YOKOGAWA WT210 User Manual page 76

4.4 Selecting the Measurement Range When Using Direct Input
Explanation
4-8
To ensure safe operation, if the current to be measured exceeds 7 A (rms
value), use a cable or conductor that is capable of running a current higher than
the current to be measured, and be sure to connect the protective earth before
operating the instrument. The protective earth terminal is provided on the rear
panel of products shipped in January 2004 and later.
Fixed Range (manual) versus Automatic Range (auto)
The measurement range can be of one of the following types. The initial setting is
Auto range ON.
• Fixed range
Select the voltage range from the following:
• When the crest factor is set 3: 600, 300, 150, 60, 30, or 15 V
• When the crest factor is set 6: 300, 150, 75, 30, 15V, or 7.5 V
Select the current range from the following:
• When the crest factor is set to 3: 20, 10, 5, 2, 1, or 0.5 A (200 mA, 100 mA, 50
mA, 20 mA, 10 mA, and 5 mA are also selectable on the WT210)
• When the crest factor is set to 6: 10, 5, 2.5, 1, 0.5, or 0.25 A (100 mA, 50 mA,
25 mA, 10 mA, 5 mA, and 2.5 mA are also selectable on the WT210)
• Auto range: Auto
The measuring range is adjusted automatically according to the input voltage or current
as follows. Overrange is handled the same way as for the manually selected range.
• Range up:
When the measured value of voltage or current (V or A) exceeds 130% of the
rated range or when the peak value (instantaneous voltage or current value that
is sampled) exceeds approximately 300% of the rated range, the range is
increased the next time the measured value is updated. On the WT230, when
any of the input elements meets the above condition, the range is increased the
next time the measured value is updated.
• Range down:
When the measured value of the voltage or current is less than or equal to 30% of
the rated range and the peak value is less than or equal to approximately 300% of
the rated range of the next lower range, the range is decreased the next time the
measured value is updated. On the WT230, when all of the input elements meet the
above condition, the range is decreased the next time the measured value is updated.
Verifying the Range
To verify the current range setting press the VOLTAGE key or the CURRENT key.
The result will be shown at display C. In order to return to the measurement status,
press the same key again.
Note
When the range is set to auto, the range may be adjusted frequently if a waveform such as a
pulse is input. In such a case, set the range manually.
Power Range
The measuring range for active power, apparent power and reactive power is
determined as follows.
Wiring method
single-phase, two-wire (1P2W)
single-phase, three-wire (1P3W)
three-phase, three-wire (3P3W)
three-voltage, three-current (3A3V)
three-phase, four-wire (3P4W)
WARNING
Power range
voltage range × current range
voltage range × current range × 2
voltage range × current range × 3
IM 760401-01E