NCR-80 Four-wire 4-20 mA/HART
925-0332 Rev B
5 Connecting to power supply and bus system
29
NPT thread
In the case of instrument housings with self-sealing NPT threads, it is not possible to have the
cable entries screwed in at the factory. The free openings for the cable glands are therefore cov-
ered with red dust protection caps as transport protection.
Prior to setup you have to replace these protective caps with approved cable glands or close the
openings with suitable blind plugs.
With plastic housing, the NPT cable gland or the Conduit steel tube must be screwed without
grease into the threaded insert.
Max. torque for all housings, see chapter "
Technical data
".
If screened cable is required, we recommend connecting the cable screen on both ends to
ground potential. In the sensor, the screen should be connected directly to the internal ground
terminal. The ground terminal on the outside of the housing must be connected to the ground
potential (with low impedance).
In Ex systems, the grounding is carried out according to the installation regulations.
In electroplating and CCP systems (cathodic corrosion protection) it must be taken into account
that significant potential differences exist. This can lead to unacceptably high currents in the ca
-
ble screen if it is grounded at both ends.
Information:
The metallic parts of the instrument (process fitting, sensor, concentric tube, etc.) are connected
with the internal and external ground terminal on the housing. This connection exists either
directly via the conductive metallic parts or, in case of instruments with external electronics, via
the screen of the special connection cable.
You can find specifications on the potential connections inside the instrument in chapter "
Techni-
cal data
".
5.2 Connection
The voltage supply and signal output are connected via the spring loaded terminals in the hous-
ing.
Connection to the display and adjustment module or to the interface adapter is carried out via
contact pins in the housing.
Information:
The terminal block is pluggable and can be removed from the electronics. To do this, lift the
terminal block with a small screwdriver and pull it out. When reinserting the terminal block, you
should hear it snap in.
Proceed as follows:
1. Unscrew the housing lid
2. Loosen compression nut of the cable gland and remove blind plug
3. Remove approx. 10 cm (4 in) of the cable mantle (signal output), strip approx. 1 cm (0.4 in)
insulation from the ends of the individual wires
4. Insert the cable into the sensor through the cable entry
