The UV sensor that i bought is not working correctly. It gives wrong output values.
It does not give linear output. It has a very strange linearity until 0.3-0.4 Volts and then it gives the maximum value which is 3.3V.
I am comparing with two other existing UV sensors and until 3 UV index, they have quite similar values but after that the grove uv sensor’s output goes to max value.
One day with about 7 UVI, i got at the terace and i hold the grove sensor and the two other uv sensors all connecting to 3 voltmeters (all right pararel between them) in my hand.
Then i was comparing values at:
a) right straight to sun
b) moving to left and to right (i mean more left and then more right that straight to sun).
Well, the grove board at dark (no light) gave 0.27 Volts (the other boards gave zero). When the other boards gave 0.1 Volts (which is about 1 UVI) the grove board gave 0.4 Volts. And when the other boards gave 0.45 Volts or more (which is about 5 UVI) the grove goes directly to 3.3V (the maximum value of power supply) which is not correct.
What i noticed at the schematics is that the feedback resistor that controls the photodiode’s gain is 10 MΩ and the there is an other extra 6.1 gain.
But in the internet i see that everyone is using a 1 MΩ resistor (which means 10 times less gain).
So, is it a wrong design or just a faulty sensor?