How to make a rounding operation with an Arithmetic Module?



The arithmetic module only includes CEIL or FLOOR operations, no ROUND operation.
We can create one using an IF statement.

Let's say we want to round S1 to the closest integer. The function is:


How does it work?
Example: S1 = 12.7. The expected result for rounding is 13.

(CEIL(S1)+FLOOR(S1))/2 = 12.5

A test is done: if S1 is lower than (CEIL(S1)+FLOOR(S1))/2, it will return FLOOR(S1). If not, it returns CEIL(S1).
In the example, the test "12.7 < 12.5" is false, so the function returns CEIL(12.7)=13.

What happens in the 12.5 case?
The function is still correct. "<" means "strictly lower than".
So the test "12.5 < 12.5" is technically False, the function returns CEIL(12.5)=13, which is the expected result.

More information:
IF(S1<(CEIL(S1)+FLOOR(S1))/2,FLOOR(S1),CEIL(S1)) contains exactly 48 characters, which is the limit for the arithmetic module in the meters (limit is 249 in the VIP).
So rounding the S1-S8 inputs is OK, but rounding (S1+S2) or S1/1000 requires an additional arithmetic module.
Check the ION Reference for more details.

Last Revised: November 13, 2007
All content © 1992-2007 Schneider Electric

Legacy KB System (APS) Data: RESL189173 V1.0, Originally authored by KBAdPM on 11/14/2007, Last Edited by KBAdPM on 11/14/2007
Related ranges: ION Programming