Exlar Curtiss-Wright Tritex II Series, Installation And Service Manual

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Curtiss-Wright | TRITEX II AC 75 Rev. K PN61928 7/12/2022 57
Connecting multiple Tritex actuators to a Modbus Master Host
Important considerations
•
Always use 3 conductors, RS485 +, RS485 – and Reference.
• A twisted pair for 485+ and 485- is preferred.
• RS485 is a “multi-drop” network as opposed to a “star”, therefore
keep the drop (stub) to each actuator as short as possible. When
using the 8 mm connector use a T connector, such as the Exlar
PN TT458SP.
•
A termination resistor is not usually required.
IA4 Option board connections
4-20 mA Isolated I/O, IA4 Option
The IA4 option board replaces the standard I/O board and provides
one 4-20 mA isolated analog input and one 4-20 mA isolated analog
output; these I/O circuits are isolated from each other as well as all other
actuator I/O, grounds and commons. The IA4 option also includes four
isolated digital inputs and three isolated digital outputs; this is a reduction
from the eight inputs and four outputs available on the standard I/O
board.
The 4-20 mA input is a two wire circuit. A small amount of power from
4-20 mA signal is used to generate the internal power supplies needed
for the isolation of the input section. This allows the input to float with the
Transmitter or loop power supply without inference from the other
Actuator grounds or commons. The power supply starts up when the
input reaches 3mA. When the 4-20 mA loop is unpowered, the software
reads an off-scale high value that should be configured to indicate a
“Loss of Signal” condition.
Modbus Master
PC, HMI, PLC etc
Tritex 1 Tritex 2 Tritex (n)
(32 max)
485+ 485- Ref