A human can hear the sound of a maximum 20 kHz frequency. Ultrasonic is the sound that is above the human hearing range, with the frequencies of above 20 kHz. And the normal frequency range that is used for ultrasonic level measurements is 40-200 kHz. Few animals such as the bats and frogs use the ultrasonic sound to communicate with each other. Bat use the sound for navigation by emitting the high pitch sound of short wavelength to check the distance of the object on their way by listening to the bounce-back of the ultrasonic waves.
Uses of ultrasonic waves – it is used to measure the level of liquids and solid objects, especially that is used in the industries. The level of ultrasonic measurement is through the contactless principle and the most suitable for hot, corrosive and boiling liquids used in the industrial equipment. Ultrasonic level measurement is used in the fishing to find the right position of the fish in the ocean, locate the submarines and position of the scuba diver in the sea.
Principle of Ultrasonic measurement level
The principle of detecting the object is the same as the radar, by pulse signalling the target object, the reflection by the object and the echo that the sender receives. Time travelled by the ultrasonic pulse is calculated to find the distance of the object. This is similar to the bat that uses the ultrasonic sound for navigation.
The technical side of ultrasonic level transmitter
To find the level of liquid in a tank is measured using the ultrasonic level transmitter is fixed at the top of a tank half-filled with liquid. The distance of the ultrasonic sensor from the liquid level is calculated from the ultrasonic pulse signals. Ultrasonic pulse signals are transmitted from the transmitter and reflected in the sensor.
The travel time of the ultrasonic pulse from the sensor to the liquid level and back is calculated to arrive at the right level of the liquid in the tank.
Level is = Speed of sound in air x Time delay / 2
But though the process sounds simpler, there are some technical difficulties which should be taken care to derive at the right reading –
- The velocity of the sound changes when there is change in air temperature. For this, the temperature sensor should be integrated to compensate for the velocity changes of sound due to temperature variation.
- The software of transmitted should be installed to identify the interference echoes could be produced from welded joints or edges. It helps in the suppression of interference echoes.
- Accuracy in the measurement is dependent on the calibration accuracy.
- There could be blocking distance developed due to transient characteristics of the sensor.
The ultrasonic level transmitter instruments work solely on the sensor that translates the electric energy into ultrasound waves. Coltraco Ultrasonics design ultrasonic products across level, seal, thickness, flow & acoustics & to improve safety for your people, assets & infrastructure on land & at sea. We manufacture ultrasonic technology in UK that will save you time, cost & risk. Contact us to know more about our ultrasonic testing products.