In-Situ RDO PRO-X Process Optical Dissolved Oxygen Sensor Manual - Manual (Page 25)

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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.