Instruction Manual
DM08
When using pipes lined with electrical insulation, plastic tubing or concrete conduits, a separate
earthing washer is used to earth the measuring media. The earthing washer is installed between
the pipeline connection and the sensor’s flange and the ring’s inside contacts the media. Contrary
to the diagram shown below, one earthing washer on the inflow side is sufficient.
If bidirectional measurements are to be taken, one earthing washer must be installed on either
side.
Protection washers or protection rings can also be used as earthing component; or special earth-
ing electrodes, incorporated in the sensor, may be installed.
Earthing electrodes are more economical than earthing washers. However, it must be ensured that
noticeable differences in potential within the equipment are eliminated, otherwise the earthing elec-
trodes will electrolyze and be destroyed.
Potential-free installation of the sensor:
If the pipelines cannot be earthed, due to operational reasons, the sensor must be installed voltage
free. To do this, a separate cable must be used to electrically connect these segments of the
pipeline (min. 6mm²).
An electrical connection occurring between the sensor and any material used for the installation
must be avoided. Insulating segments must be installed between the sensor and the pipeline (e.g.
PVC pipes or similar).
Subsequently, earthing washers are used to electrically connect the media with the display elec-
tronics. The display electronics must not be connected with the protective earth conductor. This
may only be done, if the auxiliary power is 24 V
DC
.
Potential equalisation in separate design:
Create the potential equalisation in the separate design the same as described in the above sec-
tions. For the potential equalisation, the display electronics and the sensor are connected to each
other through Pin 7 of the connecting cable.
- 12 -
PKP Prozessmesstechnik • 09/2019
