I have no idea which transducer you have. Do yo understand that with 99.9% of transducers the head unit sends a huge 100vpp pulse at the design frequency of the transducer, perhaps about 10 cycles of 200KHz and then the head unit goes into the 'listen' mode and amplifies and displays the return echos. Normal transducers don't use steady voltage from a power supply and also don't use a steady tone from a signal generator. The transducer is simply the peizo ultrasonic resonant equivalent of a radar antenna and just like a radar antenna it produces no actual data. it simply emits and receives pulses of a certain frequency and duration.