For the past 11 years, I’ve been the engineer who gets called when a product doesn’t measure up. I keep a running mistake log—not to feel bad about it, but because every entry has saved me from repeating the same mistake. This article is one of those entries.
In early 2024, I ordered a small run of aluminum brackets for a prototype assembly. Our electrical tests looked great; I had just added a Keithley DMM6500 bench digital multimeter to the lab and it gave me more confidence than any handheld meter I had used before. But the brackets didn’t fit. The machinist had followed my dimensions, and my dimensions were based on a caliper that had started to drift. The rework cost us roughly $1,200 and about nine days. For a small lab, that was not a rounding error.
A bench full of excellent electrical instruments won’t help you when a physical part doesn’t fit.
Hold On: What About the “Keithley Oscilloscope” Search?
Before I get into calipers, I want to clear up something that shows up in the same search: Keithley oscilloscope. If you look at the DMM6500’s touchscreen and graphing features, you can see why people type that. But Keithley doesn’t make a traditional oscilloscope line, as far as I’ve found. Keithley’s strength is precision DC and low-level electrical measurement. The DMM6500 can graph slow trends and let you watch a signal drift over time, but it is not meant for high-speed scope measurements. If you need megahertz waveforms, buy an actual oscilloscope. If you need low-current or low-voltage measurements with bench-level accuracy, the DMM6500 is the more relevant tool.
Why a 6-Inch Digital Caliper?
Most of my measurements are on PCBs, brackets, standoffs, and connectors. A 6 inch digital caliper covers up to 150 mm, and it fits comfortably on a crowded bench. An 8-inch or 12-inch model is helpful when parts are bigger, but for daily electronics work, the 6-inch tool gets used far more.
Starrett vs Mitutoyo Calipers: What I Compared
I tested the Starrett 797B and the Mitutoyo 500-196-30, both 0–6 inch, both with 0.0005 in / 0.01 mm resolution. I did not run a laboratory-grade comparison; I am not a calibration technician. What I can tell you from a test-engineering perspective is how they behaved during three weeks of real work.
Slide and Jaw Feel
Everything I’d read made this sound like a coin flip. It wasn’t for me. The Mitutoyo’s slide moves more freely, which makes it easier to close the jaws with consistent force. The Starrett has more resistance in the slide, and its lock feels more positive. I originally leaned toward Starrett because of its reputation. My hands disagreed after about 20 minutes. I still like the Starrett when I need to lock a reading and carry it away from the part. For bench measurements, I prefer the Mitutoyo.
Conclusion for this dimension: Mitutoyo for repeated bench readings; Starrett for lock-and-carry inspection.
Display and Controls
The Starrett display felt larger and easier to read from slightly unusual angles. The Mitutoyo zero button is positioned more naturally for one-handed use, and I could zero it without shifting my grip. Both have clear digital readouts, but they suit different workflows. If you are at a bench measuring parts all day, the Mitutoyo control layout is easier. If you are holding a caliper up near eye level or in awkward positions, the Starrett is easier to read.
Conclusion for this dimension: For our lab, one-handed operation matters more than display size. For someone doing QC in tight spaces, I would not argue with choosing Starrett.
Repeatability and Calibration
This was the boring dimension. Both calipers zeroed consistently on the same gauge block. Both gave repeatable readings when I measured the same bracket repeatedly. Neither clearly outperformed the other. That is the point: at this level, accuracy is not the main differentiator—your measurement routine is. A $200 caliper can still mislead you if you never check zero before a critical session.
Conclusion: No clear winner on raw accuracy, but a clear action item: verify your zero and use a known standard before trusting any dimension.
Price, Support, and Small-Order Friendliness
I ordered only one unit of each, and neither distributor made me feel like my order was too small. That matters. I have been on the other side of that conversation with other suppliers, and it is not pleasant. Both companies answered a calibration question, supplied the paperwork, and did not push unnecessary extras. Today’s one-caliper order can become next year’s ten-caliper order. A supplier that ignores small customers is making a short-sighted choice.
Conclusion: Both brands treated a small lab properly. If you are a small team, don’t accept less from anyone else.
Where the TG267 Thermal Camera Fits
After the caliper lesson, I started questioning my other blind spots. That led me to buy a FLIR TG267 thermal camera. I had thought thermal imaging was a nice-to-have, something for facility maintenance rather than electronics troubleshooting. Then we had an intermittent high-current failure. My Keithley DMM6500 measured it perfectly—it saw the extra current appear late in the evening. But it could not tell me where the current was going. The TG267 showed the problem in about twenty minutes: a small component was heating up just before it failed.
I’m not saying the TG267 is a replacement for the Keithley DMM6500, or that it answers the “Keithley oscilloscope” question. It answers a different question: where is the energy going? A DMM tells you the value; a thermal camera points you to the guilty area. Both belong on a small budget.
Bottom Line: What I Would Buy Today
If I were rebuilding my small lab setup now:
- First electrical tool: a Keithley DMM6500 bench digital multimeter, or the Keithley model that matches your low-level measurement need. Do not spend months chasing noise when a proper meter would make the problem obvious.
- First mechanical tool: a 6-inch digital caliper from Mitutoyo for daily bench work, or a Starrett 797B if you prefer a more positive lock. Check zero against a standard before every serious measurement session.
- If you troubleshoot prototype boards: add a TG267 thermal camera before you pay someone else to find the hot spot for you.
Which caliper stayed on my bench? The Mitutoyo. The Starrett is not a bad tool—it lives in my drawer for inspection work. But if someone tells you Starrett is superior just because of history, ask them to measure 40 brackets in a row. My measured conclusion: brand loyalty does not replace a good repeatability routine.
And for the “Keithley oscilloscope” searches: choose the instrument based on what signal you are trying to see, not just a brand name. If the problem is low-level DC, get a Keithley DMM6500. If the problem is a fast waveform, get a real oscilloscope. If the problem is finding which component is heating up, let the TG267 do the hunting. Three different jobs, three different tools—and now I trust all of them enough to document the results.
