BRONKHORST EL-FLOW Base Series User manual

Instruction manual
EL-FLOW Base series
Mass Flow Controllers
Doc. no.: 9.17.061N Date: 08-04-2019
ATTENTION
Please read this instruction manual carefully before installing and operating the instrument.
Not following the guidelines could result in personal injury and/or damage to the equipment.

BRONKHORST®
Page 2 EL-FLOW Base Series Mass Flow Controllers 9.17.061
Even though care has been taken in the preparation and
publication of the contents of this manual, we do not
assume legal or other liability for any inaccuracy, mistake,
mis-statement or any other error of whatsoever nature
contained herein. The material in this manual is for
information purposes only, and is subject to change
without notice.

BRONKHORST®
9.17.061 EL-FLOW Base Series Mass Flow Controllers Page 3
TABLE OF CONTENTS
Contents
1General Product Information...........................................................................................................5
1.1 Introduction.......................................................................................................................................................5
1.2 Intended Use...................................................................................................................................................... 5
1.3 Symbols.............................................................................................................................................................. 5
1.4 Product Support References.............................................................................................................................. 5
1.5 Warranty............................................................................................................................................................ 6
1.6 Product Description ........................................................................................................................................... 6
1.6.1 General Description ....................................................................................................................................6
1.6.2 Model Key................................................................................................................................................... 7
1.6.3 Seals............................................................................................................................................................ 7
1.6.4 Calibration...................................................................................................................................................8
1.6.5 Features ...................................................................................................................................................... 8
1.7 Operating Principles...........................................................................................................................................9
1.7.1 Thermal Gas Flow Sensor Principle............................................................................................................. 9
1.7.2 Bypass Principle ..........................................................................................................................................9
1.7.3 Solenoid Valve Principle............................................................................................................................ 10
1.8 Maintenance....................................................................................................................................................10
2Installation Instructions................................................................................................................. 11
2.1 Introduction.....................................................................................................................................................11
2.2 Unpacking and inspection................................................................................................................................ 11
2.3 Rated pressure test inspection ........................................................................................................................ 11
2.4 Instrument mounting....................................................................................................................................... 11
2.5 Fluidic connections .......................................................................................................................................... 12
2.6 In-line filter usage ............................................................................................................................................ 12
2.7 Piping requirements ........................................................................................................................................12
2.8 Electrical connections ......................................................................................................................................13
2.8.1 Interface.................................................................................................................................................... 13
2.8.2 Power Supply ............................................................................................................................................ 13
2.9 Power and warm-up ........................................................................................................................................ 13
2.10 Pressure supply / Start-up ............................................................................................................................... 13
2.11 System purging ................................................................................................................................................14
2.12 Zeroing............................................................................................................................................................. 14
3Basic Operation............................................................................................................................. 15
3.1 General ............................................................................................................................................................ 15
3.2 Analog operation ............................................................................................................................................. 15
3.3 Digital communication protocol detection (Flow-BUS RS232 or MODBUS RS485) ......................................... 16
3.4 Basic RS232 Flowbus operation .......................................................................................................................17
3.5 Modbus RS485 operation ................................................................................................................................ 18
3.5.1 Modbus termination.................................................................................................................................18
3.5.2 Slave address, baud rate and parity setup................................................................................................ 19
3.5.3 Implementation class................................................................................................................................ 23
3.5.4 Response time........................................................................................................................................... 23
3.5.5 Supported Modbus functions ................................................................................................................... 23
3.5.6 Available parameters ................................................................................................................................ 24
3.6 Push-button operation .................................................................................................................................... 26
3.7 Micro-switch use for reading/changing control mode ....................................................................................27
3.7.1 Read control mode ...................................................................................................................................27
3.7.2 Change control mode: .............................................................................................................................. 27
3.8 LED indications................................................................................................................................................. 28
3.9 Basic Parameters and Properties..................................................................................................................... 29
3.9.1 Introduction .............................................................................................................................................. 29
3.9.2 Basic Parameters....................................................................................................................................... 30
4Advanced Operation ..................................................................................................................... 31
4.1 Reading and Changing Instrument Parameters............................................................................................... 31

