Analog Signals

Using RSLogix 5000 version 20.05 with a 1769-IF8 analog card set to 4ma-20ms which is set to engineering units with a 10hz filter. I am wondering if the is a way to grab a min/max value from the signal coming in?

I would compare the input with GRT and LES to some variable if it's bigger/ smaller then the previous, overwrite that variable with MOV

Simple way, I think, is what I have used before.
Others may have better ways...

Signal is X
Max is A
Min is B

If X > A, then Mov X to A
If X < B, then Mov X to B

Then A (max) and B (min) are always getting updated.

Lary said:

Using RSLogix 5000 version 20.05 with a 1769-IF8 analog card set to 4ma-20ms which is set to engineering units with a 10hz filter. I am wondering if the is a way to grab a min/max value from the signal coming in?

Click to expand...

I think the OP is asking for the extrema of the raw values i.e. before the 10Hz, low-pass filter.


I think one way would be to wire* the same signal to a free channel and put a 500Hz filter on it.


Another way would be to change the 10Hz filter setting to 500Hz and do the 10Hz filtering in the PLC, along with the extrema montoring. I imagine this could be done in an AOI.



* I have no idea how to wire this; it's current, so to my simple mind putting them in parallel should work; you may ROFL at me now.

drbitboy said:

* I have no idea how to wire this; it's current, so to my simple mind putting them in parallel should work; you may ROFL at me now.

Click to expand...

If that's what the OP wants it's series connection. Parallel would split the current. Of course the transmitter would have to support the extra load when in series.

I think we need to have the OP clarify what he means by "the signal coming in" if you are right.