VEML7700 multiple readings not equal

Using Arduino Sensors
1

Hello,
I am playing around with the VEML7700 to get the ambient light.
I have done 4 readings and consistently I get two different values.

Here are my settings and values:
Gain 1, IT 100ms -> 7351 counts * 0.0576 = 423 lx
Gain 2, IT 100ms -> 14706 counts * 0.0288 = 423 lx
Gain 1/4, IT 100ms -> 2249 counts * 0.2304 = 518 lx
Gain 1/8, IT 100ms -> 1123 counts * 0.4608 = 517 lx
Gain 1/8, IT 25ms -> 280 counts * 1.8432 = 516 lx

So I get basicly two different results, 423 lx and ~517 lx. The difference gets bigger the brighter the light. But allways the first two are the same and the last tree are the same.

What is going on here? any one have some tips?

Thanks
Best regards

2

There's a comment in the application note that gain factors 1 and 2 don't have the same linearity as the lower gains. This already might explain the results.

3

Thanks for the reply. I missed that.

So one should always use the smallest gain and longest integration time as possible I suppose?

4

Longer integration time normally gives higher accuracy - so yes, unless you have a reason to have a shorter time such as the need of taking more frequent readings.

Gain, check the datasheet. Usually that does not affect accuracy, it may increase resolution.

5