Hi Mahmood,

Sorry to hear about your car. I reckon the forklift is fine.

A colleague and I played with some ultrasonic transducers about a year ago in hopes of making a single transducer, fixed frequency, liquid level sensor. Without going into details of the setup and our performance goals, it'll suffice to say we were bedviled by two difficulties - (1) multipath, which caused variation of indicated level and (2) decay (or 'ring down') of the transmitted signal, which determines the minimum distance of the target object to the transducer.

We were able to greatly mitigate the decay problem by reverse driving the sensor, but reliability of the reverse drive technique depended on initiating the a reverse drive pulse at the proper phase during the ring down. Having reduced the duration of ring down, we were able to reconnect (via semiconductor switches) the transducer from the drive circuit to a receiving circuit and pick up an echo reflected from the target object.

We could not solve the multipath problem easily and economically, so we went in another direction to determine liquid level.

Good Luck,

Bruce