5. Commissioning, operation
The Modbus
protocol is a single-master protocol. This master controls the entire data
®
transfer and monitors any possible timeouts (no reply from the addressed instrument). The
connected instruments may only send telegrams after request by means of the master.
Modbus
RTU (RTU: Remote Terminal Unit) transmits the data in binary form, guarante-
®
eing a good data throughput.
Detailed information on the protocol under www.Modbus.org
5.4 Modbus
start-up kit
®
The gas density sensor, with the optionally available start-up kit (order no. 14075896),
can be configured for operation at the measuring location.
A further function is an integrated data logger, showing measured data in a specific
cycle or writing it in a file.
The start-up kit consists of:
Power supply unit
■
Interface converter (RS-485 to USB)
■
USB cable type A to type B
■
Sensor cable with M12 x 1 connector
■
Adapter cable for GDM-100-TI
■
Modbus
tool
®
■
5.4.1 Establish connection to the computer
Interface converter
RS-485
5.4.2 Modbus
tool
®
The software can be downloaded free of charge from the WIKA homepage: https://
de-de.wika.de/download_software_gas_density_sensors_de_de.WIKA
WIKA operating instructions gas density sensor, model GD-20
USB
Voltage supply
+
-
EN
17