derived tags

Hi All

I have 2 derived tags files.

on my display there are 2 pairs of buttons for start and stop.

1 tag for each pair(tag1,tag2).

in one derived tag file i evaluate the push button
for the tag(tag1 and tag2) to be 0 or 1

on the second derived tag file i evaluate the expression (tag1+tag2).

the first derived tag file works fine but the second one doesn't.

why?

Thnx

Many HMI software packages support derived tags. You will probably get better answers if you identify which one you're using. Your explanation also doesn't tell much about what you want the derived tags to represent.

One thing that jumps out is that for your second derived tag, you evaluate the expression (tag1 + tag2). If your derived tag is a boolean expression, (tag1 + tag2) means (tag1 OR tag2), assuming that tag1 and tag2 are both boolean. If the derived tag is an integer, your software may not support adding two booleans.