UoM: question about units

I would like to extend the usage of UoM based channels and I am not sure if all units are already present or if I am using them correctly.

If some of them are missing ones, I will create a PR to add them.

The description should describe “what” is my use case and the notation unit.

Description Class.Constant Quantity Comment
temperature:
°C
SIUnits.
CELSIUS
Temperature Correct?
humidity:
% rH
SmartHomeUnits.
PERCENT
Dimensionless Shouldn’t this be different from a dimensionless percent value and a “percent relative humidity”?
CO2:
ppm
SmartHomeUnits.
PARTS_PER_MILLION
Dimensionless I assume this is correct, but isn’t there any quantity? As it is about carbon dioxide isn’t it a “specific” ppm?
pressure:
Pa
SIUnits.
PASCAL
Pressure Correct?
flow:
m³/h
SmartHomeUnits.
CUBICMETRE_PER_HOUR
VolumetricFlowRate Correct?
rotational speed absolute:
rpm
SmartHomeUnits.
ONE
Dimensionless Shouldn’t there be a unit using quantity e.g. “frequency”?
rotational speed relative:
%
SmartHomeUnits.
PERCENT
Dimensionless Shouldn’t there be a unit using quantity e.g. “frequency”? In this case relative is not a relative movement e.g. angle but the speed in percent of its max. speed.

temperature:
°C SIUnits.
CELSIUS Temperature Correct?
Yes

|humidity:
% rH|SmartHomeUnits.
PERCENT|Dimensionless|Shouldn’t this be different from a dimensionless percent value and a “percent relative humidity”?

No, a percentage has no dimension

CO2:
ppm SmartHomeUnits.
PARTS_PER_MILLION Dimensionless I assume this is correct, but isn’t there any quantity? As it is about carbon dioxide isn’t it a “specific” ppm?
Same as above

pressure:
Pa SIUnits.
PASCAL Pressure Correct?
YEs

flow:
m³/h SmartHomeUnits.
CUBICMETRE_PER_HOUR VolumetricFlowRate Correct?
Yes

rotational speed absolute:
rpm SmartHomeUnits.
ONE Dimensionless Shouldn’t there be a unit using quantity e.g. “frequency”?
Yes there should

rotational speed relative:
% SmartHomeUnits.
PERCENT Dimensionless Shouldn’t there be a unit using quantity e.g. “frequency”? In this case relative is not a relative movement e.g. angle but the speed in percent of its max. speed.
As you say, this this a percentage, therefore no dimension

Thank you for your answer. But could you add a little bit more information “why” it is that way instead of only validate the current implementation?

That the provided percent unit is dimensionless is true, but the question is shouldn’t there be a difference by a dimensionless quantity and a quantity for humidity (so between “%” and “% rh”)?

The quantity interface is described that way:

Represents a quantitative property of a phenomenon, body, or substance, that can be quantified by measurement. Mass, time, distance, heat, and angular separation are among the familiar examples of quantitative properties.

Why is there no quantity for humidity? Isn’t this a quantitive property that could be measured?
I can give you the humidity in “% rH”, not only in percent. Isn’t the rH that important point to describe the quantity?

Why is there no unit for humidity similar to temperature?

The same is true for parts per million.
A lot of quantity can be measured by parts per million but why isn’t there quantity for carbon dioxide?

Because there is not SI unit involved. It’s only a percentage
Same goes for ppm

Not mathematically - “miles of railway” doesn’t imply we should invent a new unit to distinguish from “miles of road”.
Put another way, your rH is the context for a use of percentage, but doesn’t describe anything about the unit of measurement itself. Using instead with “% power” or “% speed” shouldn’t require inventing new units.

They didn’t make this approach up just for openHAB - see JSR385

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