Hioki 3511-50, Instruction Manual, Page: 71 / 140

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5.6 External Interference
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5.6.1 Countermeasures Against Interference from the Power
Supply Line
5.6 External Interference
The 3511-50 is designed to be resistant to errors caused by interference from
the test cables or the power supply line. However, if the level of the
interference is particularly large, this can cause measurement errors or faulty
operation.
Refer to the examples given below for examples of countermeasures which
can be taken against interference which has caused faulty operation etc.
If noise is present in the power supply line, its influence can be moderated
by the following countermeasures:
(1) Grounding by using a protective ground wire
The 3511-50 unit is constructed so as to be provided with protective
grounding via the ground lead in the power cord.
This protective grounding serves the important function, not only of avoiding
the possibility of electric shock to the operator, but also of eliminating noise
from the power supply line by the provision of an internal filter.
Be sure to connect the 3511-50 unit to a properly 3-wire power supply
socket, using the grounded power cord which is supplied with the unit.
(2) Inserting a noise filter in the power supply line
Any excessive noise present in the power supply line can be suppressed by
purchasing a socket type noise filter (generally available commercially)
which can be inserted into the power supply socket, with the 3511-50 unit
connected to the output of the noise filter.
Various types of such socket type noise filters are readily available from
specialist manufacturers.