Its not clear from the datasheet how slowly you can run the sensor - its designed to
shiftout samples at 1MHz or so, but there doesnt seem to be an indication of how
slowly it will work.
As configured the Arduino handles about 10k samples per second, note. The ADC can be
pushed faster, and for this device it looks like using the internal 1.1V reference is a good
move as the output seems to be 0 .. 0.8V range.