Hi thanks. What I'm doing is making a water meter for my motor home that reads the fresh and grey water using ultrasonic sensors I have a working prototype using two hc-sr04 I need to replace them with waterproof versions as water contact with the sensors is unavoidable as the vehicle moves. I was hoping the replacement ( linked above ) would be a direct replacement ( no such luck ). When I hooked them up I got no reading at all and have no idea where to go to get them to work. I purchased the plwm version. Hope that cover s it. Thanks in advance for any input.