There are 2 modes available for providing the functionality of the SDI-12 v1.3 standard.
The native SDI-12 profile (aXU,M=S) offers the lowest power consumption 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. The data is outputted on request. In this mode all the commands presented in this chapter are available.
In the native SDI-12 mode (aXU,M=S) the transmitter 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.
In particular, 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 cannot be achieved with this mode. Also the power consumption between the measurements is about three times that of the native mode.
When using SDI-12 in the native mode together with specific data loggers, there is the possibility of intermittent communication problems and rain accumulation measurement problems. If such problems occur, Vaisala recommends using SDI-12 in the continuous mode.