mainstream™

Mainstream Modbus Adapter

The Modbus Adapter is a device that is external to the Mainstream and works by connecting to the Mainstream communications port, allowing the customer to read measurement data using the Modbus RTU protocol. The Adapter can operate using Modbus RTU over RS232 or RS485 (half and full duplex), it can accept external power supplies and is currently available for use with fixed units.

Relays single or multiple measurements from the Mainstream.
Configurable for fast operation or power saving operation.
Built-in self-diagnostics.

Many popular products such as telemetry units and dataloggers incorporate Modbus communications. Many of these devices are already embedded throughout the water industry infrastructure, the Modbus Adapter bridges the gap between the Mainstream and these devices.

The Mainstream Modbus Adapter makes the reliability, accuracy and affordability of the Mainstream, available to anyone who already has this technology in place or is looking to upgrade their communications capabilities.

Benefits & Features

Capable of relaying single or multiple measurements from the Mainstream
Configurable for fast operation or power saving operation
Includes self-diagnostic functions
Multiple output configurations – RS232, RS485 Half Duplex and RS485 Full Duplex
Accepts auxiliary power supply input, power from the Mainstream or power from the Modbus master device
Quick to setup and configure

Measurement Principles

Mainstream uses the area-velocity method to give a continuous or time sample measurement of fluid flow. Mainstream uses a streamlined probe that operates immersed in the flowing liquid. The velocity probe transmits ultrasound into the liquid to create a zone of inspection. Bubbles and solid particles carried through this zone by the flow, even when present in only minute quantities, reflect ultrasound back to the probe.

The received ultrasound signal is processed to produce a histogram of the flow velocities. Analysing this histogram gives the mean flow velocity. Only signals containing verified velocity information are used, thereby ensuring measurement integrity.

Liquid level is measured by a submerged pressure transmitter or ultrasonic sensor. The flow cross-sectional area is deduced from the liquid level measurement and the stored description of the channel or pipe cross section. The flow rate is the flow velocity multiplied by the flow cross-sectional area.

Product Features

power supplies

Mainstream:	Mainstream units with appropriate firmware upgrade can power the Modbus adapter via the RS232 communications cable
Modbus:	Terminals for 4.5-18V power input supplied via the Modbus master
Auxiliary:	Terminals for 4.5-18V power input from an external power source
Isolation:	Mainstream system unit is isolated from the Modbus/auxiliary power inputs
Power consumption:	50mA maximum operating current

communications

Mainstream:	Male connector on 1m lead mates with Mainstream communications connector
Modbus:	Terminals for digitally-isolated RS232 and RS485 connections
RS232 Communications:	1200, 2400, 4800, 9600, 19200 (default), 38400, 57600 and 115200 baud rates. None, odd or even parity.
RS485 Communications:	Full or half duplex. 1200, 2400, 4800, 9600, 19200 (default), 38400, 57600 and 115200 baud rates. None, odd or even parity. Address range 1-247. ¼ unit load (48Ω)

user interfaces

Modbus configuration:	Two internal DIP switches to select RS232 or RS485 communication and full/half duplex when operating in RS485 mode
Address configuration:	Three internal 10 position digital encoders to set adapter address
Diagnostics:	Three external LEDs to indicate operating status