19
4 Connecting to power supply
FIBERTRAC 31 • Four-wire 4 … 20 mA/HART
62067-EN-211203
567
8
2
3
4
1
2
+
( )
(-)
1
Fig. 15: Adjustment and connection compartment (Ex-ia) with instruments with
intrinsically safe current output
1 Terminals for intrinsically safe signal output 8/16 mA/HART (Multidrop) ac-
tive
2 Contact pins for the display and adjustment module or interface adapter
3 Terminals for the external display and adjustment unit
4 Ground terminal
Ifinductiveloadsorstrongercurrentsareswitchedthrough,thegold
plating on the relay contact surface will be permanently damaged.
The contact is then no longer suitable for switching low-voltage
circuits.
Inductive loads also result from the connection to a PLC input or
output and/or in combination with long cables. It is imperative that you
takemeasurestoextinguishsparkstoprotecttherelaycontact(e.g.Z
diode) or the transistor or 8/16 mA output.
4.4 Connection - Summation
Tomeasurethelevelinveryhighvessels,multipleinstrumentscanbe
cascaded.
Cascading means that two or several instruments are connected
which can together cover a longer measuring range.
The instrument acts as Primary and all other instruments operate as
Secondaries.
The pulse rates of all instruments are summed in the Primary instru-
ment and converted into a common signal.
The Primary instrument must have the function "Level". For this pur-
pose,selectunderthemenuitem"Setup - Application" the function
"Level".
Set the address setting (MGC) on the Primary instrument to "99".
Forthis,theSecondaryinstrumentsmustbedenedas"Summation
Secondary". Select under the menu item " Setup - Application" the
function "Summation Secondary".
The address setting (MGC) on the Secondary instruments can be
freely selected. Only the address "99" is reserved for the Primary
instrument.
Adjustment and connec-
tion compartment - In-
struments with intrinsi-
cally safe current output
Connection to a PLC
Electronics and connec-
tion compartment - sum-
mation
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