Vaisala WXT510 - Manual (Page 69)

Chapter 7 __________________________________________________ Getting the Data Messages
VAISALA _______________________________________________________________________ 67
SDI-12 Protocol
There are two different modes available for providing all the
functionality of the SDI-12 v1.3 standard.
The lowest power consumption is achieved with the Native SDI-12
mode (aXU,M=S), as it makes measurements and outputs data only
when requested. In this mode all the commands presented in this
chapter are available except those for the Continuous measurement.
In the Continuous mode (aXU,M=R) measurements are made at user-
configurable update intervals, see
Chapter 8, Sensor and Data Message
Settings, on page 93 . The data is outputted on request. In this mode all
the commands presented in this chapter are available.
For changing the message parameters, units and other settings, see
Chapter 8, Sensor and Data Message Settings, on page 93 .
In the Native SDI-12 mode (aXU,M=S) the WMT50 is in idle state
most of the time (power consumption < 1 mW). More power is
consumed only during the measurements and data transmit requested by
the host device. Especially, the wind measurement typically consumes
60 mW average power (with 4 Hz sampling rate), throughout the
averaging period. In the Continuous mode (aXU=M,R) the power
consumption is determined by the internal update intervals of the
sensors and wind averaging time. These have certain limits, so very
long measurement intervals can not be achieved with this mode. Also
the power consumption between the measurements is about three times
that of the Native mode.
Address Query Command (?)
This command is used to query the address of the device on the bus.
If more than one sensor is connected to the bus, they will all respond,
causing a bus collision.
Command format: ?!
where
?
= Address query command
! = Command terminator