Reading values greater than resolution from analog channel

[semiherakay]

I'am using 16F886. In my program, I'm trying to check 3 different analog channels continuesly. I'm also using timer1 interrupt with two different starting point successivly. First interrupt cycle ranges from 0,4 ms to 9,6 ms and successive interrupt cycle from 9,6 to 0,4 ms as you see I'm trying to generate a PWM signal with different duty in 50HZ to generate a voltage at different levels.

I'm trying to check voltage level from one of my analog channel. In low level voltage values (150V-200v)there is no problem with adc but when voltage level is getting bigger(>200v -300v) I'cant read correct values from adc. Returning values are greater than 1023 (16F886 has 10 bit resolution adc) in high voltage levels.

If you have any suggestion I'll be glad.

[Foppie]

I would say: look at your voltage divider.
What sort of hardware do you use to get these high voltages to the low voltages the PIC accepts?

If this PIC however supports high voltages (I'm unaware, but haven't worked with that PIC before) then have a look at the datasheet.

Jos