Flowserve 500+ Series Logix - Manual (Page 22)

User Instructions - Logix® 500+ Series Digital Positioners FCD LGENIM0105-10 11/13
flowserve.com 22
7 ELECTRICAL CONNECTIONS
7.1 Electrical Terminals
Figure 23: Terminal Diagram
7.2
Command Input (4-20 mA)
Connection
The Logix 500+ is reverse polarity protected, however, verify
polarity when making field termination connection. Wire 4-20
mA current source to the input terminal labeled “HART 4-
20mA INPUT”. See
Figure 23: Terminal Diagram. Depending on the current
source, a HART filter may be required. See 18.1
Troubleshooting Guide.
7.2.1 Compliance Voltage
Output compliance voltage refers to the voltage limit the
current source can provide. A current loop system consists of
the current source, wiring resistance, barrier resistance (if
present), and the Logix 500+ impedance.
The Logix 500+ requires that the current loop system allow
for a 10 VDC drop across the positioner at maximum loop
current. The operating current range is from 3.8 to 24 mA.
In order to determine if the loop will support the Logix 500+,
perform the calculation in the following equation. The
Available Voltage must be greater than 10VDC in order to
support the Logix 500+. Also, see Table 1: Input Signal.
Example:
DCS Controller Voltage = 19 𝑉
Equation 1
Available Voltage = Controller Voltage (@Current
𝑚𝑎𝑥
) −
Current
𝑚𝑎𝑥
× (R
barrier
+ R
wire
)
Current
max
= 20𝑚𝐴
R
barrier
= 300𝛺
R
wire
= 25𝛺
Available Voltage = 19 V − 0.020 A × (300𝛺 + 25𝛺 )
Available Voltage = 12.5 V
The available voltage (12.5 V) is greater than the required
voltage (10.0 V) therefore; this system will support the Logix
500+. The Logix 500+ has an input resistance equivalent to
500 Ω at a 20 mA input current.
CAUTION: The current must always be limited for 4-20
mA operation. Never connect a voltage source directly
across the Logix 500+ terminals. This could cause
permanent circuit board damage.
Limit Switch
Terminals 1-6
Auxiliary Cards
Slot 2
-
Slot 2
+
Slot 1
+
Slot 1 -
HART 4-20 mA
Input +
Input -
Housing EARTH Terminal
Internal
External