Thermo Scientific LevelPRO Series, Installation Manual

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Wiring
Serial Communications
Thermo Fisher Scientific LevelPRO Installation Guide
4-7
The gauge provides one RS232 single drop and one RS485 multi-drop
serial interface. Screw terminal connectors for both ports are located at J3
on the CPU board.
The RS485 connector includes the +8 Vdc required to power the Thermo
Scientific 9734 handheld terminal (HHT) as well as the +DATA and
–DATA connections. An RJ11 (phone jack) connector is also provided for
the RS485 port at J4 on the CPU board. The HHT can be connected
directly to the RJ11 connector in safe areas.
Both ports provide independent access to the measurement readings and
software functions. They are always active and can be used to display
measurements. The setup menus, however, may only be accessed by one
port at a time.
Connecting the serial (COM) port on a PC to the RS485 port on the
gauge requires the RS485 / RS232 converter (p/n OTO515D).
1. Connect J3-12 (+DATA) and J3-11 (–DATA) to the corresponding
connections on the RS485 / RS232 converter.
2. Connect the converter to the PC using the supplied DB9 serial cable.
3. Refer to drawings 868519 and 868503 for additional details.
To communicate with multiple gauges via a RS485 party-line, each unit
must be assigned a unique unit identification number so it can be addressed
individually. All gauges are assigned unit number 0 (zero) by default.
To assign a unique unit number to each gauge, you must be able to
communicate with each one individually. Disconnect each gauge from the
party-line in turn and communicate with the disconnected gauge directly.
Alternately, you can remove power from all gauges except one and assign a
unit number to the powered gauge.
If you have trouble using another device on the RS485 chain, verify that it
is properly terminated for its position on the chain. To terminate a device,
connect a 120-ohm resistor between its RS485 + / - data terminals. Never
terminate more than the first and last device in the chain.
Serial
Communications
RS485 Wiring
Initial Setup for Party-
Line Communications