Converting to/from celcius

This is probably a dumb question, but here it is anyway.
I have a temerature and temperature SP i am reading from a device in celcius. I need to be able to display both in ferinheight as well as change the SP in ferinheight and then write it back to the device in celcius. unless i am missing something i can not make the conversion in the scaling due to the offset (correct?). To display the values i created an expresion tag, but am uncertain of the best/cleanest way to write the SP back in celcius.
Thanks for the help.

I believe you can use tag scaling for this. When you scale a tag you will see the scaled value and when you write to the tag Ignition will scale the value back to the PLC. If you don’t use scaling, you have to perform the calculation from the component that writes to the tag and it usually involves a little scripting.

Scaling would definately be the cleanest, but how do i handle the 32 degree offset (degC *1.8+32)? it isn’t obvious to me.

You can use scaling. The offset isn’t an issue. Set the scaling to these settings:

Scale Mode - Linear
Raw Low - 32
Raw High - 100.4
Scaled Low - 0
Scaled High - 38

This will go from Fahrenheit to Celsius.

Thanks, came to the same conclusion as soon as i hit submit on the last post.
Not sure why i was hung up on the offset. :blush: