hi guys,
thanks again for your replays,
as Roff did say, the use of a drop sensor is appropriate,
by luck
, I've found a schematic of a drop sensor used for a blood pump from early 90's,
it is almost what I'm looking for, I named (in red)the OP Amp in the schematic (as my understanding of the synoptic), and I'ill be pleased if someone verify it with me
,
some questions about the schematic came into my mind:
-what is the role of the rectifier.
-why the Pass band filter have two stages ? (is it possible to replace it with just one ?)
-why do the comparator compare the output signal with 3.4V
-I simulate the first stage of the pass band filter using ISIS Vsm and the frequency graph response shown a high attenuation (-60Db), what is the reason ?
-what are the parts of the schematic that we can replace with the PIC.
thanks in advance.