METEK GmbH uSonic-2
3.2.1 Connection to a RS485- bus
It is recommended to connect the uSonic-2 to a RS422 or RS485 (4-wire)
interface of a computer before connecting to an RS485- bus (2-wire). All
settings that are scheduled for operation on the RS485-bus should be made
(i.e. sampling frequency, averaging time, etc.). The parameter EC should be
set to 0 (EC=0) to disable the reflection of the commands by the uSonic-2.
The last parameter of these settings should be the address of the uSonic-2.
By using parameter AD. The allowed range is 001 up to 254. (The address
has to be entered in a three digit format). The address 255 is reserved for all
connected uSonics to the bus.
(Look wildcard address).
Example:
AD=001 ENTER The user is setting the address to 001.
The device is just accessible with the address 001 now. The address has to
be embedded into two “#” signs.
Example:
#001#RD ENTER The user is asking for the latest dataset.
#001#Datensatz The uSonic-2 is displaying the latest dataset.
Now you can switch off the uSonic-2 and disconnect it from the computer and
connect it to the RS485 bus. If the RS485 bus operates in 2-wire technology,
please change the connection from 4-wire to 2-wire technology outside the
uSonic-2, directly at the connection to the bus. In general a terminating
resistor of 110Ω has to be connected to the RX and to the TX line at the first
and the last device of a bus.
3.2.2 Disable the RS485- mode
In case of maintenance jobs, calibration or software updates the uSonic-2 has
to be disconnected from the RS485 bus:
Switch off the uSonic-2 and disconnect it from the bus. Connect the uSonic-2
directly to a computer (RS422 or RS485 4- wire) and switch it on again.
At first disable the RS485- mode and set the address to 000:
#001#AD=000 ENTER The user is disabling the
RS485-mode.
Now the uSonic-2 is in the RS422- mode and can be calibrated or similar.
In this mode the uSonic-2 must not be connected to an RS485- bus!!
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