I've been working on a project where I need to measure the water level within a small underground compartment which measures 70x60x40cm (hxwxd).
I'm currently using a Hc-sr04, I'm getting good readings against a wall but when I put the device into the small compartment I get completely incorrect readings when at the top of the compartment. Instead of reading say 70cm it says 1cm. When I move the device down the height of the compartment to 30cm I start to get correct readings. I'm guessing I'm getting echo's due to the small area, is this correct and if so is there anything I can do to solve this? Appreciate your help.