Labeling Scientific Data

Having been working these days on a new type of interface based on electromagnetism, I had to use in several occasions a Gaussmeter (a.k.a. magnetometer) in order to measure the strength of magnetic fields.

I used the Gaussmeter in the picture above from AlphaLab Inc. but I found at first difficult to decipher the meaning of one of the labels used for the knobs. The label for the left knob states "off" to indicate that the device is off, "19,999" to indicate a low precision reading useful for large magnetic fields, "1999,9" to indicate a high precision decimal reading preferred to measure small magnetic fields. The labeling also tell us that, because of the limited number of characters that can appear on the screen, the first option will be able to display results up to 19999 G (Guass) and the second option up to 1999 G.

The problem that I had with this notation is that using the number "19,999" and "1999,9" to exemplify the "low res / high res" is not very intuitive or informative. In fact, it actually implicitly delivers the idea that the unit scale will shift of 10, weather instead is only a matter of representation: a 12 recorded with the first option might be something like a 12.4 on the second option, but the unit is always the same one. This is an obvious finding if you play with the device, but quite confusing at a first glance.

A better option could have been to write down the unit of measure ("Up to 19999G" and "Up to 1999,9G"), or not changing the scale of the values ("1G" and "1.0G"), or using descriptive text ("Coarse" and "Precise"), or simply getting rid of the distinction (as it seems the new models do). Bottom line: scientific devices should always carefully label their data, always including the unit scale of their measurements.