Hi all,
I am trying to make a circuit that measures the frequency of a tiny 20nV AC signal (~4000Hz) generated by an inductor coil I will ultimately be bringing the signal into my PIC16F1713 (which has a Zero Crossover Detect (ZCD) module). There are many possible ways to go about this, so the ZCD may seem convenient but maybe there are better methods.
To use the ZCD at least, my method would be to chain op amps to give a combined gain of 50M to get the signal to 1Vpp. I could then reliably use the ZCD module to trigger an interrupt and count frequency. I worry though, the signal itself is from inductively picking up a resonators motion so I imagine the sine wave created will be distorted to some degree. I also imagine the large gain could make noise an issue. With these factors in consideration are there other methods that could work great with uV or mV level AC signals and therefore wouldn't require me to amplify the signal as greatly?
Just brainstorming, perhaps I could amplify to the minimum level for a comparator to work, then into the PIC? Or maybe directly into the ADC of the PIC? Any help is appreciated!
I am trying to make a circuit that measures the frequency of a tiny 20nV AC signal (~4000Hz) generated by an inductor coil I will ultimately be bringing the signal into my PIC16F1713 (which has a Zero Crossover Detect (ZCD) module). There are many possible ways to go about this, so the ZCD may seem convenient but maybe there are better methods.
To use the ZCD at least, my method would be to chain op amps to give a combined gain of 50M to get the signal to 1Vpp. I could then reliably use the ZCD module to trigger an interrupt and count frequency. I worry though, the signal itself is from inductively picking up a resonators motion so I imagine the sine wave created will be distorted to some degree. I also imagine the large gain could make noise an issue. With these factors in consideration are there other methods that could work great with uV or mV level AC signals and therefore wouldn't require me to amplify the signal as greatly?
Just brainstorming, perhaps I could amplify to the minimum level for a comparator to work, then into the PIC? Or maybe directly into the ADC of the PIC? Any help is appreciated!