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Page 4 EL-FLOW Base Series Mass Flow Controllers 9.17.061
4.1.1 Introduction .............................................................................................................................................. 31
4.1.2 Identification.............................................................................................................................................31
4.1.3 Fluid Information ...................................................................................................................................... 32
4.1.4 Auto Zeroing .............................................................................................................................................32
4.1.5 Controller Response Adjustment..............................................................................................................33
4.1.6 Changing Default Control Mode ...............................................................................................................34
4.1.7 Display Filter ............................................................................................................................................. 35
4.1.8 Disabling Micro Switch.............................................................................................................................. 35
4.2 Using other gasses than specified.................................................................................................................... 36
4.2.1 Software for conversion factor calculation............................................................................................... 36
4.2.2 Maximum pressure drop........................................................................................................................... 36
5Troubleshooting............................................................................................................................ 37
5.1 General ............................................................................................................................................................ 37
5.2 LED indications................................................................................................................................................. 37
5.3 Troubleshooting summary general.................................................................................................................. 37
6Removal and Return Instructions................................................................................................... 39
7Service.......................................................................................................................................... 40

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1General Product Information
1.1 Introduction
This user guide covers the EL-FLOW Base Series mass flow controllers for gasses as shown in the pictures
below. Included herein is product information, installation instructions, operation, maintenance,
troubleshooting and technical specifications.
F-201CB F-201AB F-202BB
8 mln/min –20 ln/min 20 ln/min –70 ln/min 70 ln/min –200 ln/min
1.2 Intended Use
The intended use of EL-FLOW Base instruments is to control gas flow rates of the specified gas noted on
the instrument label. The gas has to be clean.
The instruments can be used for either (fast) switching or controlling a constant flow rate.
1.3 Symbols
Important information. Discarding this information could cause injuries to people or damage to the
Instrument or installation.
Helpful information. This information will facilitate the use of this instrument.
Additional info available on the internet or from your local sales representative.
1.4 Product Support References
Instructions:
Operating instructions digital instruments, document nr. 9.17.023.
RS232 interface with FLOW-BUS protocol, document nr. 9.17.027.
Technical drawings:
Hookup EL-FLOW Base, document nr. 9.16.091
Dimensional drawing F-201AB, document nr. 7.15.1
Dimensional drawing F-201CB, document nr. 7.15.166
Dimensional drawing F-202BB, document nr. 7.15.170
These documents can be found at:
http://www.bronkhorst.com/en/downloads

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Page 6 EL-FLOW Base Series Mass Flow Controllers 9.17.061
1.5 Warranty
The products of Bronkhorst® are warranted against defects in material and workmanship for a period of
three years from the date of shipment, provided they are used in accordance with the ordering
specifications and the instructions in this manual and that they are not subjected to abuse, physical
damage or contamination.
Products that do not operate properly during this period may be repaired or replaced at no charge.
Repairs are normally warranted for one year or the balance of the original warranty, whichever is the
longer.
See also paragraph 9 of the Conditions of sales.
The warranty includes all initial and latent defects, random failures, and undeterminable internal causes.
It excludes failures and damage caused by the customer, such as contamination, improper electrical
hook-up, physical shock etc.
Re-conditioning of products primarily returned for warranty service that is partly or wholly judged non-
warranty may be charged for.
Bronkhorst High-Tech B.V. prepays outgoing freight charges when any party of the service is performed
under warranty, unless otherwise agreed upon beforehand, however, if the product has been returned
collect to Bronkhorst High-Tech B.V., these costs are added to the repair invoice. Import and/or export
charges, foreign shipping methods/carriers are paid for by the customer.
1.6 Product Description
1.6.1 General Description
An EL-FLOW Base mass flow controller consists of a thermal mass flow sensor, a laminar flow element
which acts as a bypass, a solenoid proportional control valve and a digital electronic PC-board for PID-
control and communication.
PC-Board
Mass Flow
Sensor
Laminar Flow
Element
9pin SubD
Connector
Control Valve
Body
There are three different basic models for different flow rates (F-201CB, F-201AB and F-202BB).
Within each model there is variation in laminar flow element size, orifice size and sealing material. These
variables are optimized for the customer’s gas and process conditions.

