Xylem H-312-22 - Manual (Page 30)

4-10 SDI-12 Command and Response Protocol H-312
4.10 Extended Read/Write Stage_Offset and Read/Write Stage_Slope
The H-312 processes the pressure sensor input and computes Pressure in PSI units. Stage is
computed with a Stage = m * Pressure + b equation. The Slope (m) and Offset (b) terms are
programmable, allowing the user to scale the reading into other engineering units. These
commands allow the user to read or write (change) the Stage_Slope and Stage_Offset terms. The
slope is set to 2.3067 and the offset to 0.00 at the factory. With the factory default (2.3067) the
Stage will be in units of water depth (in feet). The new values are stored in non-volatile EEPROM
within the sensor. Once the new Stage_Slope or Stage_Offset value is written to the EEPROM, a
copy is sent to the sensor data buffer for verification. This data can be viewed by using a
subsequent "D" command. To verify these settings any other time, use the "XRS" or “XRO”
commands. This command takes 001 seconds to complete and places 1 value in the data buffer.
Use the “aD0" command to collect and view the new slope or offset.
Command Response Description
"aXRS!" “a0011" Read StageSlope
"aXRO!" “a0011" Read StageOffset
"aXWSddd!" “a0011" Write StageSlope
"aXWOddd!" “a0011" Write StageOffset
Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
XRS are upper case characters.
XRO are upper case characters.
XWS are upper case characters.
XWO are upper case characters.
ddd is the new slope or offset value (For example: 20.0, 195)
Example of a H-312 Extended "Read Stage_Slope" command:
Command
Response Time Values Description
"aXRS!" "a0011" 1 sec 1 Read StageSlope
Command Response Description
"aD0!" "a+1.00" StageSlope is 1.00
Example of a H-312 Extended "Write Stage_Slope" command:
Command
Response Time Values Description
"aXWS1.234!" "a0011" 1 sec 1 Write StageSlope
Command Response Description
"aD0!" "a+1.234" StageSlope is 1.234