Xylem H-4280 - Manual (Page 27)

H-4280
SDI-12 Command and Response Protocol 3-15
3.12 Extended Read Mean_Count and Write Mean_Count
The H-4280 can make up to 700 measurements/second (per 8-channels) The module makes
multiple high speed measurements, averages the results (simple mean) and reports one
measurement per channel. The number of samples (Mean_Count) can be programmed from 1 to
65535, the H-4280 comes from the factory configured to make 100 samples for each channel (100
x (1/700)=0.142 seconds ). The number of samples per measurement (1-65535) is the same for all
8-channels.
The ttt field in the SDI-12 sensor response is computed by the H-4280 and indicates how much
time the H-H4280 will require to complete the measurement sequence. The ttt field will
automatically change if Mean_Count is changed.
The default ttt field is computed internally by the H-4280 as follows:
Warmup time +1.0 sec
Raw Measurements: +.142 sec (1/700 x 100)
Math Overhead: +1.0 sec
Round Upwards +1.0
- - - - - - -
ttt 3.0 Seconds
Use the “aXRMC!” and “aXWMC!” extended commands to monitor or change the number of
samples taken for each SDI-12 measurement.
Once a new Mean_Count value is written, a copy is sent to the sensor data buffer for verification.
This data can be viewed by using a subsequent "D" command. To read or verify the value any
other time, use the "XRMC" command.
Command Response Description
"aXRMC!" “a0011" Read Mean_Count
"aXWMCnnn!" “a0011" Write Mean_Count
Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
XRMC are upper case characters.
XWMC are upper case characters.
nnn is the number of raw measurements wanted
This command takes 001 seconds to complete and places 1 value in the data buffer. Use the
“aD0" command to collect and view the current value.