MER-MAN-14V01 (1002)
Copyright © 2014 Defi ne Instruments
12
5
WIRING
5.1 - Wiring overview
Electrical connections are made via plug in
terminal blocks at the rear of the meter. All
conductors must conform to the meter's
voltage and current ratings, and be suitably
rated for the expected temperature range to
be incurred.
When wiring the meter, check all connec-
tions by comparing the terminal numbers
shown on the meter label against the appro-
priate wiring diagrams in this manual (5.3–
5.8 and Section 6), or in the Defi ne ToolBox
soft ware.
Strip the wire, leaving around
0.25" (6mm) of bare lead exposed. If you are
using stranded wire, this should be tinned
with solder. Insert the lead into the correct
plug in the correct position, and tighten
until the wire is secure. Verify tightness by
pulling on the wire.
Follow all local codes and regulations when
wiring and installing the meter. Each ter-
minal is rated to accept one wire from #14
AWG (2.5mm) to #20 AWG. However it is
also possible to accept two #18 AWG wires,
or up to four #20 AWG wires.
5.2 - EMC installation guidelines
The Merlin has been designed to cope
with large EMC disturbances.
This has been
achieved by continual testing and improve-
ment of fi ltering and layout techniques over
many years.
The Merlin not only meets CE noise require-
ments, but surpasses them in many tests.
(For full details and test results, please see
Appendix A.)
However in some applications with less
than optimum installations and large power
switching, the EMC performance of the
Merlin can be further improved, by:
A
Installing the Merlin in an earthed metal
enclosure. This is particularly useful if
the control box is mounted close to
large power switching devices like con-
tactors. Every switching cycle there is a
possibility of generating a large amount
of near fi eld radiated noise. The metal
enclosure acting as a faraday cage will
shunt this radiation to ground and away
from the Merlin. Further improvements
can be made with this type of noise by
increasing the physical distance from
the power devices. For example, increas-
ing the control box distance from 6” to
12” from the noise source will reduce
the noise seen by the control box by a
factor of 4. Probably the cheapest and
best results in this situation could be
obtained by adding RC snubbers to the
contactors or power switches.
B
Using shielded cable on sensitive input
and control signal lines. Good results can
be obtained by grounding the shields to
the metal enclosure close to the entry
point. All cables act as aerials and pick
up unwanted R.F. radiated signals and
noise; the earthed shield acts as a fara-
day cage around the cables, shunting
the unwanted energy to ground. Shields
can also help with capacitively coupled
