Chapter 1: Using Modbus with the InnovaSonic 205i
Overview
The flow meter comes standard with a RS-485 multi-drop and RS-232 point to point connection. RS-232 can be
used for point to point (one master one slave 205i) communication with wire runs of 50 feet or less. The RS-485
can be used to communicate over 1,000 meters, baud rate dependent with several 205i slaves on one wire pair.
This could be up to 30, 205is on one RS-485 segment, and 127 on a whole RS-485 network.
Both RS-485 and RS-232 communication can be used with the Modus RTU protocol. The network address
identifying code (IDN) is set in Menu 46. Although RS-232 doesn’t normally use an address, when using the
Modbus protocol it does.
When using digital commutations the analog current loop and OCT output of flow meter can be free to be used to
control the opening of a control valve. The relay output can be used to power-on/off other equipment. The analog
input of the system can be used to input signals such as pressure and temperature. These analog values can be read
using the Modbus RTU protocol to be used by customer software..
RS-232(<50 ft.) or RS-485 (up to 4,000 ft.) can be directly used for data transmission link for a short distance.
Current loop, radio transmission and modems can be used in medium or very long distance transmission.
When the flow meter is used in a network environment, various operations can be performed at the host device,
except for programming of the address identification code, which needs to be done at the flow meter keyboard.
The command answer mode is used in data transmission, i.e. the host device issues commands and the flow meter
answers correspondingly.
ATTENTION
RS-232 and RS-485 serial communications cannot be used at the same time.
1.1.
RS-232 / RS-485 Pin Definitions
Flow Meter:
PC COM Port:
TXD receive
Pin 2 Rx
RXD send
Pin 3 Tx
GND
Pin 5 GND
Flow Meter:
RS-485
2
Wire
Network:
A
A (-)
B
B (+)
GND
GND
Note: A&B may need to be reversed
