Wiring The Serial Port; Wiring The Modbus Communications Line (Optional) - GE Measurement Sentinel LCT4 User Manual

2.7.4 Wiring the Serial Port

The flow transmitter is equipped with a built-in serial communications port. This port is user-selectable to be either an
RS232 or RS485 port. For more information on serial communications refer to the EIA-RS Serial Communications
Manual (916-054). The use of 12-24 AWG (3.3 - 0.2 mm
and a minimum 18 AWG (1.5 mm
2.7.4a Wiring the Serial Interface
To wire the serial port, refer to Figure 35 on page 51 and complete the following steps:
1. Disconnect the main power to the meter and remove the wiring access cover.
2. Install the required cable gland in the chosen conduit hole of the electronics enclosure.
3. Feed one end of the cable through the cable gland, wire it to terminal block TB2, and secure.
Attention European Customers! To meet CE Mark requirements, all cables must be installed as
described in Appendix B, CE Mark Compliance.
4. If the wiring of the unit has been completed, reinstall the wiring access cover and tighten the set screw.

2.7.5 Wiring the Modbus Communications Line (Optional)

The Sentinel LCT4 uses the RS485 interface with Modbus communications protocol for a maximum line distance up to
4000 ft (1200 m). GE recommends using shielded 18-24 AWG (0.82 - 0.2 mm
impedance of 120 ohms, with 120-ohm termination at each end of the communications line. This interface is also
user-configurable as an RS232 interface.
Connect the two leads and the shield of the Modbus line to the NET section of terminal block TB2 in the flowmeter.
See Figure 17 on page 35, Table 11 on page 45 and Figure 35 on page 51.
Sentinel™ LCT4 User's Manual
2
) is recommended for two conductors per terminal.
TB2
T (RS485–)
R (RS485+)
COM
SEN 898
Figure 22: Serial Connections
2
) twisted pair wiring is recommended for single conductors,
Network Interface
TD (–)
RD (+)
SGND (COM)
2
)) cable having a characteristic
Chapter 2. Installation
39