The use of ultrasound technique to obtain the liquid film thickness was investigated. Ultrasound imaging is a technique that uses high frequency sound waves to produce precise images of structures. Ultrasound imaging is based on the same principle as SONAR (Sound Navigation and Ranging) during which a transducer capable of generating and receiving high frequency sound waves, sends pulses of sound waves into the interrogation area and the sound reflected back (echo) form any interface (such as water air interface) within the interrogation plane is obtained by the transducer. The time taken for the sound wave to travel from the transducer surface to the water air interface is obtained from the delay of the echo signal with regard to the transmitted signal; this time is used to compute the distance of the interface knowing the velocity of sound in medium. An experiment was set up to measure the depth of water in a container using ultrasound technique. A-mode (amplitude-mode) scanning was used where a pulsed ultrasound wave is directed into the interrogation region and echoes generated at various interfaces are detected. It is observed that levels as low as 0.55 mm were measured.

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