Hioki 8841 - Page 51

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2.10 Notes on Measurement
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CAUTION
Before using the unit, make sure that the sheathing on the input cables
is not damaged and that no bare wire is exposed. If there is damage,
using the unit could cause electric shock. Replace with the specified
9197 or 9198 CONNECTION CORD.
When making measurements on an AC power line for example, using a
voltage transformer, be sure to connect the voltage transformer ground
terminal to ground.
NOTE
AC DC DC+AC
0V
+400 VDC
-400 VDC
･ Strong wind striking the input terminal can disrupt the thermal balance of
the input circuit, resulting in incorrect readings. When taking
measurements in windy environments, arrange the equipment to prevent
wind from directly striking the input terminal of the 8937.
･ Abrupt changes on ambient temperature can also disrupt the thermal
balance of the input circuit. To prevent measurement error, allow the unit
to adjust to the new temperature for about one hour before starting
measurement.
Difference between "370 VAC/DC" and "400 VDC max." indication
370 VAC/DC: RMS value is displayed.
400 VDC max.: Instantaneous value is displayed.
The maximum input voltage (400 VDC max.) is defined as the superposition
of DC component and AC peak, as shown in the figure below.