The LTR390 breakout board (ID 4831) provides software-selectable options for gain and data resolution. The sample code provided for the LTR390 UV and ambient light sensors chooses gain 3 and 16-bit resolution. Can someone tell me how these choices are made? Will either the ambient light or UV sensors "saturate" in bright outdoor sunlight? If so, would choosing a lower gain -- 1 instead of 3 -- prevent this from happening? What's the impact of choosing a higher or lower data A/D resolution?
What's the meaning of the ltr.setThresholds(100, 1000); statement in the sample code?
Any help will be greatly appreciated. Thanks!
choosing LTR390 options
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- adafruit_support_mike
- Posts: 67485
- Joined: Thu Feb 11, 2010 2:51 pm
Re: choosing LTR390 options
You choose the values that give appropriate readings for the conditions in the operating environment.earthres wrote:Can someone tell me how these choices are made?
They can. That's why you choose different gain and resolution options.earthres wrote:Will either the ambient light or UV sensors "saturate" in bright outdoor sunlight?
It could, yes.earthres wrote:If so, would choosing a lower gain -- 1 instead of 3 -- prevent this from happening?
In most cases it's a question of speed. Higher resolution usually requires a longer sampling time.earthres wrote:What's the impact of choosing a higher or lower data A/D resolution?
The LTR390 can generate interrupts when the readings go outside a specified range of values. Those are the ones we chose for the demo.earthres wrote:What's the meaning of the ltr.setThresholds(100, 1000); statement in the sample code?
- earthres
- Posts: 232
- Joined: Fri May 28, 2021 10:48 am
Re: choosing LTR390 options
Thanks, Mike. Does anybody out there have experience with using the LTR390 for measurements outdoors? If the ambient light sensor is some kind of lux sensor, it may saturate in full sunlight, which can be 100,000 lux or even greater. Most inexpensive lux sensors saturate well below that level. Note however that, with appropriate gain settings, Adafruit's VEML7700 is alleged to be good up to "about 120 klux."
- adafruit_support_mike
- Posts: 67485
- Joined: Thu Feb 11, 2010 2:51 pm
Re: choosing LTR390 options
I'm afraid we don't have any specific information. As with most sensors, you'll need to do some testing in the operating environment to characterize things and work out the set of sensors and techniques that give you the kind of measurements you want.
Please be positive and constructive with your questions and comments.