RS485 interface extension

Note: The RS485 interface extension (301401) is an order option that cannot be ordered separately and installed by the customer himself.

The RS485 interface extension adds a galvanically isolated RS485 interface as well as a galvanically separated 5V sensor supply (max. 50mA ) to the 4-Channel Data Logger MBM . It can be used as an alternative to the onBoard RS485 interface if a galvanic isolation is necessary or if, besides a RS485 interface, all 4 universal inputs are also required. The control of the RS485 interface extension is carried out via the extension interface of the 4-Channel Data Logger MBM , which is then no longer available for other tasks.

Connecting sensors or devices with RS485 interface (view without power supply unit)

1 extension interface (7-pin JST connector) 3 Dip switch to switch on/off the terminal or clamp resistances
2 RS485 interface extension 4 (4-pin) connection terminals
Assignment of the connection terminals of theRS485 interface extension
GND Ground
A+ RS485 A
B- RS485 B
+5V Galvanically isolated 5V sensor supply (max.50mA )

In contrast to the onBoard RS485 interface, the 120Ω terminal resistance cannot be activated via the interface of the myDatanet server but must instead be activated via the 4-pin dip switch on the interface card. The clamp resistances can also be activated via this dip switch. The following table indicates the required settings for the switches.

Note: Only the combination of switch positions indicated in this table are permissible.

Dip switch to activate/deactivate the terminal or clamp resistances
S1 S2 S3 S4  
Off Off Off Off Neither terminal nor clamp resistance active
Off Off Off On 120Ω terminal resistance or RS485 A and RS485 B
On On Off Off 390Ω clamp resistances active
On On On Off 140Ω terminal resistaces and 390Ω clamp resistances active

Default settings upon delivery