Appendix C. CS700H Operation Details
C-9
A sensor address is changed with command
aAb!
, where
a
is the current
address and
b
is the new address. For example, to change an address from
0
to
2
, the command is
0A2!
. The sensor responds with the new address
b
, which in
this case is 2.
Only one sensor should be connected to a particular terminal at a
time when changing addresses.
C.6.2.6 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 C-6
.
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.
C.6.2.7 Start Concurrent Measurement Commands (aC!)
A concurrent measurement (
aC!
) command follows the same pattern as the
aM!
command with the exception that it does not require the data logger to
pause its operation, and other SDI-12 sensors may take measurements at the
same time. The sensor will not issue a service request to notify the data logger
that the measurement is complete. The data logger will issue the
aD0!
command during the next scan after the measurement time reported by the
sensor has expired. To use this command, the scan interval should be 10
NOTE
