Kobold NRM, Operating Manual

Page: 9 / 52

NRM
NRM K06/0422 page 9
7. Wiring
The instrument operates from 20 … 36 V galvanic
isolated and not grounded DC power supply in two-
wire system. (For Ex version: 20 … 30 V DC!)
The voltage value measured on the terminal of the
instrument should be minimum 20 V (in case of 4 mA)!
In case of using HART interface – to achieve proper
communication between the transmitter’s interface
and the power-supply – a minimal 250 Ohm resistance
should be maintained within the network. The
instrument should be wired with shielded cable led
through the cable gland. The wiring of the cables can
be done after removing the cover of the instrument
and the NRM-300P display unit.
IMPORTANT : The grounding screw on the housing of
the transmitter should be connected to the
equipotential network. Resistance of the EP network
should be R

2 Ohm measured from the neutral point.
Shielding of the cable should be grounded at the
control room side to the EP network. To avoid
disturbing noises, keep away of closeness to high-
voltage cables. Especially the inductive couplings of
AC harmonics can be critical (which are present at
frequency converter control) because even cable
shielding does not supply effective protection against
these cases.
2 3 4 5 6 1
1/2” NPT
Display unit
connector
Loop current
measuring connector
4...20 mA
(HART)
loop current
and supply
GND
1/2” NPT
M20x1,5 M20x1,5
3 4 2 5
U
- +
The instrument may be damaged by electrostatic discharge (ESD) via its
terminal, thus apply the precautions commonly used to avoid electrostatic
discharge e.g. by touching a properly grounded point before removing the
cover of the enclosure.
A possible electrostatic discharge can cause damage for the instrument. Do
not touch the internal terminals!