Buying Measurement Tools Without an Engineering Degree: A Purchasing Manager's FAQ

I'm the admin buyer for a mid-sized industrial company. I don't have an engineering degree, but I've placed enough orders for gauges, transmitters, and test tools to know what trips people up. I manage instrument purchasing for our maintenance and engineering teams—roughly $80,000 a year, give or take, depending on what breaks. These are the questions I get asked most: by coworkers, by new vendors, and by me when I took over purchasing in 2020.

• What's the difference between a pressure gauge and a differential pressure transmitter?
• How do I find the right Ashcroft product in the catalog?
• When is an inside micrometer set worth the money?
• Is the 83 multimeter still a good choice for our technicians?
• How does a FLIR thermal camera work?
• What should I check before any instrument order?
• What makes a vendor trustworthy?

1. What's the difference between a pressure gauge and a differential pressure transmitter?

This one comes up all the time because they both start with "pressure" but solve different problems.

A pressure gauge tells you the pressure at one point—like inside a vessel. You read it on-site. A differential pressure transmitter measures the difference between two points and sends that reading as an electrical signal (usually 4–20 mA) to a control system.

So when do you need which? I ask our maintenance lead. If they need to see the pressure while standing at the equipment, a gauge works fine. If they need to monitor it from the control room—or watch for a pressure drop that signals a clogged filter—that's a transmitter job. The Ashcroft differential pressure transmitter is our go-to because the range is adjustable in the field, which saves us a return order when the engineers revise their assumptions mid-project.

The thing I check before ordering: the output signal. Get that wrong and you're not just swapping a part—you're reconfiguring the control loop. That's an expensive mistake, and I made it once. Never again.

2. How do I find the right Ashcroft product in the catalog?

The Ashcroft catalog is big. Like, seriously big. Hundreds of pages covering pressure gauges, transmitters, switches, thermometers, diaphragm seals, and flow instruments. When I started in this role, I would dig through it for an hour just to find one part number.

What actually helped: asking our local distributor for a 30-minute walkthrough. Nobody had ever asked them, which surprised me—it's free. They showed me the searchable version of the Ashcroft catalog online and shortcuts I'd missed, like using the application index (i.e., identifying whether you're measuring with a direct mount or a remote seal).

You can narrow most of your options with three specs: connection size, pressure range, and enclosure rating. If you can answer those three, the catalog stops being intimidating.

One thing I should mention: the catalog also lists accessories like manifolds and snubbers. I skipped that section for a year until a field engineer told me the correct manifold can double the lifespan of an instrument in some setups. Worth checking while you're already in there.

3. When is an inside micrometer set worth the money?

When you need to measure holes, bores, or slots—anything where the outside faces aren't the dimension that matters.

We bought a 2–6" inside micrometer set in 2022, right after we started doing motor rebuilds in-house. It cost around $600. Maybe a bit more with shipping, I'd have to check the invoice.

The lesson I learned the hard way: cheap sets are false economy. I almost ordered a no-name brand to save $100. The calibration readings were inconsistent and the rods didn't seat evenly. Our quality person asked to see traceability and I couldn't provide a documented chain. That's when I learned the difference between "comes in a nice box" and "you can prove what it measures." We returned it and bought a proper set with a calibration certificate traceable to NIST.

Also, get one with a friction thimble. It sounds like a small detail until your thumb slips mid-measurement. Then it's the difference between a reading you trust and one you redo three times.

4. Is the 83 multimeter still a good choice for our technicians?

You mean the Fluke 83? Still a workhorse. Our electricians prefer it for motor troubleshooting because it handles true-RMS measurements, CAT III environments, and the occasional drop from a ladder.

The price hurts—that's real. But here's the math: we were buying $40 multimeters every few months because they died or gave readings nobody trusted. Since switching to the 83, we haven't replaced one in three years. The total cost of ownership is lower, even without doing the formal spreadsheet.

Dodged a bullet on that order. I was ready to approve the budget option when one of the electricians asked to see the spec sheet. He pointed out the accuracy rating wasn't good enough for the motor tests they were running. A good catch—one click away from ordering the wrong tool.

5. How does a FLIR thermal camera work?

The shortest version: it sees heat, not light.

Every object emits infrared radiation, and the amount depends on its temperature. The camera's sensor detects that radiation and maps it to colors— different temperatures show as different colors on the screen.

The part people don't expect: emissivity changes everything. Polished metal barely emits infrared; it reflects it. So if you aim a thermal camera at a shiny pipe, you might be seeing the heat of whatever's behind you (or the operator's hand) instead of the pipe itself. That's not a camera defect, that's physics.

We use a FLIR camera for scanning electrical panels for hot spots. But I keep my limits clear: when it's a critical reading, I call a thermography contractor. They know how to correct for emissivity, distance, and ambient reflection. A $3,000 camera doesn't replace ten years of experience interpreting images. Different tools, different experts.

6. What should I check before any instrument order?

Verification. Documented traceability. When the micrometer arrives, does it come with a calibration certificate? Is the transmitter's factory test data in the box? Is the manufacturer identified clearly on the label?

Precision instruments without documented provenance are just expensive guesses. I learned that one the slow way—and it cost me a conversation I'd rather not repeat with our quality manager.

Also, check certification dates when the box arrives. A gauge that sat in a warehouse for 18 months between calibration and delivery doesn't have "fresh" accuracy. Good suppliers note this on the invoice. Great suppliers ask if you want the calibration extended before shipping.

7. What makes a vendor trustworthy?

The ones who tell us what they don't do.

A few years back, a supplier told us outright that their differential pressure transmitter wasn't right for one of our older systems—and pointed us to a different approach entirely. They lost that sale. They've also earned every order I've placed with them since.

Under FTC advertising guidelines, claims have to be substantiated—backed by evidence. I've adopted that as a purchasing rule, too. If a vendor makes a bold claim, I ask for the test data. Show me the sheet and we're in business. Just say "trust me" and I'll keep looking.

Specialists know their limits. That's why we buy Ashcroft for pressure and temperature—that's their lane—and why I call in specialists for thermal imaging and electrical measurement. I'd rather work with someone who understands their boundaries than a generalist who overpromises. That's the lesson that's saved us the most money over the years.