Bronkhorst®
Instruction Manual EL-PRESS™
9.17.101I
27
3.6.2
Digital operation (RS232)
Digital operation via RS232 or fieldbus (RS485) adds extra features to the instrument, such as:
·
Direct reading with a readout/control module or host computer
·
Diagnostics
·
·
Adjustable minimum and maximum alarm limits (
)
Make sure that the instrument’s baud rate matches the baud rate of the master/application, otherwise no communication
can be established. See section
for changing baud rate, node address and parity setup.
For RS232 communication, the maximum cable length is 10 m for baud rates up to 38400 Baud. For higher baud rates,
use cable lengths of maximum 3 m.
·
If the 9-pin D-sub connector is set for RS-485 communication, the instrument will not respond when connected to an
RS-232 configuration. In that case, use the power-up functionality of the
mode and enable RS-232 communication.
·
After configuring the required parameters, use the same procedure to leave configuration mode and restore the original
communication settings (otherwise, configuration mode remains enabled after power down).
For more information about communication through the RS232 interface, consult the
RS232 manual
(document no.
9.17.027).
3.6.2.1
FlowDDE
Digital Bronkhorst® instruments can be operated via RS-232 using the Bronkhorst® FlowDDE server application. Dynamic
Data Exchange (DDE) provides a basic level of inter process communication between Windows applications. Together with a
client application, either self-made or with a third party SCADA program, it is possible to create an easy way of data
exchange between the flow meter/controller and a Windows application. For instance, a cell in a Microsoft Excel
spreadsheet can be linked to the measured value of an instrument; FlowDDE updates the cell automatically when the
measured value changes.
FlowDDE uses specific parameter numbers for communicating with the instrument. A DDE parameter number is a unique
number in a special FlowDDE instruments/parameter database and not the same as the parameter number from the process
on an instrument. FlowDDE translates the node-address and process number to a channel number.
DDE-client applications communicate with the FlowDDE server by using DDE messages. Before messages can be exchanged,
a DDE link has to be made. A DDE link consists of three parts: the server, the topic and an item. For separation the characters
'|' and '!' may be used, so a DDE link in e.g. Microsoft Excel becomes: Server|Topic!Item.
For standard instrument parameters and the FlowDDE server, these are:
·
Server: FlowDDE or FlowDDE2
·
Topic: ‘C(X)’ for channel number X
·
Item: ‘P(Y)’ for parameter number Y
An example of a DDE link in a Microsoft Excel cell is =FlowDDE|’C(1)’!’P(8)’ to read parameter 8 of channel 1.
When not using FlowDDE for communication with the
instrument, parameters are addressed by:
·
Node address of the instrument
·
Process number on the instrument
·
Parameter number on the instrument
See section
instrument parameters.
For more information about FlowDDE, including setting up a DDE link, consult the
FlowDDE Manual
(document no.
9.17.067) or the help file in the application.
