Siemens SITRANS F Modbus RTU RS 485 - Connecting the Modbus Module; Terminal Allocation and Specifications

Connecting
4
On the electrical termination boards for USM-II transmitters, additional input/output terminals
have been reserved for add-on module functions. The numbering range of these terminals is as
follows, but how many are actually used depends on the type of add-on module.
Additional terminals reserved for add-on modules:
• MAG 6000: 91 - 97
• MASS 6000: 91 – 100
Note
The standard inputs and outputs continue to function and are not a󹪜ected by the presence
of an add-on module. Any existing transmitter electrical connections remain undisturbed.
The MASS 6000 with extra outputs, i.e. 3 current outputs, cannot be extended with an add-
on module
WARNING
Only authorized personnel are allowed to carry to carry out work on electrical connections.
Please refer to the relevant product operating instruction for other electrical connection
information.
Note
Shielding
Always shield a Modbus over Serial Line Cable. At one end of each cable its shield must be
connected to protective ground. If a connector is used at this end, the shell of the connector is
connected to the shield of the cable.
Note
Cable speci󹪝cations
A RS 485-Modbus must use a balanced pair (for D0-D1) and a third wire (for the ground
reference). For the balanced pairs used in an RS 485-system, a Characteristic Impedance with a
value between 100 and 120 Ohms must be used.
Modbus RTU RS 485
Operating Instructions, 03/2021, A5E00753974-AB 17