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7.5 Selecting the PLL Source
7-24
French
L'application d'une tension comprise en dehors de la plage 0 à 5V sur le connecteur
d'entrée d'horloge externe (EXT CLK) risque de provoquer un endommagement de
l'instrument.
Note
•
Select a signal that has the same period as the target signal for the harmonic
measurement. Selecting an input signal with little distortion for the PLL source enables
stable harmonic measurement. If the fundamental frequency of the PLL source fluctuates
or if the fundamental frequency cannot be measured due to waveform distortion, correct
measurement results will not be obtained. If the distortion of the voltage signal is smaller
than that of the current signal such as when the measured item is a switching power supply,
it is recommended that the PLL source be set to the voltage.
If all the input signals are distorted or the amplitude level is small with respect to the
measurement range, the specifications may not be met. To achieve accurate measurements
on the high orders of the harmonics, set the PLL source to external clock and apply a signal
with the same period as the input signal to the external clock input connector.
•
If the fundamental frequency is less than or equal to 440 Hz and the signal contains high
frequency components, it is recommended that the frequency filter be turned ON. This filter
is effective only on the frequency measurement circuit.
•
If the amplitude level of the signal input to the element specified as the PLL source is small
with respect to the range, PLL synchronization may not be achieved. If the crest factor is
set to 3, set the measurement range so that the amplitude level of the PLL source is at least
50%. If the crest factor is set to 6, set the measurement range so that the amplitude level of
the PLL source is at least 100%.
•
If the frequency of the PLL source changes, correct measured values are displayed from the
th
4
data update after the change. Correct measured values may not be obtained immediately
after the frequency of the PLL source changes or after changing the PLL source, because
the PLL circuit inside this instrument redetects the frequency.
•
If you set the PLL source to Smp Clk in wide bandwidth harmonic measurement mode and
change the measurement mode to normal measurement, the PLL source is set to Ext Clk.
ATTENTION
IM WT3001E-51EN
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