How do I compare two variables in mapping on the HI 3000 or 4000 series units?

How do I compare two variables in mapping? I want to compare two values in my Hardy 3000 and/or 4000 series unit and then set a relay if one is greater than the other one.

Using the Hardy HI 3000 or HI 4000 series units (which includes the HI 3010, HI 3030, HI 3300, HI 3600, HI 4050 and the HI 4060), the way to do a comparison like you are describing would be to use a analog destination and your two values to compare as the source.

Example: "C = B + ~A", where value "A" is a set value and you want to know when value "B" exceeds value "A". The source side of the equation would be "B +~A". So as "B" increases, it is subtracting the value of "A" every scan. As long as value "B" is less than "A", then the destination value "C" would be less than zero. Once "B" is greater than "A", then the destination value would be set to greater than zero.

With this equation present, you would then do another map equation where you would have a Boolean bit or trigger bit being equal to the value "C" in the first equation. So "D = C" would be the map where "D" is the trigger for your relay (or may be your relay in mapping). Once "C" became a value above zero in the first equation, then it would set "D" high in the second equation. Your relay would energize.

You could use one of the local relays as the destination "D" directly or use the Boolean bit "D" as a trigger for your relay.