TolpuddleSartre:
The microcontroller has very little to do with the sensitivity (assuming that's what you meant by "uc").
The Tx is usually driven by a MAX232 or similar, and the Rx is amplified by an op-amp.If your transducers don't match the originals, you've got a problem on your hands.
hmmm. well i must have done something wrong when i bought the transducers. could you perhaps point me to a set of waterproof transducers that might work with this hc sr04 board. or perhaps maybe a uc that supports dual transducers like the hc sr04? i think that maybe this uc dont have enough power or something on this board is not in specs for these transducers i bought. . im not sure i think maybe since these transducers are enclosed in a metal case that it may need more power to drive them. i know the are both 40khz sensors