Gas measurement unit in a rule

[Constantinos_Contis]

i measure my natural gas consuption using a pulse sensor attached to my meter.1 pulse is giving me a 0.01 m³.So i made that rule to set a counter for my gas

Number:Volume Total_gas "Total_gas" 

rule "Gas_sensor"
when
    Item Gassensorpulse changed
then
    var  gas_unit = Total_gas.state as Number + 0.01
	Total_gas.postUpdate(gas_unit)
end

that way it works but i get a plain number without a unit (m³).What do i have to change to convert the number to a number with a unit?

[rossko57]

You could change your Total_gas Item to a suitable quantity type Item - a Number:Volume perhaps.

Units Of Measurement

Then you’d need to handle it differently in your rule, something like
... + 0.01 | m³

Working with Number:Temperature Items in rules

openHAB provides Quantity Type features, which can seem baffling. On top of that, Temperature type Quantities have a few quirks all of their own. These notes intend to guide the rules author. I’ve shown work examples in DSL rules language, see below for other scripts examples. All have similar features, if different syntax. Knowing what can be done is half the battle. What is a Quantity Type? Simply, Item states and rule variables may contain Quantities - that just means a number AND a unit …

[Constantinos_Contis]

@rossko57

You could change your Total_gas Item to a suitable quantity type Item - a Number:Volume perhaps

it is already Number:Volume
i added the | m³

rule "Gas_sensor"
when
    Item Gassensorpulse changed to CLOSED
	or
	Item test changed
then
    var  Number gas_unit = Total_gas.state as Number + 0.01 | m³
	Total_gas.postUpdate(gas_unit)
end

but not changed

2022-02-15 15:00:11.800 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Total_gas' changed from 5718.62 to 5718.63

[rossko57]

@Constantinos_Contis

it is already Number:Volume

Then

@Constantinos_Contis

Total_gas.state as Number

is not a smart thing to do with it, destroying its “quantity flavour”.
var Number gas_unit = ...
and here you’re asking for the result as non-quantity too. In general, just let the system sort that part out.

This should be fairly bombproof
var gas_unit = Total_gas.state as QuantityType<Volume> + 0.01 | m³

but you might have a problem with your starting value

@Constantinos_Contis

Item 'Total_gas' changed from 5718.62 to 5718.63

which seems to have no units to begin with.
I suppose that’s a leftover from previous attempts.
I suspect this might get you out of that hole -
var gas_unit = 0.01 | m³ + Total_gas.state as QuantityType<Volume>
as it usually gives the result in the units of the first operand