2-14
IM 760301-01E
Data Update Interval «For the procedure, see section 4.10.»
• Limitation on the Data Update Rate by Measurement Modes
• Normal Measurement Mode, Waveform Computation Mode, and FFT Mode
The data update rate setting is valid. However, the display update interval in waveform
computation mode and FFT mode is the data update rate + computation time.
• Wide Bandwidth Harmonic Measurement Mode and IEC Harmonic
Measurement Mode
The data update rate setting is invalid. The data update rate is automatically
determined by the fundamental frequency and the number of periods of the PLL source.
• Voltage Fluctuation and Flicker Measurement Mode
The data update rate is fixed to 2 s.
• Cycle-by-Cycle Measurement Mode
The data update rate setting is invalid. The data update rate is automatically
determined by the fundamental frequency and the number of measurement cycles
of the synchronization source.
• Data Update Rate in Normal Measurement Mode, Waveform Computation Mode,
and FFT Mode
You can select the value from 50 ms, 100 ms, 250 ms, 500 ms, 1 s, 2 s, 5 s, 10 s, and
20 s. The numeric data is updated at the selected interval. To capture relatively fast
load fluctuations in the power system, select a fast data update rate. To capture
relatively low frequency signals, select a slow data update rate.
The WT3000 automatically selects the computing method from the two averaging
computations below according to the data update rate. For details, see appendix 7.
• When the Data Update Rate Is 50 ms, 100 ms, 5 s, 10 s, or 20 s
Computation is performed using ASSP (Average for the Synchronous Source
Period) on the sampled data within the data update interval to calculate the
measured value. (However, integrated power WP as well as integrated current q
during DC mode are excluded.)
This method requires the period of the assigned synchronous source signal to be
detected accurately.
Check to see that the frequency of the synchronous source signal is being
measured correctly according to the procedures given in sections 5.1 and 5.3.
*
For a description of the synchronous source, see appendix 6, “Setting the Measurement Period.”
• When the Data Update Rate Is 250 ms, 500 ms, 1 s, or 2 s
Computation is performed using EAMP (Exponential Average for Measuring
Period) on the sampled data within the data update interval to calculate the
measured value. This method does not require the input signal period to be
detected accurately.
Hold «For procedures, see section 4.11.»
The data display of each measurement function can be held. The communication output
data while the display is held is the held numeric data.
Single Measurement «For procedures, see section 4.11.»
While in the hold condition, a measurement is performed once at the specified data
update rate and enters the hold condition.
2.3 Measurement Conditions