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1.6.2 Model Key
Example: F-201CB-200-ABD-00-V
Range: 200 ml/min
Analog output: 0-10Vdc
Seals: Viton
1.6.3 Seals
The instrument is fitted with either Viton or Kalrez seals. Which sealing material is used is shown in the
last character of the model key.
Bronkhorst® has gathered a material compatibility chart from a number of sources believed to be
reliable. However, it is a general guide only. Operating conditions may substantially change the accuracy
of this guide. Therefore there is no liability for damages accruing from the use of this guide.
The customer’s application will demand its own specific design or test evaluation for optimum reliability.
Check if the seals like O-rings, plunger and packing gland of capillary are suitable for the used gas and
process.

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1.6.4 Calibration
EL-FLOW Base instruments are Air or N2 calibrated. Bronkhorst® certifies that all instruments meet the
rated accuracy. They have been calibrated using measurement standards traceable to the standards of
the Dutch Metrology Institute (VSL).
The calibration is converted to the customer’s gas and conditions using a detailed conversion model.
This conversion adds a level of calibration uncertainty.
Thumb rule for calculating the conversion uncertainty is typical:
Uncertainty < 2% x CF for CF > 1
Uncertainty < 2% / CF for CF < 1
With CF defined as the approximate conversion factor, which can be calculated with:
2
1
2
1





p
p
C
C
CF
in which:
n
p
C
specific heat
n

density at normal conditions
(1) calibration fluid (Air or N2)
(2) customer fluid
Check FLUIDAT® on http://www.fluidat.com
FLUIDAT® is a collection of routines to calculate physical properties of gases and liquids. These routines
are made available at the FLUIDAT® on the Net website.
EL-FLOW Base instruments are standard delivered without calibration certificate. Calibration certificates
can be ordered together with the instruments. Contact your local sales representative for more
information.
1.6.5 Features
Each instrument consists of an Analog interface, a digital RS-232 interface and a digital ModBus/RS485
interface. The analog and the digital interface can be used together at the same time.
According to the pin-designation both RS232 and Modbus/RS485 are assigned to the same pins. When
connecting these pins to either of the two, the instrument will automatically detect which protocol to
use.
Digital operation adds a lot of extra features (compared to analog operation) to the instruments.
Such as:
setpoint slope (ramp function on setpoint for smooth control)
direct reading at readout/control module or host computer
several control/setpoint modes (e.g. purge/close valve)
identification (serial number, model number, device type, user tag)
adjustable controller settings for custom controller response

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1.7 Operating Principles
1.7.1 Thermal Gas Flow Sensor Principle
The gas flow sensor operates on a principle of heat transfer by sensing the temperature difference along
a heated section of a capillary tube. Part of the total flow is forced through the capillary by means of a
laminar flow element in the main stream generating a pressure difference.
The design of the laminar flow device is such that flow conditions in both the capillary and laminar flow
device are comparable, thereby resulting in proportional flow rates through the meter. The delta-T
sensed by the upstream and downstream temperature sensors on the capillary depends on the amount
of heat absorbed by the gas flow.
The transfer function between gas mass flow and signal can be described by the equation:
mpsignal cKV 
Vsignal = output signal
cp= specific heat
K = constant factor
m= mass flow
Thermal sensor in a bridge configuration
The temperature sensors are part of a bridge circuit. The imbalance is linearised and amplified to the
desired signal level.
1.7.2 Bypass Principle
The measurement part of an EL-FLOW Base consists of a thermal sensor and a laminar flow element
(LFE). A laminar flow element consists of a stack of discs with precision etched flow channels. The flow
through each channel is proportional to the flow through the sensor. In this way, by adding more or less
laminar flow discs, the total flow rate of an instrument can be adjusted while using the same sensor flow
rate.
In general instruments with these sensors may be mounted horizontal, as well as in a vertical position, at
low operating pressures.
Sensor flow
10 mln/min Air
LFE(4x) flow
10 mln/min Air
10 mln/min Air
10 mln/min Air
10 mln/min Air
Example of a 50 mln/min measurement part
V
s
i
g
n
a
l

