Xylem H-3531 FlashLite - Manual (Page 58)

5-20 SDI-12 Command and Response Protocol
H-3531
5.19 Extended Read Mean_Count and Write Mean_Count
The H-3531 FlashLite™ makes multiple raw sensor measurements, discards the high and low
values, integrates (averages) the measurement data and computes Pressure (PSI). The number of
raw sensor measurements made for each SDI-12 measurement sequence is programmable. When
measuring turbulent water, tides or other special applications Mean_Count can be changed to
increase or decrease the number of pressure measurements made during the SDI-12 measurement
sequence.
The H-3531 FlashLite™ makes 7.3 pressure measurements per second (137ms/ measurement).
The ttt field in the SDI-12 sensor response is computed by the H-3531 FlashLite™ and indicates
how much time the H-3531 FlashLite™ will require to complete the measurement sequence. The
ttt field will automatically change if Mean_Count is changed.
The H-3531 FlashLite™ comes from the factory with Mean_Count set to 8. The factory default
ttt field is computed internally by the H-3531 FlashLite™ as follows:
Raw Measurements: +1.1 sec (0.137 sec/measurement X 8 psi measurements)
Discarded Data:
+1.0 sec (Hi and Low values and warmup measurements)
Atmospheric Valve: +1.5 sec (Pressure settling time)
Atmospheric Offset: +1.1 sec (0.137 sec/measurement X 8 (4 psi, 4 temp) measurements)
Math Overhead:
+0.3 sec
Round Upwards +1.0
- - - - - - -
ttt 6.0 Seconds
The “aXRMC!” and “aXWMC!” extended commands allow the number of raw sensor
measurements for each SDI-12 measurement sequence to be monitored or changed.
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<cr><lf>" Read Mean_Count
"aXWMCn!" “a0011<cr><lf>" 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.
n 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.