"RTD Voltage to temperature conversion" for temperatures below 0 degrees

[ES-Iris]

NI gives us a conversion VI for temperatures above 0 degrees Celsius. I need a converter also for negative temperatures.
Where can I find such a VI or a method ?

[Filipe A.]

Hello;

One thing you can do is, instead of using a VI, to convert the temperatre of the RTD to a negative value by using the Measurement and Automation Explorer.

By using the Scale in MAX, you can insert an offset to drag the values down to negative values.

Hope this helps.
Filipe A.
Applications Engineer
National Instruments

[Labviewguru]

Filipe,

Gosh, I was interested in this one, and kinda curious myself why you couldn't convert temperatures below 0degC. I looked up RTDs in the Omega Catalog, and sure enough, they go to at least -200degC.

Would National Instruments be interested in a new algorithm that is capable of converting all temperatures? If so, I'll do the legwork, find the correct algorithm, and program it up.

[DougD]

Labviewguru and Filipe:

I found the following rather excellent reference on line as a PDF by
searching RTD+NIST+equation at:

http://www.data-acq.co.uk/pdf/CHAP-4.pdf

It has the NIST polynomial equations and technical descriptions for
various types of thermocouples and RTDs. I think it is just what you
are looking for.
You'll just have to slap them into a LabVIEW equation box and that
should be that.

Douglas De Clue
ddeclue@bellsouth.net



Labviewguru wrote in message news:<50650000000500000021880000-1023576873000@exchange.ni.com>...
> Filipe,
>
> Gosh, I was interested in this one, and kinda curious myself why you
> couldn't convert temperatures below 0degC. I looked up RTDs in the
> Omega Catalog, and sure enough, they
go to at least -200degC.
>
> Would National Instruments be interested in a new algorithm that is
> capable of converting all temperatures? If so, I'll do the legwork,
> find the correct algorithm, and program it up.