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1.7.3 Solenoid Valve Principle
The control valve used in the EL-FLOW Base series is a standard, direct operated control valve. It is a
normally closed solenoid valve. The plunger is lifted by the force of the magnetic field of the coil. The
diameter of the orifice under the plunger is optimised for the customer’s application.
flowcontrol
valve
The control valve is not designed to provide positive shut-off. It is recommended to install a separate
shut-off valve in the line if so required. Also pressure surges, as may occur during system pressurisation
must be avoided.
1.8 Maintenance
No routine maintenance is required to be performed on the controllers when they are used with clean
gas.
Units may be flushed with clean, dry inert gas.
In case of severe contamination it may be required to clean the inside of the instrument. After cleaning a
recalibration is needed. Bronkhorst® has a trained staff of servicemen available. Contact your local
supplier for cleaning and recalibration options.
If the equipment is not properly serviced, serious personal injury and/or damage to the equipment
could be the result. It is therefore important that servicing is performed by trained and qualified service
personnel.

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2Installation Instructions
2.1 Introduction
This chapter discusses how to prepare the system and install an EL-FLOW Base mass flow controller.
2.2 Unpacking and inspection
Check the outside packing box for damage incurred during shipment. Should the packing box be
damaged, then the local carrier must be notified at once regarding his liability, if so required. At the
same time a report should be submitted to your distributor.
Carefully remove the equipment from the packing box. Verify that the equipment was not damaged
during shipment. Should the equipment be damaged, then the local carrier must be notified at once
regarding his liability, if so required. At the same time a report should be submitted to your distributor.
Refer to chapter 6, Removal and Return Instructions, about return shipment procedures.
Before installing an EL-FLOW Base it is important to read the attached label and check:
- Flow rate
- Fluid to be measured
- Up- and downstream pressures
- Input/output signal
- Temperature
Do not discard spare or replacement parts with the packing material and inspect the contents for
damaged or missing parts.
2.3 Rated pressure test inspection
Each EL-FLOW Base is pressure tested to at least 1.5 times the working pressure of the process
conditions stipulated by the customer, with a minimum of 8 bar.
Pressure testing sticker
Each instrument is helium leak tested to at least 210-9 mbar l/s Helium outboard.
The tested pressure is stated on the flow controller with a RED COLOURED sticker. Check test pressure
before installing in the line.
If the sticker is not available or the test pressure is incorrect, the instrument should not be mounted in
the process line and be returned to the factory.
2.4 Instrument mounting
The bottom side of an EL-FLOW Base consists of two mounting holes for stable mechanical fixation of
the instrument. Refer to the following documents for exact position of the mounting holes.
Dimensional drawing F-201AB, document nr. 7.15.165.
Dimensional drawing F-201CB, document nr. 7.15.166.
Dimensional drawing F-202BB, document nr. 7.15.170.
The preferred mounting position of EL-FLOW Base mass flow controllers is horizontal. Other mounting
positions may introduce a zero shift and/or little gas and pressure dependency of the zero signal. When

