Vaisala PWD22 User Manual page 76

User's Guide _______________________________________________________________________
74____________________________________________________________________ M210543EN-B
The system asks the following:
UPDATE CONFIGURATION PARAMETERS
UNIT ID (2 CHAR) ( 1)
If the PWD22 unit is named by one or two character ID codes, the
OPEN and polling commands use it as a parameter. The ID code is
also included in the data message heading. ID 1 is used as a default in
the message heading, if no other ID is given. The current ID can be
removed by pressing the hyphen ( - ) as an answer to the question.
In multidrop configuration, where several sensors are on the same
communication line, the units are differentiated by the ID.
The next CONF parameters are hardware or system dependent. They
can be changed from the factory set values for better performance or
maintenance purposes. The example configuration session is
explained in the following.
The currently measured offset value (not a parameter) is shown in the
brackets.
OFFSET ( 136.86) Y
OFFSET REFERENCE UPDATED
After receiving the Y answer, the system accepts the offset frequency
to be the reference parameter for hardware monitoring. The parameter
value is further compared with the current value to detect drift or other
failure in the optical signal measurement electronics.
Visibility alarm limits are checked to ensure that Limit 1 is higher
than Limit 2, and Limit 2 higher than Limit 3. Limit values are
expressed in meters.
ALARM LIMIT 1 (
ALARM LIMIT 2 (
ALARM LIMIT 2 UPDATED
ALARM LIMIT 3 (
In the example above, alarm Limit 2 gets a new value 300 m. When
the visibility now weakens below Limit 2, then the data message (0 ...
2) data status is set to 2. The visibility alarm is not shown in the
STAtus message
The alarm limits are also used to control the two (pull down) alarm
controls. Control 1 drives, when alarm 1 is on. Control 2 drives, when
alarm 2 is on. Control 3 drives, when alarm 3 is on. The controls are
1000)
200) 300
100)