Calibrating O2 Sensor

1. Replace port="COM8" with port number currently assigned to O2 Sensor in modbus.py.

2. Run pip3 install pymodbus, if necessary in terminal.

3. Run python3 modbus.py in the directory modbus.py is located.

4. Script should display Raw value: <RAW DEVICE CURRENT> mA, Mapped value: <O2 BASED ON CAL POINTS>%"

5. Perform a 3 point calibration as follows:

   • For 0% oxygen (percent_1), apply pure nitrogen gas to O2 sensor, note raw device current after it is stable.
   • For 10.475% oxygen (percent_2), apply a 50% nitrogren gas, 50% Air mixture to O2 sensor, note raw device current after it is stable.
   • For 20.95% oxygen (percent_3), apply 100% air to to O2 sensor, note raw device current after it is stable.

6. Replace current_1,current_2,current_3 repectfully with the values noted in previous step.

7. Verify Mapped Value is as expected for the 3 calibration gases.

8. If all is expected, inside config.json, update the current_1,current_2,current_3 fields in the O2_sensor_calibration object.