Relays; Modbus Module; Host Computer Serial Communications; 2- Or 4-Wire Connection - ABB ScreenMaster RVG200 Operating Instructions Manual

ScreenMaster RVG200
Paperless recorder

3.7 Relays

One relay is provided as standard (position F). An additional relay module can be fitted in positions A, B, C
or D to provide 6 additional relays per module.
The maximum individual relay current is 5A. The total load for all relays within the recorder must not exceed
36 A.
Relay contacts are fitted with arc suppression components as standard.

3.8 MODBUS module

A MODBUS module can be fitted internally to the power supply board in position E to provide a 2- or 4-wire
isolated RS485 interface.

3.8.1 Host computer serial communications

The serial interface option module uses the MODBUS Remote Terminal Unit (RTU) Master / Slave protocol.
An appropriate RS422 / 485 communications driver must fitted to the host (Master) computer. It is strongly
recommended that the interface has galvanic isolation to protect the computer from lightning damage and
to increase signal immunity to noise pick-up.

3.8.2 2- or 4-wire connection

MODBUS serial communications must be configured as 2-or 4-wire serial links – see Figs 3.9 and 3.10,
respectively. The recorder must be added to the link configuration on the host system – refer to information
supplied with the host system.
Terminal block E
8
9
10
11
12
13
GND
Fig. 3.9 2-wire connection
OI/RVG200-EN
Rx/Tx +
Rx/Tx –
COM
Host computer
'B'
'A'
Tx +
+5 V
Tx –
1.8 k pull-up resistor
Rx +
'A'
Rx –
'B'
1.8 k pull-down resistor
GND
0 V
3 Installation
21