[SOLVED] RPM as Quantity unit

What would be the best way to implement RPMs as a unit? Angle divided by time? Would you call it a unit of Speed or something else?

I would say rpm belongs to quantity frequency.

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It’s a conversion from Hz.
1Hz = 60 rpm

Never occurred to me that rpm would be a frequency, but makes sense. I’ll do that then. Thanks!

I think this is different to frequency. Frequency implies X cycles per time unit, but tells you nothing about the cycle. It could be on-off, or cycling rainbow colours, blah. You cannot predict where you will be in a half-cycles time.

Angular speed adds the info that actual rotation is involved. We might have rpm units, but could be degrees per hour for a telescope mount. Position is completely predictable over time.

JSR 385 UoM provides angular speed, official SI unit radians per second, but commonly used as rpm instead of course.

@vzorglub for comment

rpm means revolutions per minute. In other words 360degrees/60s. Or 1/60 Hz

Yes. You can express rotational speed as a frequency. That doesn’t mean you should, you’re throwing away the information that rotation is involved.

There’s a choice - does (or should) openHAB include angular speed among its UoM types? If so, that’s where rpm belongs.
It is part of JSR285 which I thought was basis for OH UoM

If openHAB chooses not to support angular speed, then frequency category is a suitable next best approximation for rpm.


It is the accepted common usage. I think it should be in the frequency category.

Sorry, what is?

JSR385 provides a category for rotational speed, quite separate from frequency.
SI have a unit for rotational speed, quite separate from frequency.
Use it or ignore it, I don’t get a vote.