The README for the Open MicroManipulator has a parenthetical I wish more documents had. The device moves in steps as small as 50 nanometers, and then, mid-sentence: “Please mind the difference between resolution and accuracy. The absolute accuracy is significantly worse.”

That’s the whole trick of measurement instruments, said in one breath. It can tell two positions apart at a scale smaller than a wavelength of visible light. Whether it’s standing where it claims to be is another question. A ruler with a thousand tick marks and a bent frame has superb resolution.

How it gets there is the part I liked. The motors are ordinary off-the-shelf steppers. The encoders are cheap magnetic ones, which aren’t fine enough on their own, so the designers use what they call magnetic gearing to stretch the resolution by a factor of 30. The sub-micron precision comes from cleverness stacked on cheap parts, not from expensive ones. Then the joints are tiny ball joints in a parallel arrangement, which makes it stiff enough that the cleverness doesn’t wobble.

It’s meant for lining up optics and poking at electronic components under a microscope, work that used to need a lab budget and now needs a 3D printer and some patience.

I keep thinking about how that distinction travels. Meta pulled the word “train” out of its new terms this week, which sharpened the label considerably. Whether it changed what the terms permit is, according to the legal experts, a separate matter. Resolution went up. I’d want to measure the accuracy.

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