In-situ RDO PRO-X, Operator'S Manual, Page: 25 / 29

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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 sensor in normal
operation. If the calibration mode is turned off without a calibration update command, or the calibration command
returned an exception, the previous calibration shall be restored.
13. Optional: If you saved the temperature and saturation parameter units at the start of the process, write the original
values back.
14. Optional: If you saved the Sensor Data Cache Timeout register 9463 at the start of the process, write the original
value back.