Calibrating Cozir Sensor Board

Most sensor instruments need calibration of their measurements from time to time. Here are the steps to set up / calibrate sensor boards:

(If you cannot put it outside, then you can still do all other steps to see if it is responding normally. This program both displays and calibrates.)

 STEP 1: Download Code

You need to download the program found at this MakeCode link (by pressing the download button below the program): http://bit.ly/admin-cozir ( long URL is here: https://makecode.microbit.org/46896-04233-14422-39275 ). 

The program file has the following:

• Will scroll data readings by pushing Button A to change mode from CO₂ / Temp / RH

• A “set up COZIR” code – pushing Button A + B and receiving an “x” on the matrix display - that should have been done initially at the factory but might not have been and could be why you have a “dead” sensor.

• A “calibrate COZIR” code – pushing Button B and receiving and “+” on the matrix display - that resets the PPM level to 400 – equivalent to Earth (outside).

STEP 2: Flash micro:bit

• Transfer the uploaded program (from the above URL link) to your micro:bit. 

STEP 3: Physical Connections

Using the alligator clips, connect the COZIR sensor board to the micro:bit, as seen in image below:

STEP 4: Calibration

• With the micro:bit still plugged into your computer AND attached to the sensor board – set them outside for about 3 minutes (3 to 5 minutes should suffice to clear out the detection chamber).

o NOTE: We will use this set up – LAPTOP USB -> micro:bit <- sensor array board to ensure the COZIR is receiving enough power for these set up functions.

• Once the micro:bit / sensor array has been sitting outside for 3 – 5 minutes, we will then use the “set up COZIR” function to ensure it is ready to go - press both buttons A+B at the same time. An “x” will appear to confirm the function is sent. 

• Press Button B until the “+” sign appears - this will “calibrate COZIR” and reset the base level PPM reading to 400 (Earth)

STEP 5: Final Check

• Press Button A until you get the ppm reading which should be around the 400 ppm value.

ALTERNATE 24 HOUR PASSIVE CALIBRATION METHOD

• Hook up a good 9v Battery to the Cozir Sensor board. Do not attach the micro:bit. Leave the battery connected without interruption for the duration of this method.
• Connect a NEW 9V battery to the battery cable and connect it to the 9V plug on the COZIR sensor board. The light on the "Monk Makes" logo in the corner should be light up to confirm the sensor is powered. Leave the battery connected without interruption for the duration of this method (24 hours). You do not need to attach the micro:bit.
• Take the sensor board with the battery attached to an area of good clean fresh air (assuming it is Zero to plus 20 Celcius and most likely @400 PPM CO2, as is most fresh air).
• With the battery attached and power confirmed, take the sensor board to an outside location or place it as near to an open window source as possible where it can acquire a fresh air sampling. The approximate temperature of this location should not be lower than zero and not in excess of +20 degrees Celsius. 
• Leave it in the fresh air for @ 5 mins or more and then return to a safe resting place and allow 24 hours to pass. It is important that the power to the COZIR is NOT interrupted during this 24 hour period.
• After 24 hrs, the COZIR will automatically reset to the lowest PPM sample as the base calibration point for 400 PPM.
•  Disconnect and using a micro:bit and program, test the COZIR to ensure that the values returned now appear within your expected values (e.g. compare fresh air with indoor air and samples with a few human breaths directly on the chamber).
• You can now connect the micro:bit with the Level 1 or Level 2 code program to the COZIR sensor with the alligator clips to test the COZIR to determine if the values now appear within your expected range. (e.g. compare fresh air with indoor air and samples with a few human breaths directly on the chamber).
• **IMPORTANT** with the micro:bit connected to the COZIR sensor, ONLY ONE POWER SOURCE should be used. Either the 9V battery attached via cable to the COZIR sensor OR the USB cord attached to your computer and the micro:bit's micro USB port. DOUBLE POWERING may cause damage to the hardware.
• If you still have concerns, document your sampled values and the setting and procedure you used, and send to [email protected]