Series PC Manual V 1.0 - Rev. 3
– 03/01/01
DS Europe
23
10.7.1. TERMINATION
RESISTANCE
In the MULTI-DROP connection you need to connect two terminating resistors, one (if not
present) on the remote (card, computer, PLC, etc.) and one on the last transducer of the
chain (the transducers are not supplied with built-in terminating resistors).
The termination resistance value must be in the proximity of 120 Ohm (¼ of a watt).
The terminating resistor must never be put onto another transducer other than the last
one, so as not to lower the line impedance too much (
figure 11
).
figure 1
: Multi-drop connection
10.8. GROUNDING
Important:
The transducer must be grounded accordingly to the Regulations in force in
the country where it is used. These Regulations take priority to what is indicated in this
manual.
The transducer is fitted with input filters for power supply, for the analog output signals and
for digital signals. The use of such filters may be necessary depending on environmental
conditions in which the unit is installed.
In order for these filters to operate correctly, the transducer needs to be connected to a
ground free from interference produced by other equipments.
Figure 12
shows how to ground the transducer. This connection must be done with a
conductor connected to a tag (2) of the shortest possible length and section (accordingly to
Regulations).
As an alternative, It is possible to connect the shield (3) or the measuring rod (1); it is very
important that it is only connected at one of these points to avoid ground looping.
WARNING : The common of the power supply ( “ - “ power supply ) must be grounded in
order to avoid damages due to mains fluctuations.
For further details see chapter 11 on electromagnetic interference.
