Hi,
I'm using an LED as a light sensor. It is shunted by 200k and buffered by a
voltage follower, then sampled by the MAX197 on the 7250. The follower has a 2k
pull down resistor since the op-amp can't sink enough current at outputs near
the 0V rail.
All other channels seem to sample correctly but don't sample this low. This one
seems to need double read on low voltages.
Subsequent samplings seem correct but after delay of about a minute the initial
reading is at or near zero.
$ ./adc_logger -c 4 3,0 && sleep 15 && ./adc_logger -c 4 3,0
# ch3
0.071
0.067
0.071
0.067
# ch3
0.068
0.070
0.000
0.070
$ ./adc_logger -c 4 3,0 && sleep 60 && ./adc_logger -c 4 3,0
# ch3
0.072
0.070
0.071
0.071
# ch3
0.002
0.071
0.072
0.076
Testing the input to the follower shows the expected final value and is
constant.
I'm having a bit of difficulty seeing what may be happening, any ideas?
TIA.
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