Chapter 4 _________________________________________________________________ Operation
VAISALA ________________________________________________________________________ 95
Operating LM21 through Maintenance Port
The following information is given for enabling operation of the LM21
through its maintenance terminal port in, for example, troubleshooting,
calibration, and operation checking situations.
In normal operation LM21 shall have its parameters set to the default
values and its communication line released (closed) to enable use by the
host processor FSC202. This enables the operation of the LM21 as a part
of FS11.
Serial Communication Settings
In this FS11 application the default settings of the serial communications
port are as follows:
- 9600 baud
- No parity
- 8 data bits
- 1 stop bit
Serial Transmission RS-232
For the RS-232 communication the Vaisala maintenance terminal cable
QMZ103 connects the LM21 signal wires to a standard PC/Laptop RS-
232 interface sub-D9 connector:
- RS-232 TxD
to PC sub-D 3/9
- RS-232 RxD
to PC sub-D 2/9
- GND
to PC sub-D 5/9
Vaisala recommendation for the maximum length of the RS-232 cable is
50 m. Usually, the RS-232 connection can be used with distances up to
100 m without problems but that cannot be guaranteed.
Any computer equipped with terminal emulation software or a VT100-
compatible terminal with RS-232 serial interface can be used as a
Maintenance Terminal for LM21.
