1762-IF4 Card Problems

Good day,

I am having a problem that I cannot figure out for the life of me. I have a quality testing station that has a Compact logix PLC with a IF4 Analog Input card. I am trying to use 2 load cells where both are strain and compression load cells so I am using -10Vdc to +10Vdc @ 250Hz filtered. I have the signal running through a 3rd party signal conditioner that I have scaled to the load cell.

My problem is this....for some reason I am being asked for the most number of samples in a given window (hence the 250hz) Now I have no issue when 1 channel is enabled, but once the second channel is enabled my HMI visual scale is filtered in the fact that the card is putting out 4 exact measurements for 1 sample. The PLC runtime scan cycle doesn't change so I can see why the card is pulling data so slow. I am looking into an interrupt but I'm limited with the mediocre Compact Logix (I wish it was a control logix)

So any help would be appricated as I'm now lost. I've looked into Noise and I know that the fast update speed for the IF4 Card is to have the channels all set the same. Does Location in the Rack matter? Some sources say the back plane speed is the same even with the inter connect cable to a 2nd rack...is this True? I always though the closer the Processor the Better.

Please confirm that your module is 1762-IF4, this module belongs to micrologix family not to compact family. Can you use a weight module instead of a IF4 module ??.

Sorry Wielto,

It is a 1769-IF4 the Compact Logix / MicroLogix 1500 Card. It works for both systems. Now that I'm thinking about it, I may need a 2nd card as one load cell should really be set to 0-10Vdc as I'm only measuring in 1 direction. That way I can set up a more accurate zone and not mess with the speeds.

going deeper ...

it's hard to tell from here, but if all of the "normal" issues don't lead to anything useful, you might want to take a look at the ideas in the following two threads ... either one of these (or both) MIGHT have some effect on your system ...

http://www.plctalk.net/qanda/showthread.php?p=447080&postcount=13

http://www.plctalk.net/qanda/showthread.php?p=391975&postcount=1

can you post your entire ACD project file? ... if so, we might be able to spot something that you're overlooking ...

good luck with your project ...