Jester
Full Member level 6

I'm troubleshooting a new design and don't understand some of the results. Perhaps someone has some insight?
This is the circuit:

A short burst (3-4 cycles) of 40kHz is applied to the transducer via U4, the mux is then switched to listen mode.

The transducer rings for about 600uS after the burst completes (as expected and seems reasonable)
With nothing for the burst to reflect off, I would expect the receive signal to remain quiet after the initial decay, however a signal is detected about 1.4ms after the initial pulse, I have no idea why this is happening.
Any ideas?
This is the circuit:

A short burst (3-4 cycles) of 40kHz is applied to the transducer via U4, the mux is then switched to listen mode.

The transducer rings for about 600uS after the burst completes (as expected and seems reasonable)
With nothing for the burst to reflect off, I would expect the receive signal to remain quiet after the initial decay, however a signal is detected about 1.4ms after the initial pulse, I have no idea why this is happening.
Any ideas?