Xylem H-4161 - Manual (Page 20)

3-4 SDI-12 Command and Response Protocol
H-4161
The “aM1!” command is similar to the “aM!” command, however it places additional information
in the sensor buffer. If a data parameter has not been captured, the message “no data” is placed in
the sensor buffer.
During debug and testing this feature is useful for determining if the H-4161 is properly and
reliably capturing the monitored parameter. The recommended test procedure is to configure the
data logger to make a H-4161 “aM1!” measurement at the completion of the sensor scan.
Configure the data logger to record both the captured measurement and the calculated (desired)
mA parameters. During the sensor scan the data logger first initiates a measurement and collects
measurement data from the sensor being monitored. The H-4161 independently captures and
processes the monitored parameter. At the completion of the sensor scan the data logger issues an
“aM1!” command to the H-4161 and collects the response. The captured parameter value should
always match the data value the data logger previously collected from the sensor. Examine the
logged data to make certain the data is being captured and processed into the proper mA setting.
Example of a H-4161 "aM1!" command:
Command Response Time Values Description
"aM!" "a0014" 1 sec 4 Make measurement
Subsequent Command Response
"aD0"
a+AA.AAA+BB.BBB+CC.CC+DD.DD
where: AA.AAA
= Most recent measurement (feet, inches, meters etc.)
BB.BBB = Calculated (desired) mA setting for this measurement
CC.CC = Current Min (low) data setting (see “aXRIL!” command)
DD.DD = Current Max (high) data setting (see “aXRIH!” command)