Logix 5000 Limit help

[Geospark]

Help file should read:

IF ([COLOR="Red"]low[/COLOR] <= high AND (value >= low AND value <= high)) OR
    ([COLOR="red"]low[/COLOR] > high AND (value <= high OR value >= low)) THEN
    light_1 := 1;
ELSE
    light_1 := 0;
END_IF;

Excellent! You've solved this puzzle.

My thoughts on what they may have accidentally done in the Help were not correct. It's just the best I could get my head around at the time to explain what we were looking at. Having revisited the LIM instruction Help in Logix Designer v30, I read this and it fits in perfectly with what you have presented...

LIM Description:

I also went to the v24 LIM instruction Help, which I had not yet done, and discovered that they had described the ST LIM equivalent correctly, earlier in the Help, but the example later in the Help has the error that was originally presented here and that you have now corrected...

There is still one small but important error in the earlier description, which I've pointed out above. The opening parentheses before the first "LowLimit" instance is missing. For clarity, the two incorrect "value" instances in the example should both be "0".

Thanks and well done!

G.

 

[AustralIan]

What?? Rockwell need to get rid of the LIM instruction and pretend it never happened.

When HighLimit = LowLimit in your new screenshot, the logic is always true.

For an instruction that you cannot be sure what it does without reading the documentation...

 

[Geospark]

A balls Rockwell. You really stuffed this one up alright!

Yes I see it now. I was concentrating on your "low" instead of "value" correction and I didn't notice they still left the "=" comparison in the second parenthesized expressions in the Help...

Should be just "greater than" like this...

IF (low <= high AND (value >= low AND value <= high)) OR
    (low [COLOR="Red"]>[/COLOR] high AND (value <= high OR value >= low)) THEN
    light_1 := 1;
ELSE
    light_1 := 0;
END_IF;

Not "greater than or equal to" like this...

Bless your eyes!

G.

 

[Geospark]

Now I'm going blind...another error I see...but who is correct?...

IF (low <= high AND (value >= low AND value <= high)) OR
    (low > high AND (value <= [COLOR="Red"]high[/COLOR] OR value >= [COLOR="Red"]low[/COLOR])) THEN
    light_1 := 1;
ELSE
    light_1 := 0;
END_IF;

...or...

Going for lunch!