RTD's...how to Interpret Raw/Proportional Data?

[scootabug 0]

Hi Guys (+ Girls), I have an AB ML1200 with the 1762-IR4 RTD Module. I'm trying to interpret the Raw data value I get from the PLC as degrees celcius. I hope you can follow my logic here, feel free to ask me any questions. At present, RTD has a resistance of 104 Ohms. I get a Raw data value of -19634, so I add that to 32767 (giving me a base of 0 instead of a base of -32767) which gives me a Raw data value of 13133. So I take 13133 and divide it by 104 ohms, which gives me 126.28 per Ohm. I will use the 126.28 to calculate how many Ohms I am getting, which I can then relate to the temperature in Celcius using the 'Callendar-Van Dusen' calculation (let's not get into that right now!). For example, if I have a Raw data value of 12628...I know that I have 100 Ohms...which is 0 degrees celcius. Does that make sense to you guys? Cheers, Scoota Edited 4 Jun 2008 by scootabug

[Mickey 54]

WOW!! Where did you find all of that? If you want to have the ML1200 give you a value in deg C engineering units then instead of using raw/proportioal data format use one of the engineering formats. See pic below for different data formats. The engineering unit x 1 data format will give you a resolution of .1 deg C The engineering unit x 10 data format will give you a resolution of 1 deg C If you have a series C controller ( it supports floating point numbers) you can then divide the engineering unit x 1 format by 10 and show a decimal of one place. Also see pic below for card configuration.

[scootabug 0]

I honestly don't know if you're "takin' the piss" here or not, but thanks for the response because your engineering units pointer has now just made me realise that my hours of research and number crunching has been nothing more than a training exercise because all of a sudden it's like "BAM...the obvious answer is right in front of your face!". I'd actually looked at the Engineering Units option in the drop down list but the 3 or 4 digit number meant nothing, and all I needed to do was multiple it by 0.1. OMFG!!!!!!!!!!!!!!!! Mickey, you're a champ, I owe you a beer. This reminds me that sometimes it might be about the journey, but sometimes it's about the destination. In this case, I got both the journey and the destination! What a win Thanks again Mickey... Edited 5 Jun 2008 by scootabug

[Mickey 54]

Your Welcome. Now back to my lawn chair. Edited 5 Jun 2008 by Mickey

[evol 0]

You should be able to configure the RTD w/ the configure I/O. when you configure your RTD you should have a choice of units I believe. go to controller folder click on IO configuration and a window will pop up select the RTD from the list then click on adv config that is in the bottom of the screen on the left a new window appears click on the tab chan. 0-2 you should see in the data format it is set to raw/proportional change it to engineering units x 10 then click on generic dat extra config set the #'s to -16248 that is what i did for my project that im working on and i can read the RTD in celcius or farenheidt