LCR Meter U1733C "rn" Symbol Meaning

Question

I have the Keysight U1733C LCR Meter and when I meausure inductance shows me the "rn" letters in front of the Henry units. Do you know what it means (on the manual I found only the SI units - page 37)?

Answer 1

That's an m; the meter currently reads 782.9 mH. By turning off the "r"-shaped segment, it can also be an n, for nanofarads or nanohenries.

This type of segment reuse is very common with LCDs. There has to be a gap between segments, because otherwise you'd short them together and you couldn't control them independently, so it can be pretty visible. A less confusion-prone design might have been to have an n followed by a ר, which is less likely to be mistaken for something else.

Here's a picture showing all the segments active at once, taken from the U173xC user's guide (page 31 in the PDF, labelled page 11).

You can see in this image how they've crammed all the SI prefixes and units together in the lower right. They've even meshed the μ so it fits in between the humps of the m! It's not practical to use a full seven- or fourteen-segment display to show such a limited set of letters, so they just made one segment for each of p, μ, k, M, F, Ω, H, and S, and then took advantage of the similar shapes of m and n to combine those two together and save a little space.

The downside to this is that segments can't overlap, so you may end up with the prefix and the unit widely separated; nonetheless, it'd still be clear what is meant, so this is good enough. Notice that they arranged the prefixes and units so that the least likely combinations of unit and prefix are the most widely spaced; you'll probably measure pF a lot more frequently than you measure pH or pS, and if you're working with anything in the megafarads or megahenries, let me know where so I know to stay very far away!