PGA460-Q1: PGA460 TDC1000

Hi Alex,

Unfortunately, it is very difficult to use ultrasound to penetrate through a metal tank, have enough energy to then propagate through air, reflect from a liquid surface, and then reverse the process back through air final through the metal cylinder.

The issue stems from the concept of acoustic impedance mismatch. Metal and air are largely mismatched, thus the bulk of energy will reflect rather than penetrate through the initial transmit medium. More specifically, the bulk of the energy will be reflected at the interior layer of the metal tank rather than transmit into the tank during the initial burst.

That's not to say it is impossible. With proper coupling of the transducer to the tanks exterior (i.e. coupling agent such as specialized gel or glue), and depending on the tank's thickness , it may be possible to detect returning echoes. This will likely require using the maximum allowable transmit energy (Vpp rating) allowable by the transducer to ensure the sound pressure level saturates.

We have not experiment with detection through metal tanks/cylinders, so we are unable to provide specific transducer/frequency recommendations. However, I would consider using a high-frequency air-coupled transducer (180k-480kHz), as high-frequency transducers are more suitable for ultrasound propagation through denser materials. See the Air-Coupled Ultrasonic Transducers & Transformers Listing at e2e.ti.com/.../620399 for a complete listing of high-freq transducers and transformers.

Thnaks Akeem,

i also think about acoustic impedance (resonance) but need measure frequence ranges and depends from ballon configuration.
I'll other transuders (180-400 kHz) with high power.