Modern Device/Liquidware AMBI light sensor calibration problem

Using Arduino Sensors
10

What is the HiZ?

Oh, the autosense R/VDC/VAC function defaults to Lo Z, so you can check VDC/VAC
with Hi Z like a regular DMM in circuits like this where it might drag it down.

Paul from Modern Device got back with the below:

Problems trying to use your AMBI light sensor. It sounds great from
the description, but I don't see many examples using it successfully
because of the log conversion needed.

Most people don't bother converting to LUX and just use the output -
which unlike everything else on the market - has an intuitive
relationship to the way people see light.

Yes, that is simplest, but my application is a logging light sensor for PV panel placement,
so I need to actually calibrate it against my old Gossen LunaPro's EV reading, and not just
"bright" and "dim" like any photocell can do. I'm thinking now I should have gotten the TSL230R
and counted frequency but the AMBI looked like it could be calibrated.

AMBI voltage=4 Current=0.02 Light=1.05
AMBI voltage=15 Current=0.07 Light=1.18
AMBI voltage=12 Current=0.06 Light=1.14

I believe what you are seeing here is the sine wave inherent in your
"well-lit workbench" If you have fluorescent lighting it's really
noticeable and even with incandescent lighting there is a really
definite sine wave riding on the "average" value. We just can't see it
because our eyes are so slow.

Good point, didn't think of the effect of flicker on a fast sensor.
Probably ought to try it outside.

But I do agree those raw readings are too low for a well-lit bench -
they should be in 300 to 500 range. Let me know what your results are at
5V - maybe you need a new sensor.

Here's the cure:

long total = 0;
start = micros();
int i = 0;
while(micros() - start < 16666){ // if you're in Europe please use 20000
total += analogRead(ambipin);
i++;
}

average = total / i; // make sure you're not overrunning the long
variable too - you might need a small delay in the loop

report back your results and see if that hasn't fixed the "flicker"
also drag the sensor out in the sun and see if the flicker goes away.

Other ideas:
The datasheet recommends a 47 or 50K resistor - I'm using 100K for a
little more sensitivity on the low end - it will saturate on the high
end. (daylight) For outdoor use just use a 100K resistor in parallel
with the output for a total of 50K

Thanks, will try those things.

It's a high impedance circuit so make sure you have cleaned the pins
with isopropyl alcohol after you soldered them on.

I haven't used the sensor much at 3.3V so let me know your results. It
may saturate a lower voltage since your supply is lower.