The most important part of calibration is watching the readings during the calibration process. It is easiest to calibrate the device in its default state (UART mode, with continuous readings enabled). Switching the device to I2C mode after calibration will not affect the stored calibration. If the device must be calibrated in I2C mode be sure to continuously request readings so you can see the output from the probe. In this tutorial, the calibration will be done in UART mode.
The Atlas dissolved oxygen circuit has a flexible calibration protocol, allowing fora single point or dual point (optional) calibration. Temperature, salinity and pressure compensation values have no effect on calibration. Do the calibration first and compensate for these parameters later.
Use a breadboard to mount the circuit and BNC connector. Wire the D.O circuit to the Arduino Uno as shown in the schematic above and connect the probe to the BNC connector.