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4.2 Selecting the Measurement Synchronization Source
Explanation
4-4
Function used to select the measurement synchronization source
The instrument determines the measured value by averaging the sampled data
(averaging process) over the period synchronized to the input signal period. The input
signal period is detected from the voltage and current signals and you can select which
signal period to use to perform the averaging process. The initial setting is A.
• A
Priority is placed in detecting the current signal period to be used as the synchronization
source. The current signal of each element is used as the synchronization source for
the respective elements. If the period of the current signal cannot be detected, the
voltage signal is made the synchronization source.
• V
Priority is placed in detecting the voltage signal period to be used as the synchronization
source. The voltage signal of each element is used as the synchronization source for
the respective elements. If the period of the voltage signal cannot be detected, the
current signal is made the synchronization source.
• oFF
Measurement is not made by synchronizing to the voltage or current signal, but the
sampled data over the entire period of the display update rate is averaged.
Note
•
Select an input signal with stable input level and frequency (with little distortion) for the
synchronization source. As a guideline, select a signal whose frequency can be stably
measured.
For example if the object under test is a switching power supply and the distortion in the
voltage waveform is less than that of the current waveform, set the synchronization source
to V.
Voltage waveform
Current waveform
For example if the object under test is an inverter and the distortion in the current
waveform is less than that of the voltage waveform, set the synchronization source to A.
Voltage waveform
Current waveform
•
Zero cross is the timing at which the synchronization source crosses over (when rising
or falling) the level zero (center value of the amplitude). Because it may be impossible
to stabilize and calculate the zero cross if the synchronization source waveform is
distorted and superimposed with harmonics and noise, the measured voltage and
current values may be unstable. In this case, change the settings for the
synchronization source, and turn ON the frequency filter. See section 4.3, for
information on the frequency filter. As in the inverter example above, turn ON the
frequency filter even if high frequency components were superimposed.
•
When measuring DC signals, the measurement interval may be erroneous if noise
crosses level zero and is recognized erroneously as a zero cross by the true signal. To
avoid this, turn OFF the synchronization source. By turning the synchronization source
OFF, sampling data from all intervals of the display update rate are used to calculate
the measured values.
•
If the period of the voltage or current signal cannot be detected even when "A" or "V" is
selected, the sampled data over the entire period of the display update rate is averaged.
IM 760401-01E
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