Appendix 5 Setting The Measurement Period - YOKOGAWA WT1800 User Manual

Appendix 5 Setting the Measurement Period

To make correct measurements on the WT1800, you must set its measurement period properly.
The WT1800 uses its frequency measurement circuit (see appendix 11) to detect the period of the
input signal that is selected using the measurement period setting. The measurement period is an
integer multiple of this detected period. The WT1800 determines the measured values by averaging
the data sampled in the measurement period. The input signal used to determine the measurement
period is called the synchronization source.
The measurement period is automatically determined inside the WT1800 when you specify the
synchronization source.
You can select the synchronization source signal from the options listed below.
U1, I1, U2, I2, U3, I3, U4, I4, U5, I5, U6, I6, Ext Clk (external clock), and None
* The available options vary depending on the installed elements.
For example, if the synchronization source for input element 1 is set to I1, an integer multiple of the
period of I1 becomes the measurement period. By averaging the sampled data in this measurement
period, the WT1800 computes the measured values for input element 1, such as U1, I1, and P1.
Deciding Whether to Use Voltage or Current Input as the
Synchronization Source
Select input signals with stable input levels and frequencies (with little distortion) as synchronization
sources. Correct measured values can only be obtained if the period of the synchronization source
signal is detected accurately. On the WT1800, display the frequency of the input signal that you have
selected as the synchronization source, and confirm that the frequency is being measured correctly.
The most suitable synchronization source is the input signal that is the most stable and that provides
accurate measured results.
For example, if a switching power supply is being measured and the voltage waveform distortion is
smaller than the current waveform distortion, set the synchronization source to the voltage signal.
Voltage
waveform
Current
waveform
App-26
Synchronization source setting:
voltage signal
IM WT1801-03EN