4-23
IM 760201-01E
Measurement Conditions
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App
Index
Explanation
There are two types of input filters, line filters and frequency filters.
Selecting a Line Filter
Because the line filter is inserted into the voltage and current measurement input circuits,
it directly affects voltage, current, and power measurements (see the block diagram
in section 2.1). When the line filter is turned on, measured values do not contain high
frequency components. Thus, the voltage, current, and power of inverter waveforms,
strain waveforms, etc., can be measured with their high frequency components
eliminated.
•
You can select from one of the following cutoff frequencies.
OFF
, 500 Hz, and 5.5 kHz
• If any of the measured elements is set to a setting other than OFF, the LineFilt
indicator lights.
•
Selecting OFF disables the line filter.
• If you select 500 Hz as the cutoff frequency, the line filter is turned on automatically.
Selecting the Frequency Filter
Because the frequency filter is inserted into the frequency measurement input circuit, it
affects frequency measurements. It also affects the detection of the measurement period
for voltage, current, and power measurements (see appendix 5 for details). In this case,
the filter also acts as a filter for detecting the zero-crossing of the synchronization source
signal (see section 2.2 for details) more accurately. The frequency filter is not inserted
into the voltage and current measurement input circuits. Therefore, the measured values
include high frequency components even when the frequency filter is turned on.
•
The WT500 detects the zero-crossing point with a hysteresis of approximately 5% of
the measurement range.
•
If the line filter described above is on, it affects the frequency measurement even
when the frequency filter is off.
•
We recommend that you turn the frequency filter on when the input signal frequency is
less than or equal to 440 Hz.
•
If the frequency filters of any of the measured elements are set to ON, the FreqFilt
indicator lights.
4.8 Selecting an Input Filter
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