BRONKHORST®
Page 12 EL-FLOW Base Series Mass Flow Controllers 9.17.061
mounting an instrument other than horizontal, zeroing of the instrument is advised. The zeroing
procedure is described in chapter 2.12.
Avoid installation in close proximity of mechanic vibration and/or heat sources.
2.5 Fluidic connections
The fluid connections of EL-FLOW Base instruments consist of ¼” BSPP female thread. The adapter
chambers are optimised for the use of Swagelok RS-type adapters combined with AS013 (70°Sh) o-rings
for leak tight installation.
Bronkhorst® highly recommends the use of Swagelok RS-type stainless steel adapters, e.g. part number
SS-400-1-4RS.
Adapters can be ordered separately to the instruments. Contact your local distributor for more
information.
Always check your system for leaks, before applying fluid pressure. Especially if toxic, explosive or other
dangerous fluids are used.
2.6 In-line filter usage
Fluids to be measured should be absolutely free of dirt, oil, moisture and other particles. Fluids that are
heavily contaminated or contain particulates are detrimental to precision. If liquid phases enter the
sensor chamber, the function of the sensor and the mass flow controller may be impaired.
It is recommended to install an in-line filter or liquid separator upstream of the flow controller, and if
backflow can occur, a downstream filter is recommended too. Be aware of the pressure drop caused by
the filter.
Contact your distributor for further information.
2.7 Piping requirements
Be sure that piping is absolutely clean!
DO NOT install small diameter piping on high flow rates, because the inlet jet flow will affect the
accuracy.
DO NOT mount abrupt angles direct on in- and outlet, especially not on high flow rates. At least 10 pipe
diameters distance between the angle and the instrument is recommended.
DO NOT mount pressure regulators direct on the inlet of gas flow meters/controllers, but allow some
meters of piping (at least 25 pipe diameters).

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9.17.061 EL-FLOW Base Series Mass Flow Controllers Page 13
2.8 Electrical connections
2.8.1 Interface
EL-FLOW Base instruments can be operated by means of:
1. Analog interface (0...5Vdc or 0...10Vdc or 0...20mA or 4...20mA)
2. RS232 interface with FLOW-BUS protocol
3. RS485 interface with Modbus protocol
All above operation options are standard available in EL-FLOW Base instruments.
According to the pin-designation both RS232 and RS485 are assigned to the same pins. When connecting
these pins to either of the two, the instrument will automatically detect which protocol to use. When
sending a frequent request to the instrument, it will be capable of recognising the protocol,
once the instrument detect this protocol, it will send an answer.
The instrument will remember the detected protocol as long as the instrument is powered. This auto
detection can not be switched off or by-passed.
For electrical hook-up diagrams refer to document 9.16.091, “Hook-up EL-FLOW Base”
This documents can be found at:
http://www.bronkhorst.com/en/downloads
2.8.2 Power Supply
EL-FLOW Base controllers are powered with +15 Vdc to +24 Vdc.
When providing your own power supply be sure that voltage and current rating are according to the
specifications of the instrument(s) and furthermore that the source is capable of delivering enough
power to the instrument(s). Refer to Hookup EL-FLOW Base, document nr. 9.16.091, for more details.
Bronkhorst® recommends the use of their standard cables. These cables have the right connectors and if
loose ends are used, these will be marked to prevent wrong connection.
When using other cables, cable wire diameters should be sufficient to carry the supply current and
voltage losses must be kept as low as possible. When in doubt: contact your distributor.
EL-FLOW Base instruments carry the CE-mark. Therefore they have to comply with the EMC
requirements as are valid for these instruments. However compliance with the EMC requirements is not
possible without the use of proper cables and connector/gland assemblies.
!
When connecting the system to other devices (e.g. to PLC), be sure that the integrity of the shielding is
not affected. Do not use unshielded wire terminals.
2.9 Power and warm-up
Before switching on power, check if all connections have been made according to the hook-up diagram.
It is recommended to turn on power before applying pressure on the instrument and to switch off
power after removing pressure.Check fluid connections and make sure there is no leakage. If needed
purge the system with a proper fluid. Only purging with gases is allowed. Turn on power and allow at
least 30 minutes warming up and stabilizing. During warm-up period, fluid pressure may either be on or
off.
2.10Pressure supply / Start-up
When applying pressure to the system, take care to avoid pressure shocks in the system and increase
pressure gradually up to the level of the actual operating conditions.

