Bronkhorst®
Instruction Manual EL-FLOW® Select
9.17.099J
30
3.6.1
Analog operation
With analog operation the following signals are available:
·
output signal: measured value
·
input signal: setpoint (controller only)
Setpoints below 2% of the full scale will be interpreted as 0%.
The analog interface type that is installed on the 9-pin D-sub connector can be found in the
of the instrument.
3.6.2
Digital operation (RS232)
Digital operation (e.g. via RS-232 or fieldbus) adds extra features to the instrument, such as:
·
Direct reading with a readout/control module or host computer
·
Diagnostics
·
Multi-range functionality
·
·
Adjustable minimum and maximum alarm limits (see
·
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 to an RS-232 master. In
to enter configuration mode and enable RS-232 communication.
·
After configuring the required parameters, follow the same procedure to leave configuration mode and restore the
original communication settings (otherwise, configuration mode will remain enabled after the next power-up).
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.
