APC AP9340 manual Installation-Accessories, How to wire Modbus

How to wire Modbus

The Modbus interface supports 2-wire RS-485, plus ground. Modbus can be configured to communicate at either 9600 or 19200 bps. The default setting is 9600 bps.

Modbus requires both termination and polarization resistors at the bus master. Each end of the bus requires a 150-ohm resistor, and the bus also requires

a400–650-ohm resistor from D1 to +5 Vdc and from D0 to GND.

SHIELD

TO

GND

UNIT 2

GD D N 0 1 D

SHIELD

TO

GND

CONTROLLER

+5V GND D0 D1

499 OHM

499 OHM

TWISTED

PAIR

D0 & D1

UNIT 1

G D D

N 0 1

D

TWISTED

PAIR

D0 & D1

150 OHM

aem0069a

For more information, see the Modbus standard at www.modbus.org. Search for the Modbus Serial Line Implementation Guide.

Installation—Accessories

Sensors

Selecting a location for the sensor:

Install the sensor in a location that represents the air to be monitored. Avoid placing the sensor anywhere that may affect the sensor reading, such as near windows, room entrances, air ducts, other heat sources, or in direct sunlight.

Environmental Manager: Main Module 9