- Thu Nov 18, 2010 4:27 pm
#113869
Basically measure the voltage divider, it should be 1/2 the battery voltage. If its not then the AD input is loading down the divider too much and you'll need to decrease the resistor values.
Is your supply 5V or 3.3? If 3.3, then those analog switches don't like to be pulled above the supply.
If it is 3.3V, divide by 3, with 20M and 10M.
With resistances that high you're starting to get into the realm of very high impedance circuits. By the time you get to 100M, your circuit turns from being something useful to being an antenna picking up any stray signals. Also at those levels, just touching the resistors will leave enough perspiration to affect the values.
Is your supply 5V or 3.3? If 3.3, then those analog switches don't like to be pulled above the supply.
If it is 3.3V, divide by 3, with 20M and 10M.
With resistances that high you're starting to get into the realm of very high impedance circuits. By the time you get to 100M, your circuit turns from being something useful to being an antenna picking up any stray signals. Also at those levels, just touching the resistors will leave enough perspiration to affect the values.
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