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I am developing a circuit for calculation of time spent for the wave to travel from one end of sample to another. The length of sample varies from 0.5 cm to 10 cm.
I have generated sinewave and I want to determine the instance the wave hits the sample and the instance the wave gets out of it. Once, i determine the first instance, i will start the timer and stop it once i determine the next instance. Transducer is used to convert the electrical signal to ultrasonic signal which hits the sample and viceversa.
I am developing this circuit using AVR microcontroller. I found that the inbuilt Timer clock frequency doesnot exceed 8KHz. But I want to operate my timers are higher frequencies around 4 Mhz. Please suggest me inputs.