Help needed with temperature measurement

[Jaco]

hi guys

I need some help with temperature measurement. I've got a NI PCI 5229 card and a powertransmitter. The power transmitter is programmed to output a 4-20mA (0°C - 100°C) signal. How can i get labview to convert this mA signal to displaying it as temperature? Please include a lot of detail as I am a first time labview user.

Thanx

[MikeS81]

Hi Jaco,
calculate gain and offset for your values. After you have this values, you can calculate your temperature. See the attached picture.

Hope it helps.
Mike

Message Edited by MikeS81 on 05-18-2008 02:44 PM

[Pnt]

The equesion is :

(Temperature)=((mA read)-4)*(100/16)

But that is true only, if the output is linear

[Jaco]

Thanx. The line isnt linear. Can I use the calibrated data and determine the line equation? How many calibrations should I do to accurately determine the equation?

[MikeS81]

Hi Jaco,
create an array with your inputs and your associated outputs. From this values you can interpolate the values you need.

Mike

Message Edited by MikeS81 on 05-18-2008 09:31 PM

[Pnt]

You probably need only a few measurments. Lets say around 6.

But that info should be available by the manufacture, also.

You can find the line equation with Excel, or Labview. I had seen a example vi, doing that. Check labview examples....