Graphic Function Components
PI DataLink User Guide
Specify where you want to place the resulting function array using the Output Cell field. If
you select a cell before the function dialog or task pane is displayed, the currently-selected
cell is used as the default Output Cell value.
The output cell value always specifies the top left corner of the function array. If you append
(page 16) timestamps and other data, keep in mind that the data column may be shifted
downward or to the right of the output cell location, overwriting data in those adjacent cells.
If you click in the Output Cell field and then select a multi-cell array in the spreadsheet, you
can override the default display of all function results. Instead, only the results that fit within
the specified array dimensions are displayed.
Many PI DataLink functions require Start Time and End Time arguments to retrieve an
array of event values over a specific time range. Follow these guidelines when specifying
Time strings may be entered directly in edit fields in either absolute or relative PI time
(page 71) formats (for example, 10-Dec-99 19:12 or -3h).
If the start time is more recent than the end time, results are displayed in reverse
Timestamps referenced in spreadsheet cells may also use fixed or relative PI time
formats, and should be preceded by an apostrophe to indicate a string (for example,
'10-Dec-99 19:12 or '-3h).
Cell references may also use the absolute Excel time format (such as 39299.6146,
equivalent to 8/5/2007 2:45:00 PM). Excel stores timestamps in this format, which
represents the cumulative number of days since 1900. Excel can display the same
timestamps using any date-time format assigned to the cell.
Some arguments call for an interval or duration of time, represented by a single value
rather than start and end times. Whether referenced or entered directly, interval values
should use relative PI time strings such as a number followed by a time variable (for
example, 1d or 30m), and may not specify or refer to a fixed PI or Excel timestamp. For
example, to specify an interval of 32 minutes, enter or reference a cell containing the
To enter intervals in terms of frequency, convert the frequency to equivalent seconds. For
example, a frequency of 25 Hz should be entered as a 0.04s interval (=1/25 of a
When using relative formats (for example, -2h), the reference time used to translate the
time format is different for function start and end times. The current wall clock time is
the reference for a relative start time, but the start time is then used as the reference for a
relative end time.
Note: PI DataLink supports only the default 1900 date system supported by Excel. PI
DataLink does not support Excel's 1904 date system, and returns incorrect time
stamps if this system is used.