I'm a idiot how to scale!!

jasil · Jan 14, 2015

I'm confused SLC500 is fine I understand, but Controllogix 5000 revision 20.

1756 IFHI8 card how do I scale the input? The input is a dumb analog device 4-20ma and I can obviously change the high engineering and low engineering units, but where can I see the raw data?

The transducer isn't ever outputting a true 4ma my guess would be 8ma with a high range of maybe 15ma. Where can I see the raw data to scale it accordingly?

jasil · Jan 14, 2015

I've got that lol............how do I know the real MA input to the card though? That's just the range why can't I actually see the MA range in realtime, so I can scale accordingly.

I could put the engineering units at whatever I want, but the transducer will never hit the 4ma nor will it ever hit 20ma, so the scaled input range might be 7.65ma min and 17.37 max?

Make sense or no? How can I look at the card and get those min and max levels by moving a field device?

rootboy · Jan 14, 2015

A VOM connected in series set to the milliamp scale comes to mind...

jasil · Jan 14, 2015

rootboy said:
A VOM connected in series set to the milliamp scale comes to mind...

I agree I was hoping in this age and seeing that it is Controllogix it would show the raw input data. If a SLC shows it why doesn't the array of HART cards now used by AB?

Yes, that is the last resort.

robo77 · Jan 14, 2015

have you looked at the local input tags?

jasil · Jan 14, 2015

robo77 said:
have you looked at the local input tags?

You just made the light bulb come on. Couldn't I just put the High and Low engineering units at 4ma and 20ma and see what the channel data is at that point? That would give me a accurate reading, at least I think it would.

robo77 · Jan 14, 2015

normally I do put the high and low units at 4 and 20.. send a signal and figure the scale. not figure but setup the scaling.

jasil · Jan 14, 2015

Thx for making the lightbulb come on

robo77 · Jan 14, 2015

set input rang 0-20 ma. high signal 20 low 0. high eng 2000 low 0. then I get a raw value in ma.

robo77 · Jan 14, 2015

I am sure there are other ways .. just more what I am used to for raw numbers.

widelto · Jan 15, 2015

See attached file.

A picture is worth than 1000 words.
You can use 4000 and 20000 for raw engineering instead of enegineering units.
Then you can use 4000-20000 range as your input for a block scale or AOI instruction.

electric06 · Jan 15, 2015

Here is another way to do the scaling so that you can see the raw counts and the ma readings. You set your analog card's comm format to integer data then using the function block programming scale the raw data for your deivce, it seem to work well.

jseavers · Jan 15, 2015

I Scale all my analog inputs to what I would read with a meter for a troubleshooting then scale into user units for the program.

Sherlock4me · Jan 15, 2015

https://www.youtube.com/watch?v=yWe244o4uwk

rootboy · Jan 15, 2015

jasil said:
I agree I was hoping in this age and seeing that it is Controllogix it would show the raw input data. If a SLC shows it why doesn't the array of HART cards now used by AB?

Yes, that is the last resort.

Last resort? If you aren't sure about what your transmitter is putting out compared to what the PLC is reading, this would be my first stop.

The CLX will show the raw data, at the most you have to create a tag and load it in.

We scale ours here to 30840 (upper end obviously) to give us some head room in case there is a transmitter failure (which then would pump out 22 ma). So anything substantially above 30840 would indicate that there was a problem with the transmitter.

Maybe I didn't fully understand the question.

And what's this about HART?

I'm a idiot how to scale!!

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