Calculations

XLReporter Calculations are performed over each Interval for the Period defined in the Time Period tab.

The calculations are based on either raw or sampled values using a Connector to identify the historian, sampled values being the preferable method. For example, suppose a calculation is required from a historian that is logging every second. If raw retrieval is used then 86400 samples will retrieved for the calculation whereas if sampled retrieval (every minute) is used then this is reduced to 1440. Raw retrieval is more accurate, sampled retrieval is faster.

Before the calculations are performed, the samples are filtered using the settings on the Filter Tab.

Calculations are either raw or weighted. For raw calculations, the actual sample value is used. For weighted calculations, the derived samples value (from a stepwise curve) and the length of time is used. Typically for process values weighted is used.

For example, t0 to t1 represents an Interval and 3 values are recorded as shown.

The raw average for the Interval is 20 + 30 / 2 = 25. The time weighted average using the stepwise curve (shown in dashes) is (10 * 2 + 20 + 30) / 4 = 17.5. Note the propagation of the 10 into the interval.

When browsing for items in a group that supports calculations, the Calculations dialog appears allowing you to select one or more calculations to apply to every item selected. When a calculation is checked, the label has a number appended to it. This number indicates the order of the calculations for each selected item.

If a calculation has already been set, when browsing to change the calculation, the Replace calculation in all matching rows is available.

When this option is selected and OK is clicked, any row in the group that is set to the original calculation set when the dialog was opened is updated with the new calculation selected. For example, if the row was originally set to minimum and you re-browse, select maximum and check the Replace calculation in all matching rows option, on OK any row that was set to minimum is now set to maximum.