User Manual

Make Measurement Command: M!
The make measurement command signals a measurement sequence to be performed. Data values generated in
response to this command are stored in the sensor's buffer for subsequent collection using “D” commands. Data
will be retained in sensor storage until another “M”, “C”, or “V” command is executed. M commands are shown in
the following examples:
Command
Response
Response to 0D0!
aM! or aM0!
a0011<cr><If>
Returns µmol m
-2
s
-1
using electric light calibration
aM1!
a0011<cr><If>
Returns millivolt output
aM2!
a0011<cr><If>
Returns µmol m
-2
s
-1
using sunlight calibration
aM3!
a0011<cr><If>
Returns immersed µmol m
-2
s
-1
for underwater measurements with electric light
calibration
aMC0!
a0011<cr><If>
Returns µmol m
-2
s
-1
using electric light calibration w/CRC
aMC1!
a0011<cr><If>
Returns millivolt output w/ CRC
aMC2!
a0011<cr><If>
Returns µmol m
-2
s
-1
using sunlight calibration w/ CRC
aMC3!
a0011<cr><If>
Returns immersed µmol m
-2
s
-1
for underwater measurements with electric light
calibration w/ CRC
where a is the sensor address (“0-9”, “A-Z”, “a-z”) and M is an upper-case ASCII character.
The data values are separated by the sign “+”, as in the following example (0 is the address):
Command
Sensor Response
Sensor Response when data is ready
0M0!
00011<cr><lf>
0<cr><lf>
0D0!
0+2000.0<cr><lf>
0M1!
00011<cr><lf>
0<cr><lf>
0D0!
0+400.0<cr><lf>
0M2!
00011<cr><If>
0<cr><If>
0D0!
0+2000.0<cr><If>
0M3!
00011<cr><If>
0<cr><If>
0D0!
0+2000.0<cr><If>
where 2000.0 is µmol m
-2
s
-1
and 400.0 is mV.
Concurrent Measurement Command: aC!
A concurrent measurement is one which occurs while other SDI-12 sensors on the bus are also making
measurements. This command is similar to the “aM!” command, however, the nn field has an extra digit and the
sensor does not issue a service request when it has completed the measurement. Communicating with other
sensors will NOT abort a concurrent measurement. Data values generated in response to this command are stored
in the sensor's buffer for subsequent collection using “D” commands. The data will be retained in the sensor until
another “M”, “C”, or “V” command is executed:
Command
Response
Response to 0D0!
aC! or aC0!
a00101<cr><lf>
Returns µmol m
-2
s
-1
using electric light calibration
aC1!
a00101<cr><lf>
Returns millivolt output
aC2!
a00101<cr><lf>
Returns µmol m
-2
s
-1
using sunlight calibration
aC3!
a00101<cr><lf>
Returns immersed µmol m
-2
s
-1
for underwater measurements with electric
light calibration
aCC! or aCC0!
a00101<cr><lf>
Returns µmol m
-2
s
-1
using electric light calibration w/CRC
aCC1!
a00101<cr><lf>
Returns millivolt output w/CRC
aCC2!
a00101<cr><lf>
Returns µmol m
-2
s
-1
using sunlight calibration w/CRC
aCC3!
a00101<cr><lf>
Returns immersed µmol m
-2
s
-1
for underwater measurements with electric
light calibration w/CRC