Electrical Connections; Electrical Terminals; Command Input (4-20 M A) C; Compliance Voltage - Flowserve Logix 520MD Plus Series User Instructions

7 ELECTRICAL CONNECTIONS

7.1

Electrical Terminals

Limit Switch
Terminals 1-4 or
Terminals 1-6
Auxiliary Card
Slot 1 +
Slot 1 -
Slot 2 +
Slot 2 -
HART 4-20 mA
Input +
Input -
7.2 Command Input (4-20 mA)
Connection
The Logix 520MD+ 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 7: Terminal Diagram.
source, a HART filter may be required. See Figure 8: HART
Filter.
7.3

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 520MD impedance.
The Logix 520MD+ 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
520MD+, perform the calculation in the following equation.
The Available Voltage must be greater than 10VDC in order
to support the Logix 520MD. Also, see Table 1: Input Signal.
Equation 1
© Flowserve Corporation
User Instructions - Logix® 520MD+ Series Digital Positioner
Figure 7: Terminal Diagram
Depending on the current
Example:
The available voltage (12,5 V) is greater than the required
voltage (10.0 V) therefore, this system will support the Logix
520MD. The Logix 520MD has an input resistance equivalent
to 500 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 520MD+ terminals. This could cause
permanent circuit board damage
16
Field Trial Version – Printed October 28, 2011
FCD LGENIM0105-00
Housing EARTH Terminal
Internal
External