27
Logix
®
520MD+ and 510+ Digital Positioners FCD LGENIM0105-15-AQ – 05/16
flowserve.com
7
ELECTRICAL CONNECTIONS
7.1 Electrical Terminals
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”. Tight-
en using 0.5 to 0.6 Nm torque. See Figure 25: Terminal Diagram.
Depending on the current source, a HART filter may be required. See
19.1 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 operat-
ing 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.
Equation 1
Available Voltage =Controller Voltage (@Current
max
) -
Current
max
x (R
barrier
+ R
wire
)
Current
max
= 20m
A
R
barrier
= 3 00
Ω
R
wire
= 25
Ω
Available Voltage = 19 V - 0.020 A × (300
Ω
+ 25
Ω
)
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.
a
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.