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LabVIEW drivers - Bronkhorst FLOW-BUS
Bronkhorst controllers and indicators using FLOW-BUS
Bronkhorst controllers and indicators are great instruments to control the flow of gasses and liquids. These instruments can be addressed through various protocols such as DeviceNet™, Profibus-DP®, Modbus or FLOW-BUS. This document describes a LabVIEW driver for direct communication with FLOW-BUS devices.
The FLOW-BUS protocol is described in short here and a full description can be found in the instruction manual 'RS232 interface with FLOW-BUS protocol for digital multibus Mass Flow / Pressure instruments' (doc. 9.17.027Q).
Using LabVIEW with FLOW-BUS devices goes like this:
The FLOW-BUS protocol defines some 330 parameters but the driver addresses just 2: write setpoint and read process value. that, if defined for a specific device, can either be read or written or that can both be read and written. The presented LabVIEW driver can be used for the 2 most common parameters: setpoint and process value. Additional parameters, such as valve position, can easiliy be added.
What should be known for each device is its node number and its nominal range. On the LabVIEW BlockDiagram there should should be a reference for each control (setpoint entry) and indicator (process value display).
The driver comes as a functional global which can perform the following 3 tasks: initialize, update and terminate. 'initialize' collects and stores the abovementioned parameters and then open the serial port. 'update' will update the setpoint of any device if the setpoint on screen has changed and updates the process value reading of each next device in each next call. 'terminate' sets all setpoints to 0 and closes the serial port.
The following sample shows how to implement the LabVIEW driver for 4 mass flow controllers.
The number of mass flow controllers can easily be expanded by putting more control and indicators on the FrontPanel and by expanding the arrays on the left side on de BlockDiagram.
Bart Boshuizen, 2012/09/27