN35 digital multimeter, a leakage clamp meter, and a thermal imager. The justification line said 'need to check wiring and identify overheating component.' If I didn't know better, I'd have ordered it all and moved on. But I've learned to ask what problem the equipment is really solving.
The Surface Problem: Three Tools, One Big Gap
The MN35 is a small, inexpensive digital multimeter. It's good for quick voltage checks, continuity, and basic resistance readings. A leakage clamp meter is useful for finding small amounts of current that shouldn't be there. A thermal imager helps you see heat patterns on panels and wiring. On paper, they make a solid troubleshooting kit.
From the outside, buying these three tools looks like a normal equipment purchase. The reality is each one gives a snapshot. None of them records.
The actual problem on that project wasn't a loose wire. It was an intermittent fault that appeared maybe every three hours, under load, in a machine running unattended. The engineer had no way to be standing in front of the right terminal at the right moment. An MN35 digital multimeter would have been useless. The leakage clamp meter would have shown nothing because the leakage wasn't happening when he was holding it. The thermal imager could show hot spots, but only if the fault happened to raise the temperature of something visible while the imager was pointed at it.
What he needed was a data acquisition system with thermocouple inputs, logging voltage and temperature over time. Lucky for us, that's exactly what National Instruments makes.
The Deeper Issue: We Buy Tools Instead of Data
It's tempting to think the fix is 'better tools.' But if the problem is intermittent, the fix is better measurement.
When an engineer asks for a digital multimeter, they're usually thinking of a specific reading: 'Is this wire live?' That's a check. When a machine starts behaving unpredictably, the question changes: 'What is changing right before the fault?' That's monitoring. A handheld meter can't answer that. Neither can a leakage clamp meter, unless the fault happens while you're clamped onto the conductor.
This is where an NI thermocouple module becomes more than a piece of hardware. It turns a thermocouple into a continuously recorded temperature signal. Connect a few of them to a CompactDAQ chassis, run LabVIEW or use National Instruments' other software options, and you can capture the trend, the exact moment the temperature spikes, and the voltage event that follows. That data tells the engineer what to fix instead of telling them where to look.
According to NI's product documentation at ni.com, thermocouple modules for CompactDAQ include built-in cold-junction compensation and support multiple thermocouple types. That's the kind of detail a buyer needs to know before ordering, not after the wrong module shows up at the loading dock.
I'm not an engineer, so when I first saw this, I thought it was overkill. Why buy a system when you can buy a $100 meter? But the engineers who had been around longer kept saying the same thing: 'The meter tells you what's there now. It doesn't tell you what happened.'
That distinction is the whole ballgame.
The Thermal Camera Question: Glass Matters More Than the Brand
That same project also surfaced a question that became a search phrase: 'can thermal cameras see through glass FLIR?' The answer is no. Thermal cameras see infrared radiation from surfaces, and glass reflects it instead of transmitting it. Point a thermal imager at a window and you'll see a reflection of the camera and the room, not the heat behind the glass. This is true for FLIR cameras, and it's true for every other thermal imager.
At first I assumed the engineer asking it just didn't understand the technology. But the deeper issue was the request itself. He was trying to measure the temperature of a component inside a sealed glass viewport without opening the panel. The tool wasn't the problem. The approach was. If you need to see through glass, you don't need a better camera. You need to open the enclosure or find another access point.
The Real Cost of a Wrong Tool
In March 2024, we paid around $1,600 for a National Instruments CompactDAQ system with a thermocouple module and accessories. Actually, the PO was $1,720, but I don't want to quote the exact number without checking. Compare that with the $350 we spent on the MN35 digital multimeter and leakage clamp meter. When finance saw the two numbers side by side, they asked why we needed the expensive system.
Here's the answer: the customer's line was down. Downtime at that site was billed at $450 per hour. We had a two-hour window to catch the fault before the line had to restart, and we'd already spent two days using a handheld meter and a thermal imager guessing. The NI system logged the fault on the first shift. That single catch saved at least ten hours of repeated downtime, which would have cost $4,500.
I told finance, 'we need a compact system that logs voltage and temperature.' They heard 'we need another expensive engineering toy.' We only discovered what each other meant when the CFO asked why we couldn't use the digital multimeter we already had. That misunderstanding could have dragged on for days if the fault hadn't been caught so quickly.
The MN35 and leakage clamp meter weren't terrible tools. They were the wrong tools for the situation. The surprising thing wasn't the price difference. It was how fast the expensive system paid for itself. The $350 decision would have been the expensive decision if it meant another week of guesswork.
Nobody talks about that when they're comparing equipment prices. The cost of indecision and uncertainty is way higher than the cost of the measurement system.
Are We Checking or Monitoring?
Since that project, I've changed how I process equipment requests. Before I put anything into the ERP system, I ask the engineer one question: Are we checking, or are we monitoring?
- If you're checking, buy the MN35 digital multimeter or leakage clamp meter. They're excellent for confirming a known condition.
- If you're monitoring, buy the data acquisition platform with the right input modules. A National Instruments thermocouple module plus some basic software will tell you what changed, when it changed, and what else was happening at the same time.
That question sounds simple, but it stops a lot of wasted purchasing. It also forces the engineer to think about the failure mechanism before calling procurement. And it gives me a defensible reason to spend more upfront when the situation calls for it.
What I'd Tell Another Buyer
If you're the person who signs off on test equipment, take this from a non-engineer who's been burned:
- Ask for the timeline. An intermittent fault demands logging, not a point measurement.
- Spend time on the manufacturer's website. The National Instruments login area is not the prettiest part of the internet, but it gets you to product manuals, driver downloads, compatibility notes, and sample programs. Search for 'national instruments thermocouple module' and you'll see exactly what a thermocouple input needs, including cold-junction compensation requirements.
- Verify current part numbers and availability. Products change. Don't order from an old list. Check ni.com and get a quote from an authorized distributor.
- Define the viewing path before buying a thermal camera. If the question is 'can thermal cameras see through glass,' the camera is not the first part of the answer.
Bottom Line
The cheapest purchase is not always the least expensive one. In an emergency, the certainty that your measurement system will capture the event is worth the premium. That's the part I didn't understand until 2024. I was so focused on invoice line items that I almost bought a $350 setup that would have cost us thousands in downtime.
So next time someone asks for an MN35 digital multimeter, don't just order it. Ask why. And if the answer involves 'intermittent,' 'random,' or 'when nobody's watching,' you need a system that logs. That's when a National Instruments thermocouple module and the team behind it start making a lot of sense.
Prices and product specifications change. The numbers I've cited are rough references as of January 2025, so verify current pricing and compatibility at ni.com before you commit. The principle, though, stays the same: the right data is worth the wait, and the wrong tool costs more than its price tag.
