If you already know what a nonius is, you can probably skip this post. But, if like us, you would have to look it up, we’ll tell you what we found out. It turns out, a translation mistake taught us a new word and some history we weren’t aware of.

Have a look at the adjacent graphic from a waveform display. What would you call the vertical red lines at positions 139 and 200?

We’d probably call them markers. Or maybe cursors. The manual, however, calls each one a “nonius”. It refers to them that way multiple times.

Oddly, the manual also has sentences like “Select one nonius and right-click, and then select ‘Remove Marker’ in the next window to delete the nonius.”

So, clearly, a nonius is the vertical line marker or cursor. But that, of course, begs a question…

What is a Nonius?

Have you ever heard of the vernier scale? If you’ve done navigation, used a traditional caliper, or tuned an old shortwave receiver, you probably have. [Pierre Vernier] developed it in 1631 as a way to better interpolate values on a scale.

However, there was an earlier version used to improve measurements on astrolabes. A Portuguese navigator named [Pedro Nunes] created this type of astrolabe in 1542. The Latinized version of his name is [Petrus Nonius]. What are the odds of him inventing… oh wait, they named it after him. That does make more sense.

The nonius is a series of concentric circles traced on the instrument. Working towards the center, each circle has fewer divisions than the previous one. In fact, if the outer ring had 90 marks for 90 degrees, the next ring would have 89, and the following one would have 88.

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