AB analog cards

Hi, I got caught today with something I should of known but is not overly clear in the manuals.

I usually use 1762-IF4 analog input cards which are a full 16 bit resolution. I usually set them for
Scaled for PID
4 - 20 mA
which gives me an input value of 0-16383 or there abouts.
0 mA gives an input of -819 since the card uses all 16 bits including the sign bit.
The manual details that when scaled for PID is selected then the values read in are in the range 0 - 16383 ie
4 ma = 0 and
20 mA = 16383
All is good.

One this one job I had to use a 1762-IF2OF2 which is a 12 bit resolution card. Bits 0,1,2 and bit 15 are not used.
The manual reads exactly the same, scaled for PID is 0-16380 however I found that
0 mA = 0 and
20 mA = 16383
(4-20mA is the only current selection in this card)
I think it is this way since the sign bit is not used and therefore there is no way for the card to display that less than 4 mA is present if 4 mA reads 0 on the input.
I think I can see why they have done this but I wish the manual was a bit clearer about the data format as 2 near identical manuals have different meanings.

Regards Alan Case

There's nothing more that you can do on the hardware. Scaled for PID is the term used for the range native to SLC/ML PID instruction scale for PV and CV (0 to 16383 for 0 to 100%).

The solution is in program. To correct this problem, use the SCP instruction to properly scale it to your need.

I have done that. I use the SCP function, it's just taht with an IF4 and the IF2 the scaled minimum value is different (0 and 3276) for exactly the same description of the data values in the manual.
Regards Alan Case