Allen Bradley PLC SCP help


We have an Allen Bradley PLC programmed by others. I have two analogue
inputs connected and their inputs are programmed to a SCP Scale with
parameters block.
The two 4 to 20 mA inputs are from gas monitors ant the range of the
monitors is 0 to 90 parts per billion. Both inputs are the same and perform
the same functions.
However, both SCP blocks are scaled differently and ask if one of them is
incorrect.
4 to 20 mA input = 0 to 90 PPB.
Block 1 is programmed as
Input min = 3277
Input max = 16384
Scaled min = 0
Scaled max =90
Block 2 is programmed as
Input min = 3277
Input max = 16384
Scaled min = 0
Scaled max =900
Appreciate any advice.
TIA
Reply to
BIGEYE
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Gas monitoring isn't my field, but could it be that the system designer wanted the first sensor to give an output with a resolution of whole units but the second one with an effective resolution of 0.1 units. So he scaled the max to convert to a figure of 900 rather than 90, on the second.
Provided that the rest of the system was set up with that in mind, no problem.
ISTR one system that was actually sold as a "low resolution" system with an (expensive) upgrade to "high resolution", per channel. The upgrade came in a big box (to impress the customer that he was getting value for money) but actually consisted of a quick firmware tweak as above.
HTH Sue
Reply to
Palindr☻me
I will bet that Block 2 is a typo.. Does block 1 work correctly?
Reply to
SQLit
Yes it works correctly, I think you are right that it is a mistake.
Reply to
BIGEYE
It is easy to make mistakes when programing PLC's. I check and recheck every key stroke 3 times before walking away from a program.
Reply to
SQLit

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