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1. Introduction
The Modbus Unit has been specifically designed to work with Elster's A1140 and A1700
energy meters and fits under the terminal cover. The power supply of the unit is taken
directly from a A1140 and from an additional power adapter when used with the A1700.
The unit can be configured in one of three modes; modbus mode, transparent mode with
addressing and transparent mode without addressing.
2. Configuration
The configuration is done via the on-board DIP switch and terminal commands entered via
the RS232 port.
2.1. DIP Switch
The 8-way switch is divided into 3 groups as follows:
ON
1 2 3 4 5 6 7 8
Address
Modbus disabled
Meter type
2.1.1 Address
The address field is bit mapped and has a range of 1 to 31. Switching a bit position to the
on position will add the binary value to the address, e.g.
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
Calculate the address as follows:
Address = sum of value of bit positions set to on.
Each bit position has a value of 2
be:
0
2
Address = 2
+ 2
Address = 1
Address = 2
Address = 1 + 2 = 3
Address = 4
((bit position) – 1)
= 5
, so if position 1 and 3 is on the address will
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