Vaisala WXT520 - Manual (Page 54)

User’s Guide ______________________________________________________________________
52 __________________________________________________________________ M210906EN-C
- PTU measurement adds approximately 0.8 mA to the standby
consumption. Each single measurement of PTU takes 5 seconds
(including the warm-up period). This can be used for estimating the
average consumption of PTU.
- Continuous precipitation adds some 0.07 mA to the standby
consumption. A single, isolated raindrop causes an additional
0.04 mA to the standby consumption, this condition lasting about
10 seconds (continued, if more raindrops are detected within the
10-second period).
- ASCII RS-232 Standby consumption with baud rates 4800 and
higher is typically 0.24 mA. With a low baud rate selection (1200
or 2400 Bd) this is reduced to less than 0.19 mA. The jumper wires
across TX+/RX+ and TX-/RX- add an extra 0.02 mA (they are
necessary only in 2-wire RS-485 mode).
- ASCII RS-232 Polling mode and Automatic mode have equal
consumption. Thus Automatic mode is a little more economic,
since interpreting the poll takes more prosessing time than starting
the Automatic message. However, care should be taken when
selecting Precipitation Autosend mode, where the submodes M=R
and M=C may cause extra consumption in rainy conditions, as
triggered to send messages by the rain incidents.
- ASCII RS-232 Data transmission adds 1 ... 2 mA to the standby
consumption during the message sending time. Also it should be
noted that the host device's input (data logger or PC) may
constantly draw some current from the TX line.
- RS-485 and RS-422 Data interfaces consume about the same as
RS-232. But with long data cables the consumption during data
transmission may be much higher, especially when termination
resistors are used. On the other hand, the RS-485 driver is in high
impedance state when not transmitting - thus in idle state no current
can be drawn by the host input.
- NMEA modes consume about the same as ASCII modes.
- SDI-12 Native mode (M=S, C=1) has the lowest standby
consumption, about 0.1 mA. Note that it can also be used with RS-
232 terminals (PC or equivalent), see the SDI-12 connection
diagram in
Figure 25 on page 50 . In this case the commands must
be in SDI-12 format, but no special line break signals are required.
The SDI-12 mode is for polling only.
- SDI-12 Continuous mode (M=R) consumes about the same as the
ASCII RS-232 mode.