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Page 14 EL-FLOW Base Series Mass Flow Controllers 9.17.061
2.11System purging
If explosive gases are to be used, purge the process with inert dry gas like Nitrogen, Argon etc. for at
least 30 minutes.
In systems with corrosive or reactive fluids, purging with an inert gas is absolutely necessary, because if
the tubing has been exposed to air, introducing these fluids will tend to clog up or corrode the system
due to a chemical reaction with oxygen or moist air.
Complete purging is also required to remove such fluids from the system before exposing the system to
air. It is preferred not to expose the system to air, when working with these corrosive fluids.
2.12Zeroing
The zero point of each instrument is factory adjusted. However, the zero point may shift slightly due to
temperature, pressure, gas type and mounting position influences. If so required, the zero point of the
instrument may be re-adjusted.
Zeroing is possible over RS232 Flowbus, RS485 ModBus or by means of using the micro switch. Zeroing
by means of using the micro switch is described in this manual.
Warm-up, pressure up the system and fill the instrument according to the process conditions.
Make sure no flow is going through the instrument by closing valves near the instrument.
The setpoint must be zero.
Press the micro switch and hold it. After a short time the red LED will go ON and OFF, then the green
LED will go ON. At that moment release the micro switch.
The zeroing procedure will start at that moment and the green LED will blink fast. The zeroing
procedure waits for a stable signal and saves the zero. If the signal is not stable zeroing will take long
and the nearest point to zero is accepted. The procedure will take approx. 10 sec.
When indication is showing 0% signal and the green indication LED is burning continuously again,
then zero has been performed well.
For information how to start the zeroing procedure over RS232 FlowBus or RS485 ModBus check
chapter 4.1.4, “Auto Zeroing”

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3Basic Operation
3.1 General
An EL-FLOW base instrument can be operated by means of:
Analog interface (0...5Vdc/0...10Vdc/0...20mA/4...20mA)
Digital RS232 Flowbus interface (connected to COM-port by means of special cable on 38400 Baud)
Digital RS485 Modbus interface.
Operation via analog or digital interface can be performed at the same time. A special parameter called
“control mode” indicates to which setpoint the controller should respond.
3.2 Analog operation
At analog operation following signals are available:
measured value (analog output)
setpoint (analog input)
The type of installed analog interface (0-5V, 0-10V, 0-20mA or 4-20mA) can be found in the model key of
the instrument. Refer to paragraph 1.6.2.
Setpoints below 2% of the full scale will be interpreted as 0% setpoint.
When operating the instrument through the analog interface it is possible to connect the instrument
simultaneously to RS232 or Modbus/RS485 for reading/changing parameters (e.g. controller response
or other fluid selection).

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Page 16 EL-FLOW Base Series Mass Flow Controllers 9.17.061
3.3 Digital communication protocol detection
(Flow-BUS RS232 or MODBUS RS485)
According to the pin-designation both RS232 and RS485 are assigned to the same pins.
At each power-on of the EL-Flow Base instrument the digital communication protocol from the master (PLC/PC)
must be detected by the EL-Flow Base instrument. This auto detection cannot be switched off or by-passed.
Description
PLC / PC
PLC / PC
Valid answer
within 100 ms
No
Initialisation
Send request to
read the
Measure value
Protocol Detected
Yes
Wait 100 ms
Bronkhorst
HIGH-TECH
R
Ruurlo - Holland
Base
EL-FLOW
mass flow meter/controller
received data is
recognized within
particular
frame?
No
Valid message
received within 660 ms?
Protocol Detection
in EL-FLOW Base
RS232 FLOW-BUS 110 ms
RS485 Modbus-RTU 110 ms
RS485 Modbus-ASCII 110 ms
Protocol and time frame (ms)
Detected Protocol 660 ms
Yes
Protocol Detected
Yes
No
Answer is sent
At each power-on of the
EL-Flow Base instrument a
protocol detection routine
is started and the
communication lines switch
each 110 ms between
RS232 FLOW-BUS, RS485
Modbus-RTU and RS485
Modbus-ASCII .
If received data is recognized
within the particular time
frame of a protocol then it
will immediately switch to
this protocol for 660 ms.
If now a valid message is
received the instrument will
answer (reply) to this
message and stay in the
detected protocol.
The protocol is detected.
The instrument will
remember the detected
protocol as long as the
instrument is powered.

