Calibrating the humidity sensor on the OpenHumidor board - sharst/OpenHumidor GitHub Wiki

If you have built an OpenHumidor Board yourself, you will notice that the humidity readings can be far off initially. Not to worry! OpenHumidor v0.5 now features a fairly automatic calibration mechanism, that will get your readings on the right track again.

Step 1: What you need

• A jar that you can close air-tight
• A teaspoon of ordinary salt
• A shot glass
• an OpenHumidor v0.5 board to be calibrated.

Step 2: Set up the environment

Put the salt in the shot glass and mix in some water drop by drop until you get a thick paste. Put the shotglass into the jar.

Step 3: Enter calibration mode

Make sure that the OpenHumidor board is switched off. Use a jumper to bridge the calibration connector (see image below). Put the OpenHumidor board next to the shot glass into the jar, switch it on and seal the jar airtight. Keep the jar in a spot at room temperature and away from direct sunlight.

Step 4: Wait and watch

The salt paste will create an air moisture of exactly 70% within the jar. When the OpenHumidor board senses that the surrounding humidity is constant, it assumes that a state of 70% is reached. It then remembers the error of the last reading as an offset for all readings in the future. Once the humidity has stabilized, the blue LED will start flashing.

Step 5: Exit calibration mode

Congratulations, you sensor board is now calibrated. Open the jar, switch off the sensor board, take off the jumper and start using your newly calibrated sensor!