Sorry, yet ANOTHER mod question

[andywpg]

What kind of voltage divider you are using?
If you try to get full 0-5V scale with 0-15V input, then you should use 1:3 ratio (e.g. 22kOhm and 11kOhm resistors) to get best measurement accuracy.

With this divider 15V -> 5V (and 0V -> 0V) at ADC input pin, ADC should show 255 (8bit) or 4095 (12bit).

I'm using a 10K and a 3.3K and my ADCbits is set to 10. Here's the ADC setup (maybe I'm doing something wrong there)

DEFINE ADC_BITS 10 ' Set number of bits in result
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS
ADCON0 = %11000000 ' Set ADC_CLOCK to Frc, 
ADCON1 = %10000000 ' Right-Justify result in ADRESH:ADRESL registers, use Vss and Vdd as voltage refernces

[andywpg]

BTW, I should mention that its a 16F886

[Gusse]

Take a look to Voltage Divider Example.
There is everything you need.

10k and 3k3 doesn't give you 1:3 divider. Resistor ratio in your case should be 1:2 (e.g 11k and 22k).
Link above explain also divider math to calculate right values.

EDIT: Earlier post 12bit (4095) should have been 10bit (1023). My misstake!

[andywpg]

Take a look to Voltage Divider Example.
There is everything you need.

Problem solved! When I use the example code and plug in my actual resistor values, I get a reading that is within .1V of the actual. MORE than adequate for what I need. I only wanted it because the smoker controller could be running off battery - and I want to be able to shut it down and generate an alarm if the voltage reaches 10.5V. The user can also press a button while in auto mode to see the current voltage. A tenth of a volt out is NOTHING.

Thanks!

Andy