4 Wiring Promag 53 PROFIBUS-DP/-PA
58 Endress+Hauser
4.4 Potential equalisation
4.4.1 Standard case
Proper measurement is only ensured when the fluid and sensor are at the same electri-
cal potential. The majority of Promag sensors have, as part of their standard configura-
tion, a built-in reference electrode, which ensures the required potential equalisation. As
a rule, this is sufficient to eliminate the need for ground disks or other measures.
Promag W:
Reference electrode is standard
Promag P:
Reference electrode is optional, depending on material
Promag H:
• No reference electrode. The metallic process connection provides a permanent elec-
trical connection to the fluid.
• If the process connections are made of a synthetic material, ground disks have to be
used to ensure that potential is equalised (see Page 38). Ground rings are optional
accessories, which must be ordered separately
→ Page 111.
Note:
When installed in metal pipes, we recommend that the transmitter housing's ground ter-
minal be connected to the pipe.
Fig. 36: Potential equalisation by means of the transmitter's ground terminal
Caution:
If the sensor does not have a reference electrode or metallic process connections, the
potential equalisation must be established in the manner described in the following spe-
cial cases. These special measures are in particular necessary when the usual ground-
ing is not ensured or when it is likely that there will be an excessive equalisation current.
F06-5xxxxxxx-04-xx-xx-xx-002
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