Chapter 7 ___________________________________________________  Retrieving Data Messages
VAISALA______________________________________________________________________ 103
Command format: aI!
The response:
a13ccccccccmmmmmmvvvxxxxxxxx<cr><lf>
Example:
0I!013VAISALA_WXT530103Y2630000<cr><lf>
Start Measurement Command (aM)
This command asks the device to make a measurement. The measured 
data is not sent automatically. You must request it with the Send data 
command aD. 
The host device is not allowed to send any commands to other devices 
on the bus until the measurement is completed. 
When several devices are connected to the same bus and simultaneous 
measurements from the many devices are needed, use start concurrent 
measurement aC or start concurrent measurement with CRC aCC, see 
the next sections.
where
a = Device address
I = Send identification command
! = Command terminator
where
a = Device address
13 = The SDI-12 version number, indicating SDI-12 
version compatibility; for example, version 1.3 is 
encoded as 13
cccccccc = 8-character vendor identification Vaisala_
mmmmmm = 6 characters specifying the sensor model number 
vvv = 3 characters specifying the firmware version
xxxxxxxx = 8-character serial number 
<cr><lf> = Response terminator