In-situ RDO Pro-X Owner's Manual page 29

Writes to these registers are only accepted if the probe is in the calibration mode. The probe will return
exception 0x85 (invalid device command sequence) if an attempt is made to write these registers when the
calibration mode is off.
0% Saturation Calibration Values
These values represent the sensor conditions while the probe is in a 0% saturation calibration environment.
These are not measured values, they are written by the controller during the calibration process.
Writes to these registers are only accepted if the probe is in the calibration mode. The probe will return
exception 0x85 (invalid device command sequence) if an attempt is made to write these registers when the
calibration mode is off.
Calibration Slope and Offset
These values represent the slope and offset that will be applied to the raw concentration reading from
the sensor to generate the final values reported by the sensor parameters. These registers may be written
independently of the normal internal calibration procedure.
Entering Calibration Registers
The sensor is calibrated using the following procedure.
1. Optional: Read the Sensor Data Cache Timeout register 9463 and store the value.
2. Write the Sensor Data Cache Timeout register 9463 to a value less than your intended sample rate
and greater than 1000 milliseconds. This will ensure that you get new sensor readings during the
stabilization process.
3. Optional: Read the temperature units register 0049 and saturation units register 0041 and store their
values.
4. Write the temperature units register 0049 to its default value (1) and write the saturation units
register 0041 to its default value (117).
5. Write the Calibration Mode On command (0xE000) to the sensor command register 9305.
6. Update the live salinity and barometric pressure registers if necessary.
7. Prompt the user to place the probe in a 100% saturation environment.
8. Read the oxygen concentration and temperature parameters. When these values have reached
equilibrium, record them in their respective 100% saturation calibration registers. Write the current
live salinity and barometric pressure readings to their respective calibration registers.
9. Place the sensor in a 0% saturation environment. When these registers have reached equilibrium,
record them in their respective 0% saturation calibration registers. If a zero calibration is not to be
performed, these registers can be set to zero or left at their previous values.
10. Write the Calibration Update command (0xE001) to the sensor command register. The sensor will
calculate a new slope and offset, write the current time to the last user calibration time register, and
set the next user calibration time register to zero (disabled). If the concentrations at 100% and 0%
saturation are equal, the probe will return an exception response with code 0x97 (invalid calibration)
and not attempt to compute a new slope and offset due to possible division by zero. If the slope does
not calculate between 0.85 and 1.20 inclusive, or if the offset does not calculate between -0.2 and
+0.2 inclusive, then the probe will return an exception response with code 0x97 (invalid calibration).
The slope and offset will be available for read but will not be committed to flash.
11. Optional: Read the last user calibration time register, add the next calibration interval, and write the
result to the next user calibration time register.
12. Write the Calibration Mode Off command (0xE002) to the sensor command register to place the
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