i am using PIC 16F877A for Peak Detection. the analog signal is applied at Pin RA0. the program has been written in C. for frequency upto 60-65 Hz, the peak is properly detected. but for frequencies below that, peak is not detected properly, instead the pin goes high well before the peak. Please help me with this problem.

 

This is what is happing your adc is taking a reading say every 10 cycles it rolled past

 

yes, it might be true but what is happening is that it is showing high very early almost near the start of the waveform. so what can be the reason for that???

 

It would be nice to see some code. Adc may not be what you really want
Capture/Compare/PWM CCP would work better

every falling edge
every rising edge

http://ww1.microchip.com/downloads/en/DeviceDoc/chapter 3.pdf

Read tip 6

 

i am using PIC 16F877A for Peak Detection. the analog signal is applied at Pin RA0. the program has been written in C. for frequency upto 60-65 Hz, the peak is properly detected. but for frequencies below that, peak is not detected properly, instead the pin goes high well before the peak. Please help me with this problem.

Have you got weak pull ups turned on ?
They should be off.

Are you applying for than 5 volts to the ADC ?
The PIC will start to play up if you go over 5 volts.