Vaisala PWD22 - Ames; Mes

USER'S GUIDE ____________________________________________________________________
58 __________________________________________________________________ M210543EN-F
PWD22/52 does not echo the polling character string.
The answer message format is the following:
S
H
PW id
S
X
text
E
X
C
R
L
F
The ID has a two-character field because it can be two characters long.
An example of the polled (and automatic) message 0 format is the
following:
S
H
PW 1
S
X
00 500 700
E
X
C
R
L
F
PWD22/52 waits about 100 ms before it transmits the polled message to
give the host time to switch the RS-485 line to the receive mode.
For
compatibility in the system level, PWD22/52 also accepts FD instead
of PW in the polling
commands because the data message formats and
framing are the same as in the VAISALA FD12 and FD12P
sensors. If
PWD22/52
is polled by
C
R
E
Q
FD 1 2
C
R
, the answer starts with
S
H
FD 1
S
X
..
Precipitation Sums
PWD22/52 has no internal clock for automatic resetting of the sum data
at certain times. This can be done by the host with the following
command:
E
C
PW 0 C
C
R
where
E
C
=
ESC (ASCII character 1B hex).
C
R
=
Carriage Return (13 hex.)
PWD22/52 responds to the accepted command with the ASCII character
<
A
K
(06 hex).
The host computer can also maintain its own sum calculated from the
continuous PWD22/52 data. This may be safer, if the PWD22/52 power
breaks often and resets the sums before the scheduled time. The water
sum automatically resets when it reaches 99.99 mm and the snow sum at
999 mm.