Vaisala WXT510 - Manual (Page 45)

Chapter 5 _______________________________________________ Wiring and Power Management
VAISALA _______________________________________________________________________ 43
- Wind measurement is absolutely the most consuming operation
in the system. So, it all depends on how the wind is to be reported.
If long time averages are needed, the wind must be constantly
measured - then it makes no big difference, which requesting
period or mode is used. Fully continuous wind measurement with
4 Hz sampling rate adds 2 ... 5 mA to the standby current
(depending on the wind and some other climatic conditions). But
for instance 10 second average requested every 2 minutes
consumes 12 times less. And 1 Hz sampling rate makes it further
decrease to one fourth.
- PTU measurement adds approximately 0.75 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 0.19 mA. With a low baud rate selection (1200
or 2400 Bd) this is reduced by 28% to less than 0.14 mA. The
jumper wires across TX+/RX+ and TX-/RX- add an extra 0.01 -
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 a lot 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.