B.7 Start measurement commands (aM!)
A measurement is initiated with the
M!
command. The response to each command has the form
atttn<CR><LF>
, where
a
= sensor address
ttt
= time, in seconds, until measurement data is available. When the data is ready, the sensor
notifies the data logger, and the data logger begins issuing
D
commands.
n
= the number of values returned when one or more subsequent
D
commands are issued. For
the
aM!
command, n is an integer from 0 to 9.
When the
aM!
is issued, the data logger pauses its operation and waits until either it receives the
data from the sensor or the time,
ttt
, expires. Depending on the scan interval of the data logger
program and the response time of the sensor, this may cause skipped scans to occur. In this case
make sure your scan interval is longer than the longest measurement time (
ttt
).
Table B-2: Example aM! sequence
0M!
The data logger makes a request to sensor 0 to start a measurement.
00352<CR><LF>
Sensor 0 immediately indicates that it will return two values within the
next 35 seconds.
0<CR><LF>
Within 35 seconds, sensor 0 indicates that it has completed the
measurement by sending a service request to the data logger.
0D0!
The data logger immediately issues the first
D
command to collect
data from the sensor.
0+.859+3.54<CR><LF>
The sensor immediately responds with the sensor address and the two
values.
B.8 Stopping a measurement command
A measurement command (
M!
) is stopped if it detects a break signal before the measurement is
complete. A break signal is sent by the data logger before most commands.
A concurrent measurement command (
C!
) is aborted when another valid command is sent to the
sensor before the measurement time has elapsed.
B.9 Send data command (aD0! … aD9!)
The Send Data command requests data from the sensor. It is issued automatically with every type
of measurement command (
aM!
,
aMC!
,
aC!
,
aCC!
). When the measurement command is a
M!
SoilVUE™10 Complete Soil Profiler
22
