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iTrans Fixed Point Single/Dual Gas Monitor ModBus Interface
(P/N: 77023554-1) iTrans User Manual 6-1
M
OD
B
US
I
NTERFACE
Chapter
6
6.1. Introduction
When programming the ModBus ID address on the electronics module
or on the smart sensor board, use the binary reference chart on the following page.
A “1” represents “ON” on the switch bank, and position 1 of the switch bank
represents the right most binary digit (LSB).
ModBus characteristics for the are listed below.
Table 6-1. ModBus Characteristics for the Gas Monitor
Characteristic Description
Hardware 2-wire mode (not 4-wire)
Baud Rate 9600
Electrical Standard TIA/EIA-485
Transmission Mode RTU mode (not ASCII)
Message Coding System 8-bit
Start Bits 1
Data Bits 8 (LSB sent first)
Parity Bits 0
Stop Bits 1
Important: When commissioning master and slave units on a ModBus network, it
is critical to ensure that every device on the ModBus network must have a unique
address. Otherwise, abnormal behavior of the entire serial bus can occur.
6.2. Sample Gas Reading via ModBus Network
To get a gas reading for Channel 1, you must read register 40102. This register
holds the gas reading in ppm.