1771 IFE/C Analog for plc 5

I have a tonnage monitor module hooked up to an analog card using a plc 5-30.
Analog Card is a 1771 IFE/C. We had the OEM visit to do calibration on the tonnage module, And found that we cannot display anything in the 700 range.
for example while tweaking the calibration pods slightly after getting a reading in the high 600 range tonnage display would jump to a value in the 800's. No matter what we did we couldnt get readings in the 700 range. The display is done via block transfer and displayed on a pv 1000e. The tech said there isnt an issue with the tonnage module as it dispalyed 700's with the unit he was using to calibrate with. just wont show 700 range when going through my analog card.
I am not an expert on these cards, So I was wondering if anyone here might have an idea as to why I might be having this issue. Must be the ife/c card but not sure why. Thanks in advance for any information

Have you monitored the actual input ( voltage or current) to see if it is jumping?

Can you remove the input from the tonnage module and input a variable test signal to the analog card?

if you have the entire PLC program file (RSP extension) post it as an attachment and we'll be glad to take a look ...

ASSUMING (gosh I hate that word) that everything "electrical" - and in the signal configuration is OK, then here is a GUESS as to what might be happening ...

suppose that the scaling for your system is non-linear ... in cases like that, the programmer will often program the scaling conversion factors in "steps" ... for example:

if the input signal is between 4 to 5 milliamps - then multiply by 1.2 ...
if the input signal is between 5 to 6 milliamps - then multiply by 3.4 ...
if the input signal is between 6 to 7 milliamps - then multiply by 5.6 ...
etc. ...

(naturally these numbers are just examples for discussion) ...

so ...

sometimes the programmer "drops a stitch" while entering the conversions, which might indeed make your system act the way you have described ...

once again, post your program code here and we'll take a look ... you'll have to zip the file first (forum rule) ...

and welcome to the forum ...

Thanks for the suggestions Mickey and Ron,
I only had a short window to get the calibration done before production had to resume so I didn't get to check with a variable test signal to the analog card. I will at the next opportunity. Looking through the logic I dont see any scaling going on for the analog card.
The logic is pretty simple just a rung with XIC which enables a MOV of N12:11 to O:061 and continues 3 more times with N12:12 to O:062 N12:13 to O:063 and N12:14 to O:064. Looking at the PV program to display the tonnage number the address for the left front corner is address O:061/00-1/17 Data Source is Remote IO and Data Type is Binary. Could this be an issue? when I have a look at the data table for O:061 there is no O:061/8 or O:061/9 Could this be where I am losing my 700 range? Thanks for the help guys.

the analog signals from your 1771-IFE/C module do not have addresses that begin with the letter "I" ... instead the signals will be brought into an INTEGER file - which begins with the letter "N" ... we won't know exactly WHERE in the integer file (or even WHICH integer file) until we track down the Block Transfer Read instruction associated with your IFE module ...

N12:11 through N12:14 certainly COULD be the addresses of your analog inputs - but we can't tell for sure based on what you've posted so far ...

Looking through the logic I dont see any scaling going on for the analog card.

Click to expand...

the scaling COULD be going on inside the IFE card itself ... the module's Configuration Data would tell us whether or not that's actually being done - and whether or not it's being done correctly ...

when I have a look at the data table for O:061 there is no O:061/8 or O:061/9 Could this be where I am losing my 700 range?

Click to expand...

the digital I/O addresses for your PLC-5 system use the OCTAL numbering system ... that's why you don't see the bit addresses "/8" and "/9" on your I/O data tables ...

it's possible that the original programmer wasn't aware of this OCTAL numbering - especially if he was more familiar with the DECIMAL numbering system used for the Allen-Bradley SLC/MicroLogix platform ... (those systems DO have the "/8" and "/9" bit numbers) ... we'd need a lot more detail in order to know whether or not that's a part of your problem ...

you REALLY need to post the ENTIRE program file (RSP extension) if you want any detailed help with this ... otherwise, we're just guessing ...

good luck with your project ....