Random DC Input Fluctuation on Trend Chart

PLC: AB PLC 5/11
Module: 1771-IBD, 10- 30 VDC 16 Pt. Input
Programmable Limit Switch: Electro Cam Model PS-4011-10-P16
Software: RSLogix Build: recent.
Total Memory used 1218 words, 127 Rungs

Machine: PCMC 7050 Over Wrapper. Modified to run with the aforementioned PLC, and the DECA Controller has been replaced with the Electro Cam Programmable Limit Switch.

Problem Definition:
Random Fluctuation of the Limit Switch Input (I:000/16) on my Trend Chart. Some bizarre machine behavior.
My BK precision 40 MHz oscilloscope shows some High Frequency Noise 100 mv p-p, but I do not see the random state changes that I see on the Trend Chart. Scope Grnd is to the DC Power Supply -Out.
Any recommendations on signal conditioning?

Is the trend chart giving me bad information? Software bug? Is there some other issue I might be overlooking? I'm hoping that I am zeroing in on the problem.

Have you checked to see what is on the lead to the input, if it is lifted from the input?

I wouldn't think the 100mv would do anything as there is often more ambiant noise than that in some large facilities.

Don't know if a .01 or gimmick capacitor across lead would help, but perhaps a smaller resistor???

Just shooting in the dark here. If nothing else, this will raise the thread up in the posts, so that someone else may see it.

take the weekend off........casey

"Snubber" or in more engineering lingo a "transient spike suppressor" in a D.C. circuit a capacitor may not always be the answer we look to, but MR. X a known reactance (most people insert a cap just cause it works!). Examine the initial skew of the transient and you can roll it off third filter order with a simple PI network.
A proper C can be obtained by an implied RL, the combined reactance of the resitance of the wire and its' inherent inductance.

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