2-18
IM WT1801-01EN
Measurement Period (SYNC SOURCE)
Measurement Period for Measurement Functions Used in Normal Measurement
The measurement period is determined by the input signal that is used as the reference (synchronization
source). The measurement period is set within the data update interval between the first point where the sync
source crosses the level-zero point (center of the amplitude) on a rising slope (or falling slope) and the last point
where the sync source crosses the level-zero point (center of the amplitude) on a rising slope (or falling slope).
Data update interval
Measurement period
Synchronization source
Rising zero crossing
Falling zero crossing
If there is not more than one rising or falling slope within the data update interval, the entire data update interval
is set as the measurement period.
Data update interval
Measurement period
Synchronization source
The measurement period for determining the numeric data of the peak voltage or peak current is always the
entire span of the data update interval. Therefore, the measurement period for the measurement functions that
are determined on the basis of the maximum voltage or current value (U+pk, U-pk, I+pk, I-pk, CfU, and CfI) is
also the entire span of the data update interval.
For details, see appendix 5 in the getting started guide, IM WT1801-03EN.
Measurement Period for Measurement Functions Used in Harmonic Measurement
The measurement period extends from the first sample in the data update interval for the number of points
indicated below:
• When the data update interval is 50 ms, 100 ms, or 200 ms: 1024 points
• When the data update interval is 500 ms, 1 s, 2 s, 5 s, 10 s, or 20 s: 8192 points
The WT1800 determines the harmonic sampling frequency automatically based on the period of the signal
that is set as the PLL source. The sampling data and measurement period that are used to determine the
values of harmonic measurement functions may be different from those used to determine the values of normal
measurement functions.
Element1 to Element6
Use the soft keys to select an element, and then select the signal to use as the sync source from the options
listed below. The available options vary depending on the installed elements. When independent input element
configuration is off, elements in the same wiring unit have the same sync source.
U1, I1, U2, I2, U3, I3, U4, I4, U5, I5, U6, I6, Ext Clk (external clock),
*
and None
* When you select Ext Clk, the external signal applied to the external clock input connector (EXT CLK) on
the rear panel is used as the sync source. For the EXT CLK connector specifications, see section 4.3 in the
getting started guide, IM WT1801-03EN.
2 Fundamental Measurement Conditions