Can you trust your windows?

I have seen some strange things happen with RSLogix and windows over the years, but this is a first for me.

Of course as soon as I clicked on the half true bit it cleared itself up. And, the third rung refreshed after I scrolled the screen.

I just thought I'd post this to remind us all that you can't always trust your 'puter screen.

I think your computer is preparing for a career in politics!

I've seen that behavior often on PCs with not enough memory. The lack of refresh/redraw of the screen causes alot of weird behavior.

Half green is my favorite

Can you trust your windows?

Click to expand...

obviously the answer is "no – you can NOT trust them" ...

one of the hardest parts of teaching PLC troubleshooting skills to maintenance technicians is prying their noses off of the computer screen ...

my personal favorite "issue" is the one where a technician in the control room manually toggles an output bit to a ONE status – and then watches it stay a ONE for several seconds before it automatically changes back to a ZERO ... meanwhile his buddy is on the walkie-talkie watching the relay cabinet to see which relay pulls in ...

(of course, behind the scenes, the PLC processor is actually turning the bit back to a ZERO within one scan period – but the screen display takes a second or two to update and show the ZERO in the bit) ...

the dialog on the walkie-talkie usually goes something like this:

"OK, here we go – it's ON - it's ON - it's ON - it's ON – now it's back OFF again" ...

"I didn't see nothing" ...

"Get ready and let's try it again, watch careful this time ... OK – it's ON - it's ON - it's ON - it's ON – now it's back OFF again" ...

"I STILL didn't see nothing" ...

this is a case where a guy has enough knowledge to know that "a ONE in the bit means the output is ON in the field" – but he doesn't realize that the ONE status he sees on the screen for two or three seconds isn't really accurate because of "update" issues with the screen display ...

only after the students have witnessed NUMEROUS examples of how the screen display can lie, then (and only then) will they start paying attention to the little "tricks of the trade" that can go FAR BEYOND what the screen is able to show ...

I've also seen the half-green bit occur over a slow connection such as remote dial-up.

This can also happen if you have comms issues. The spinny thing with the paddles gets pig slow too. The worst case I've seen was when some idiots wired up the DH+ in a star configuration, and no terminators, of course. Took the better part of an hour to up/download a middling sized application.