I don't think there is a tuned circuit. The inductor seems to be used as a choke rather than being resonant. The comparator is just that, it can be adjusted to trigger on the edges of cycles from the transducer.
I don't think there is a tuned circuit. The inductor seems to be used as a choke rather than being resonant. The comparator is just that, it can be adjusted to trigger on the edges of cycles from the transducer.
The inductor has no capacitor across it so it is not resonant. Using an inductor as the load of an amplifier is one way of getting a high impedance for the AC signal while minimising the voltage drop to DC.
The comparator has the negative input set by the voltage across R6. The other input can be set by R10 to be some way above the voltage on the negative input. This allows the sensitivity to be set - the pulse on the positive input needs to be bigger than the voltage dropped across R10 to trigger the output.