This is just a guess, but I think he wants to digitize the 50KHz signal a= nd do some processing on it. Unfortunately, the rule of thumb for signal= processing says that you need to digitize at least 2X your highest frequ= ency of interest (100K samples/sec). But if you are trying to do DSP on a= 50KHz signal you would need to digitize faster -- 3X or even 5X. The A/D= converter is not going to run at 250K samples/sec. --- you need an exter= nal chip to do that. But that's not a big deal: 12-bit 1MegaSamples/sec chips are readily available and are pretty cheap,= even. Roy J. Gromlich Jinx wrote : > > can i use PIC18F452/10bit ADC/ to detect 50Khz sound > > with sampling frequency 100kHz? >=20 > I think even under the best conditions that's pretty much on or > past the limit (according to Table 17.1 of the 18F452 manual) >=20 > If you're wanting to just detect the presence of 50kHz rather > than measure frequency, how about something like an LM567 > or a similar notch filter to produce a there/not there signal for > the PIC ? -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics