4.4 Viewing Harmonic Measurement Values
67
4
Chapter 4 Viewing Measurement Values
The [Harm sync src] has to be selected for harmonic analysis. Available selections depend on the input
source.
• Using a measurement voltage or current input as the sync source
The frequency of the measurement voltage or current waveform is sampled for harmonic analysis syn-
chronization.
For all channels, the (0
°) reference point for all phase angle measurements is the fundamental wave-
form of the harmonic sync source.
• Using the instrument's internal fixed clock as the sync source
Waveforms are sampled in synchronization with the 50 ms timing used by the instrument for data
update and for harmonic analysis. Use this source when no input is stable enough for synchronization.
When DC100 ms is selected, 50 Hz is measured as the fifth-order harmonic, and 60 Hz as the sixth-
order harmonic.
•
Using an external signal as the sync source
This setting is available only when a Model 9791 Motor Testing Option or 9793 Motor Testing and D/A
Output Option is installed and CH B is set for pulse input. Waveforms are sampled in synchronization
with the rising edges of the pulses input on CH B to perform harmonic analysis.
See"4.8.1 Motor Input Settings" (p. 84)
4.4.4 Selecting the Harmonic Sync Source
U1 to U4, I1 to I4
DC50 ms, DC100 ms
Ext
Display the
[Input] page
Select with the F keys
See About [Next].
"2.2 Basic Operations" (p. 16)
Select the item
• The same harmonic sync source is shared by all channels. Harmonic analysis cannot be per-
formed correctly on channels with input frequency different from the selected harmonic sync
source.
• The harmonic sync source selected here is also used as the sync source for waveform dis-
plays.
• Correct analysis is not possible in the following situations:
1. If the sync source signal is very distorted
2. If the sync source signal frequency is below the lower limit of the valid range
3. If the sync source frequency is unstable
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