App-33
IM 760301-01E
App
Appendix
Appendix 7 Data Update Rate and Computing
Equation
AC signals fluctuate repetitively when viewed instantaneously. The power of AC signals
can be measured by taking the average of the repeating periods or computing the
average by filtering the data of several periods. The WT3000 automatically selects the
computing method from the two averaging computations above according to the data
update interval.
• 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 detects the period of the input signal assigned to be the synchronous
source
*
using the frequency measurement circuit and sets the measurement period to
be an integer multiple of the input signal period. Computation including simple
average is performed based on the sampled data in this measurement period. This
method requires that the period of the assigned synchronous source signal be
detected accurately. The synchronization source must be set when using this method.
The period of the assigned synchronization source signal must also 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.
The EAMP method sets the measurement period to be the entire data update interval.
Computation including exponential average is performed by applying digital filtering on
the sampled data in this measurement period. This method does not require the input
signal period to be detected accurately. Therefore, you do not have to set the
synchronization source.
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