Chapter 5 Installing the system

Page 5.6

5.8 Step 5: Making the external connections
1. Refer to the documentation supplied with the external equipment to see if you have to carry out any special
procedures when connecting them to the 7951. Take special notice of any information about safety
requirements in hazardous areas, and complying with EMC regulations.
2. For each D-type connector, pass the connector hood over the cable and wire up the connector. Secure the
hood and connector body together then connect the earth wire to the hood. Stick an identifying label on to
the connector hood.
3. For each Klippon connector, wire up the connector then stick an identifying label on it.
4. Check the wiring thoroughly against the schedule and wiring diagram.
5. Attach all connectors to the Rear Panel.
Refer to Chapter 2 and Appendix C for examples of field transmitter connections and a full list of the 7951’s pin
identities.
5.9 Step 6: Earthing the instrument
Caution:
Incorrect earthing can cause many problems, so you must earth the chassis and the
electronics correctly. The way in which you do this depends almost entirely on the type of
installation you have and the conditions under which it operates. Therefore, because these
instructions cannot cover every possible situation, the manufacturers recommend that
earthing procedures should only be carried out by personnel who are skilled in such work.
The chassis of the 7951 must be earthed in all cases; both for safety reasons and to ensure that the installation
complies with EMC regulations. Do this by connecting an earth lead from the stud on the rear panel (Figure 4.6)
to a local safety earth such as a cabinet earth or some other suitable metal structure. If there is more than one
7951, see Figure 4.7 for correct and incorrect methods.
In addition to earthing the chassis, you may have to make extra earth connections in some cases, depending on
the installation requirements. Details of internal earthing arrangements are in Appendix C.
Earth
lead
Crinkle
washers
Plain
washers
Nut
Thumb
nut
Figure 4.6: The 7951’s Earth Stud