Arduino humidity sensors: testing and calibration

Three sensors have ability measuring 20-80% RH with accuracy +/-3%
SHT21 and DHT22 are sensors for measuring humidity and temperature.
BME280 is sensor from well-known maker Bosch, for measuring atmosphere pressure, humid and temperature.
This video will show test result of those 3 sensor to check which one is the best one. However, none of them are correctly. We need to calibrate it with simple things.
After make sensor correctly, then we can use it to measure humid and temperature of room, view via internet by Blynk software
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Code and circuit

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Other meaning project made by me:

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[matheussteinmetz]

Sensirium sensors are the best. SHT40 is the best you can buy

[sylvainmartin]

instead of using an offset to your measurement use the function map(value, fromLow, fromHigh, toLow, toHigh), it's a arduino built in function. If you had a low datapoint you could use it to calibrate linear data like temperature, humidity, pressure. the salt method is good for getting a high value, there are other salts you can use to get the low datapoint, like the damp rid stuff

[FOATE]

Very very good tip with the saturated NaCl that is the best tip I have ever had regarding humidity sensor calibration. Thank you very much for making this video!

[HeavyHeavyvich]

It was necessary to multiply, and not use addition. And, it is quite obvious that the correction coefficient will be nonlinear. You should find several points, and for each segment to calculate your correction factor.

[LarryKapp]

Thanks - I just put up three sensors outside and they are all different. Now I know how to calibrate.

[mariomoreno]

ry with water saturated in NaCl (100ml with 36 grs. of NaCl) mix and leave for stabilize, you shoud have a 45 HR between 20 and 60C degree. The problem sometimes is the temperature sensor and as HR is calculated from temperature, that could be the beginning of errors in HR values.

[RPUXO]

The DHT22 sensors I got all read grossly erroneous humidity values - either 1% or 100%.
The temp readings are OK though.
Has anyone else notice that ?
Is there any solution for those faulty DHT22s ?

[makers_lab]

The humidity sensors use capacitive sensing, so I wonder if the proximity of the devices to each other in the chamber would have an effect. Also, the BME280 is calibrated by the manufacturer and values baked into registers. I'm wondering if these factory calibration values were taken into account in the readings, or whether you used raw values.

[circle]

Wow, very nice, thorough work.
So, the hygrometers that people buy at local stores are garbage, and the readings people tell you that they get from them are probably wrong. That's not reassuring at all.

Thanks for this video.

[hamedvalizadeh-oebu]

So if you want to have more than one device of this project, you need to change your code for each of them. Imagine you produce it in mass amount. Is it logical to change your code for each one????

[vetrivelrajeswari]

Good very useful video.
Thank you.
Sorry sir. I am watched this video too late. (26.09.2022). INDIA .T.N.

[JavaMike]

Hi there... I really liked this video. I know its old, but I am trying this method with only BME280 but I get so many errors when trying to upload the code to a ESP32. If you could help, it would be great. I want to use the map function.

[thanh-gtpham]

It's really amazing! Thanks for your good work!

[mostafaal-hajee]

Why not create an educational course on this type of programming? It will be fun

[afiqharis]

may I know, what is the hypothesis of this project?

[aymenbousselmi]

Hi sir, i wanted to ask you if linear regression can improve the bme280, have you used for this sensor?

[mostafaal-hajee]

I am very interested in calibrating my temperature sensor, but I could not understand, it is difficult for me

[TheJaimecasado]

Hi, what will be the Python code for the double map funtion to make the correction. I'm new on this and kind of lost. Bests

[GeorgeJeffin]

Hey, i checked Sodium chloride but my humidity going above 80% why? both sensors showing the same

[genome]

can you also do this with aht10 thanks