I don't think you need a loop here. It is not clear exactly what you are trying to accomplish. I can't tell if you want to update the actual values in the db or just change how it is displayed. I'm thinking the latter.
So to display this you would do this:
SELECT CASE WHEN adc2 = 0 THEN 0
ELSE 10.3 * 0.00001 * adc0 - 0.334 END AS adc2