[SOLVED] PIC 18f452 Analog to Digital sampling time

Hello
what is the sampling time(A/D) between each sampling in PIC microcontroller such as PIC18f452?

Depends how you configure it and what your clock speed is.

There is acquisition time and conversion time. You you need to account for acquisition time when changing the active ADC channel. Once that time has been allowed, then you are working with conversion time.

The acquisition time depends on source and reference resistances and temperature, the formulae are on page 185 of the datasheet. For a 2.5KΩ source resistance and internal ref, it works out around 10µs for the hold capacitor to be charged and everything to be ready.

Then...

A 10-bit conversion requires 12 T_AD cycles. T_AD is set in software, to one of 2,4,8,16,32 or 64 x T_OSC or the internal AD RC oscillator. Also, the fastest you can allow T_AD to be is 1.6µs. That alone sets a minimum conversion time of 12x1.6 = 19.2µs. T_AD is set according to your clock; for example 10MHz with 16xT_OSC gives exactly 1.6µs for T_AD.

Doing something with the samples will take more time of course.