A02YYUW False Echo / Ghost Reading Inside 89mm PVC Stilling Well

Hi everyone,

 

First time here.

 

I'm working on a water tank monitoring project using the A02YYUW waterproof ultrasonic sensor. The sensor is mounted at the top of a vertical PVC stilling well with outer diameter is around 89mm (3.5"). 

 

The system is working, but I'm observing a persistent false echo (ghost reading) at around 300mm (~1 foot). The value is stuck there. if I take the sensor out of the stilling pipe and tank, its working. Guess acoustics echo because of wide angle.

 

 

 

A few details:

 

 - Stilling well inner diameter: approx. 87mm - Sensor mounted flush at the top of the pipe - Pipe length: 1.5meter - Ghost reading stuck at: approx. 300mm

 

What is the minimum(optimal) recommended pipe inner diameter?

 

Note: If I place the sensor without stilling pipe, the value is still stuck at around 1.5 or 1.8 feet.

 

I would appreciate any guidance from anyone who has used the A02YYUW in a similar water-level application.

 

Thank you.