Help Creating a Unit

[RussellSenior]

I have a measurment of engine emissions which has a unit of g/kw-hr.  Can I set the dimension of this to work well with quantity based calculations?  So, if I multiply it by kw-hr, I get g?  

[Brad_Turpin]

Hi Russel,

Yes, but it sounds like you need to create a couple of new units in the DIAdem unit catalog first, with unit strings that exactly match your preferred display.

Have you done that before?

Brad Turpin

DIAdem Product Support Engineer

National Instruments

[RussellSenior]

Yes, I've been adding units and new symbols.  Linear offset (from m^3 to cm^3, for example) is pretty easy.  I also kind of get the way the dimensions work, but I'm just not that comforatable with a complex unit like g/kWh.  I think the mass exponent should be 1, but I don't know how to set the dimensions for kWh.  

Follow on question, since the exponent of mass is in kg, my base unit for g/kWh needs to be kg/kWh, right? 

[Brad_Turpin · Accepted solution]

Hi Russell,

I added your "kw-hr" symbol as an alias symbol to the existing "kW h" unit, then I added an "Emission" physical quantity with a base unit of "kg/J" and an alias unit of "g/kw-hr".  I combined the "0.001" factor for kg==>g and the "3600000" factor for J==>kW h and got 2.77777777777778E-10.

Looks like it works to me.  Here's the new unit catalog I got,

Brad Turpin

DIAdem Product Support Engineer

National Instruments

[RussellSenior]

Took me a second to work out how the exponents were s^2/m^-2, but I've got it now, and it's actually quite straightforward.  This is really powerful.  Thanks for making this for me!