Spirax Sarco SP500 - Page 31

IM-P343-35 CTLS Issue 5
31
SP500 Electropneumatic Smart Positioner
6.2.3 Multi-loop applications Loop powered multi-positioner connections
Fig. 48
In a loop powered application, the 4-20 mA signal must be capable of supplying a minimum of 7 V per
positioner at 20 mA. In a split range application the signal source must be capable of supplying sufficient
voltage, i.e. 14 V is enough to power 2 positioners.
In case the SP500 smart valve positioner is equipped with the HART
®
board the voltage drop for each
positioner is 7.4 V instead of 7.0 V.
4 wires electrical connection
If the controller cannot supply the voltage needed, it is possible to power one or more positioner through an
external 24 V power supply connected to terminals 1 and 2.
In this way the voltage drop is about 1 V per positioner with an impedance of 50 Ohm.
3 4
Positioner 1
3 4
Positioner 2
1
Positioner 1
+
24 V
-
+
-
2 3 4 5 6 7 8 9 10
Current loop @ 8 V - (1 V + 7 V)
1
Positioner 2
2 3 4 5 6 7 8 9 10
Fig. 49 Split range with 2 positioners
Please note that for this conguration the PWS option board must be tted. The PWS option board can be
specied when the product is ordered or bought later and tted in situ - In this case reference Section 4.3
for mounting instructions.
+
4 - 20 mA signal @ 14 V minimum
-