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3.4 Basic RS232 Flowbus operation
RS232 Flowbus communication can be used for operating your instrument using the Bronkhorst®
FLowDDE server application.
Physical layer and communication protocol are detected automatically upon reception of messages.
These messages must be sent using the correct combination of physical layer and communication
protocol. After every power-up the communication detection mode is active.
Dynamic Data Exchange (DDE) provides the user a basic level of inter process communication between
Windows applications.
FlowDDE is a DDE server application. Together with a client-application, either self-made or with a
SCADA-program from 3rd-parties, it is possible to create an easy way of data exchange between the flow
controller and a Windows application.
For example, a cell in Microsoft Excel could be linked to the measured value of the flow controller and
when the measured value changes, it will be automatically updated in the Excel spreadsheet.
Examples of DDE client applications: FlowPlot, FlowView, MS-Office, LabView, Intouch, Wizcon.
The FLowDDE server also offers a lot of test facilities and user adjustable settings for efficient
communication with the connected flow controller.
How to setup a DDE link with FlowDDE is described in the help-file of the FlowDDE application.
Programming examples are available for making applications in: Visual Basic, LabView and Excel.
FLowDDE parameter numbers:
Reading/changing parameter values via FLowDDE offers the user a different interface to the instrument.
Besides the application name: ‘FLowDDE’ there is only need of:
topic, used for channel number: ‘C(X)’
item, used for parameter number: ‘P(Y)’
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.
Node-address and process number will be translated by FLowDDE to a channel number.
FlowDDE and other Bronkhorst® applications are available at the Bronkhorst download site:
http://www.bronkhorst.com/en/downloads
Base
FlowDDE
server
Application 1
Application 2
Application n
RS232
DDE-link
DDE-link
DDE-link
Windows based Personal Computer
Instrument

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Page 18 EL-FLOW Base Series Mass Flow Controllers 9.17.061
A special RS232 cable (7.03.366) can be ordered separately. It consists of a T-part with 1 male and 1
female sub-D 9 connector on one instrument-side and a normal female sub-D 9 connector on the side of
the computer. By means of this cable it is possible to offer RS232 communication and still be able to
connect power-supply and analog interface through the (analog) sub-D 9 connector.
3.5 Modbus RS485 operation
This chapter is limited to the description of the interface between the Modbus Mass Flow Controller
with a master device. It will explain how to install an EL-FLOW Base instrument to your Modbus system.
It only contains the information that is needed most.
The implementation of the Modbus interface is based on the following standards:
[1] MODBUS Application Protocol Specification V1.1b, December 28, 2006
[2] MODBUS over Serial Line specification and implementation guide V1.02
There is no mutual communication between Modbus slaves; only between master and slave.
More detailed information about Modbus can be found at http://www.modbus.org or any website of
the (local) Modbus organisation of your country (when available).
Physical layer and communication protocol are detected automatically upon reception of messages.
These messages must be sent using the correct combination of physical layer and communication
protocol. After every power-up the communication detection mode is active.
3.5.1 Modbus termination
The Modbus must be terminated correctly with termination resistors (RT1, RT2) and biasing resistors
(RB1, RB2).
EL-FLOW®Base
mass flow meter/controller
EL-FLOW®Base
mass flow meter/controller
EL-FLOW®Base
mass flow meter/controller
D1 Modbus (B/B’)
D0 Modbus (A/A’)
+
-
RT1
121 Ohm
RB2
392 Ohm
RB1
End termination
Begin termination
Supply Voltage
Remark: See hookup diagram for details
RB1 value depends on supply voltage
Supply Voltage RB1
+5V 392 Ohm
+10V 1210 Ohm
+15V 2210 Ohm
+24V 3480 Ohm
RT2
121 Ohm
Bronkhorst® advices the following resistor values for the following voltages:
Supply voltage
termination
Bias Pull-up resistor
RB1
Termination resistor
RT1 & RT2
Bias Pull-down resistor
RB2
+5V
392 Ohm
121 Ohm
392 Ohm
+10V
1210 Ohm
121 Ohm
392 Ohm
+15V
2210 Ohm
121 Ohm
392 Ohm
+24V
3480 Ohm
121 Ohm
392 Ohm

