Vaisala WXT520 - Manual (Page 87)

Chapter 7 __________________________________________________ Getting the Data Messages
VAISALA_______________________________________________________________________ 85
Start Measurement Command with
CRC (aMC)
Command format: aMCx!
This command has the same function as the aM but a three-character
CRC is added to the response data strings before <cr><lf>. In order to
request the measured data, Send data command aD should be used, see
the following sections.
Start Concurrent Measurement (aC)
This command is used when there are several devices on the same bus
and simultaneous measurements are needed from the devices, or if more
than nine (9) measurement parameters are requested from a single
device.
The measured data is not sent automatically and it should be requested
with separate Send data command aD. See
Examples of aM, aC and aD
Commands on page 88 .
NOTE For changing the message parameters, units and other settings, see
Chapter 8, Sensor and Data Message Settings, on page 107 .
NOTE When the measurement takes less than one second, the response part
two is not sent. In WXT520 this is the case in the precipitation
measurement aM3.
NOTE The maximum number of parameters that can be measured with aM
and aMC commands is nine (9). If more parameters are to be
measured, Start concurrent measurement commands aC and aCC
should be used (for which the maximum number of parameters to be
measured is 20), see the following sections.