MASS-STREAM
TM
Instruction Manual D-6300
9.17.104B
– Date of issue: 2018-12
Page 7 off 34
2
DIGITAL INSTRUMENTS
2.1 General
The digital instruments of M+W Instruments GmbH are measurement devices for thermal
mass flow and control of gases. They are equipped with a digital electronic multi-bus
pc-board and consist of a micro-controller with peripheral circuitry for measuring,
controlling and communication. The flow signal is measured directly in the gas flow,
digitized and processed by means of the internal software (firmware). The measured and
processed values can be output through the analog interface or through the digital
communication line (RS232 or optional fieldbus interface). For controllers the setting for
the actuator is calculated by the firmware. The setpoint can be given through the
analogue interface or through the digital communication line.
Digital instruments have a lot of setting parameters for signal processing, controlling and
many extra features and thus a wide range in use. Reading and changing of these
settings is only possible via RS232 or a fieldbus, except for measured value, setpoint and
valve output, which is also possible through the analogue interface (depending on
parameter setting).
Digital instruments can be operated by means of the following options:
1. Analog interface (
0…5 Vdc / 0...10 Vdc / 4…20 mA / 0...20 mA)
2. RS232 interface (connected to COM-Port by means of special cable at 38400 Baud)
3. FLOW-BUS interface
4. PROFIBUS DP interface
5. DeviceNet
TM
interface
6. Modbus-RTU interface
Depending on the pre-settings options 1 and 2 are always present on multi-bus
instruments. An interface to any available fieldbus is optional.
