ANALOG HELP

[sammy 3]

I am wondering if it is possible to use a k thermocouple, a thermo couple transmitter and a A/B 1746-NI4 set on the 4-20ma setting to give me a accurate temp reading. The thermocouple cards are out of my price range. Thanks

[Mickey 71]

Yes, you will need to scale the raw data from your card to engineering units using the "SCP" instruction or some simple math. Tell us what the 4-20ma represents ( in engineering units) and someone can give you an example.

[sammy 3]

I think the 4-20 ma represents the range of the thermocouple transmitter. 4ma would be 0 degrees and 20ma would be 600 degrees as that is the range of the transmitter. If I am wrong please guide me in the right direction. Thanks

[Mickey 71]

Most transmitters can be configured for whatever you want within the range of the thermocouple you are using. You shouldn't guess. The computer I'm on right now does not have RSLogix, but later tonite I will post an example using 0-600 degs F. If you can post your PLC program or tell us what slot to card is in that would get you a more accurate help. Edited 13 May 2011 by Mickey

[sammy 3]

Sorry, I cant post it on this pc but my analog card is the 4th slot (I4.0) the transmitter I am using is a loop type 4-20ma. Thanks

[Mickey 71]

Ok later tonight I will post an example with the info you have provided. Or someone else will jump in before that.

[sammy 3]

What I did do is: input I:4.0 3195 input min 0 input max 32767 scaled min 0 scaled max 650 output n7:0 56 I dont understand why I am getting the 56 The thermocouple transmitter is a 4-20ma 2 wire loop made by omega. (model tx52). Thanks again

[Guest]

for the current scale on a 1746-NI4 module: 4 mA = 3277 = Input Min 20 mA = 16384 = Input Max try those values for your SCP settings and see if that doesn't get you closer to where you need to be ...

[Mickey 71]

And here is a pretty picture to go along with Ron's post. You said in a previous post your transmitter was scaled 0-600 Deg, if that is not the case then change the scaled max to match your transmitters scaling. I also used a floating point destination your program may vary. An integer is ok if no decimal is required. I used F8:0 your program may already have used that register, find an unused register if necessary. Also see pdf below for data format values for your card.If you were wondering where the values Ron posted came from. DataFormat.pdf Edited 14 May 2011 by Mickey

[sammy 3]

Thanks, but how did you come up with those numbers?

[Guest]

didn't you even read the follow-up post from my distinguished colleague Mickey? ... he said: he even gave you the page right out of the analog input module's manual as an attachment ... Edited 14 May 2011 by Ron Beaufort

[sammy 3]

THIS IS WHAT I READ; And here is a pretty picture to go along with Ron's post. You said in a previous post your transmitter was scaled 0-600 Deg, if that is not the case then change the scaled max to match your transmitters scaling. I also used a floating point destination your program may vary. An integer is ok if no decimal is required. I used F8:0 your program may already have used that register, find an unused register if necessary. Also see pdf below for data format values for your card.If you were wondering where the values Ron posted came from. Attached thumbnail(s) I DID NOT HAVE TO CLICK ON THE ATTACHMENT BECAUSE HE POSTED WHAT I NEEDED. AND WHAT I ASKED IS WHERE DID HE GET THAT INFO FROM SO THAT I WOULDN'T FEEL BELITTLED BY ASKING A SIMPLE QUESTION . IF I WOULD HAVE HAD THE MANUEL THAT CAME WITH THE USED MODULE THAT I BOUGHT I WOULD NOT HAVE BOTHERED YOU. IT WAS A SIMPLE QUESTION, WASNT IT?

[Mickey 71]

Here is a link to the manual for future reference. http://literature.ro...um005_-en-p.pdf And any other AB manual you might need at link below. http://literature.rockwellautomation.com/idc/groups/public/documents/webassets/browse_category.hcst Edited 14 May 2011 by Mickey

[Guest]

Sammy ... Sammy ... Sammy ... your tone above indicates that I have offended you by what I wrote earlier ... I'm sorry for that - and I apologize that I allowed myself to be misunderstood ... I assure you that I meant no offense ... I was merely trying to make sure that you did indeed see and take advantage of the resources that Mickey had provided ... personally I don't like the way that the forum does that "frame-in-a-frame-in-a-frame" trick and I find it highly confusing ... it makes it easy to miss things in the shuffle ... and the charts that Allen-Bradley uses are often confusing to read ... a red circle here and there usually helps people understand ... but be that as it may ... I can certainly assure you that you will never be offended by anything that I will ever address to you in the future ... for some reason I feel compelled to offer you some friendly advice ... the people who contribute to these forums (myself included) do not do it for money ... we spend a lot of time and effort trying to help others understand concepts which we know (often from personal experience) can cause much confusion and frustration ... our sole repayment for our participation here is the warm fuzzy feeling that we get when someone takes the time to say "thank you that helped" ... but then occasionally we run into someone who misinterprets what weve posted and insists on taking umbrage where none was intended ... when we run into people like that we just simply ignore their posts from then on ... my friendly advice is this: in reading the forums it's best to remember that a writer can't easily convey "tone of voice" and "facial expressions" and other such clues that tend to soften the literal meaning of our specific words ... my point is that written comments (especially brief ones) that can often be interpreted as harsh and vindictive would come across quite differently in a spoken conversation ... I respectfully recommend that you make an effort to read everything addressed to you in the most generous and non-adversarial spirit possible ... in other words, don't go looking for offense where none was intended ... the truth is that it takes extra time and extra typing to be polite ... (which is what I'm doing right now) ... many of us on these forums don't have the luxury of extra time and so regretfully our posts occasionally come across as being harsher and more abrasive than we intended ... if you knew me personally then you'd realize that I am not in the habit of making snide remarks and insinuations ... simply put: insulting people is not something that I make a habit of ... once again, I regret that I expressed myself in a way that you were able to misinterpret as demeaning or belittling ... that was NOT my intention ... I will certainly not let it happen again ... please don't let my personal clumsiness affect your future enjoyment and participation in the forum ... Edited 15 May 2011 by Ron Beaufort

[mhowasso 5]

I dont mean to but in, just a comment, I didnt find what you said out of line, but Im getting a little used to the way the forum is done...but in the beginning I found myself feeling that people belittled my questions. And I think part of the reason is how the replys are posted in the frames, and not every attached graphic is readable for whatever reason, depending on what PC I use to look at them (I dont know why, it just does, maybe the network its on). No big deal, just a friendly comment.

[Guest]

this is an example of a top "Reply" button operation ...

[Guest]

and this is an example using the lower "Reply" button ... and thank you for your comment, mhowasso ...

[mhowasso 5]

Hi Ron, My learning just never stops....for 2 years Ive used this forum and never knew this..!!! :) FYI...I for one would like to say "Thank You" to you Ron, Mickey, Ken, etc., for all your help, advice on your posts/replys. Thanks, Mark Edited 15 May 2011 by mhowasso