4 digit auto-ranging frequency-meter.
Peter Gee email (remove spam text)
What would happen in the schematic shown if the input voltage when negative
with respect to the gnd of the PIC ?
my guess is that it wouldnt be good for the PIC.
in a similar project ( from memory), they use a coil, capacitor, signal
diodes, and a transistor to filter and switch the incoming frequency to make
it nicer for the PIC to count.
i built the project, and it seemed to give accurate results in comparison to
a bench frequency counter at a frequency of 40Mhz using a 10Mhz 16cf84. (i
used an fm RC transmitter to calibrate it) -- i don't have a frequency
generator higher than that so i can't test its high end response.
See also: www.piclist.com/techref/index.htm?key=digit+auto+ranging
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