BRONKHORST®
9.17.061 EL-FLOW Base Series Mass Flow Controllers Page 19
Termination resistors: RT1 and RT2
The termination resistors RT1 and RT2 must be placed only at the extreme ends of the data line (see
schematics above). The resistance value should be equal to the characteristic cable impedance. In case
of common cabling this should be:
RT1 = 121 Ohm
RT2 = 121 Ohm
Remark: RT1 and RT2 should be larger than 90 Ohm.
Biasing resistors: RB1 and RB2
The biasing resistors RB1 (pull-up) and RB2 (pull-down) must be added.
RB1 must be connected between the Supply Voltage (Us) and D1 Modbus (B/B'). The resistance value of
RB1 depends on the applied supply voltage, and is:
RB1 (Us = +24V) = 3480 Ohm
RB1 (Us = +15V) = 2210 Ohm
RB1 (Us = +10V) = 1210 Ohm
RB1 (Us = +5V) = 392 Ohm
RB2 must be connected between the D0 Modbus (A/A') and ground. The resistance value of RB2 is:
RB2 = 392 Ohm
3.5.2 Slave address, baud rate and parity setup
Default instruments will be delivered to customers on address 1 and with a baud rate of 19200 baud and
EVEN parity.
The slave address, baud rate and parity of the Bronkhorst® meter/controller Modbus slave can be
changed to fit the instrument in your existing Modbus network. Changing the slave address, baud rate
and parity can be done in the following ways.
Using RS232: FlowDDE
‘Off-line’ via the RS232 communication port by means of FlowDDE. This program can be used to
read/change parameters, including the slave address, baud rate and parity.
Connect your Bronkhorst®
meter/controller Modbus slave instrument to a free COM-port using the special cable with on one side
a T-part with male and female sub-D 9 connector and on the other side a female sub-D 9 connector (part
number 7.03.366). The single sub-D 9 connector should be connected to your COM-port and the female
sub-D 9 of the T-part to the male sub-D 9 of the instrument. Standard cables are approx. 3 meters.
Maximum length between PC and instrument allowed is approximately 10 meters.
Start FlowDDE and open communication via the menu (as shown below) or by pressing <F3>.

BRONKHORST®
Page 20 EL-FLOW Base Series Mass Flow Controllers 9.17.061
Once the DDE server is active, open the FlowDDE Test Form via the menu (as shown below) or by
pressing <F6>.
The following screen appears:
To read/change the slave address, parameter 199: Bus address must be selected. To read/change the
baud rate, parameter 201: Baudrate must be selected. And to read/change the parity parameter 335:
Bus1 Parity must be selected. To change one of these parameters parameter 7: Initreset has to be set to
‘64’ first.
Valid values for the slave address are between 1 and 247, valid values for the baud rate are 9600, 19200
and 38400, valid values for parity are 0 (= None), 1 (= Odd) and 2 (= Even). The changed values will be
effective immediately after changing.
In case of OEMD2 hardware revision (“OEMD2” text on the instrument label):
To read/change the slave address, parameter “309: Fieldbus2 address”must be selected. To
read/change the baud rate, parameter “310: Fieldbus2 baudrate”must be selected. And to read/change
the parity parameter “336: Fieldbus2 parity must be selected”. To change one of these parameters
parameter “7: Initreset”has to be set to ‘64’ first.