Ultrasonic Level Sensors

"Ultrasonic level measurement is used for short and long range measurement. It is a contact less technology used in numerous industrial areas to monitor the level of liquids, solids and slurries. Sound waves which have frequency above 20,000 Hz are known as ultrasounds. Ultrasonic sensors used ultrasounds to measure and calculate the distance from the sensor to a specified object.



Ultrasonic sensors use electrical energy and a ceramic transducer to emit and receive mechanical energy in the form of sound waves. This ceramic transducer vibrates when electrical energy is applied to it. The vibrations compress and expand air molecules in waves from the sensor face to a target object. A transducer transmits as well as receives sound. The ultrasonic sensor will measure distance by emitting a sound wave and then receiving for a set period of time, allowing for the return echo of the sound wave bouncing off the target, before transmitting again. Sound waves are basically pressure waves which can travel through solids, liquids and gases. These can also be used in industrial applications to measure distance or detect the presence or absence of targets.



Ultrasonic level sensors are used in lieu of optical sensors. These have an advantage over their optical counterparts when it comes to clear object sensing, liquid level or highly reflective or metallic surfaces. These also function well in wet environments where an optical beam will get refracted off the water droplets. These advantages make them suitable for some specific applications where optical sensors can't be used because of the above mentioned limitations.



Sound has a much lesser speed than light. Since the ultrasonics are essentially sound waves and optical sensors use light, the former are much slower than the latter when it comes to raw speed. Among the other disadvantages is the fact that the ultrasonics is susceptible to temperature fluctuations and wind. Along with this, they have a slower response time and a bigger spot size than optical sensors. Any acoustic noise having the same frequency as that of the ultrasonic sensor may interfere with the sensor's output. This includes high pitched noises, noise produced by relief valves, noise produced by compressed air release or sound produced by pneumatic devices. Even when two ultrasonic sensors working at the same frequency are operating in the close proximity of each other, acoustical crosstalk is possible which interferes with the readings of the sensor.



Ultrasonic sensors should not be operated without warming them up first. When they are first powered up, their components heat up and also warm up the surrounding space and components. This variation in temperature from a cold start to the operating temperature is called ""Warm-up-drift"". Untill all components have stabilized at the correct operating temperature; the accuracy of the measurements may get affected.



Overall, ultrasonic sensors when operated properly can serve many important purposes and work in different capacities. They can be used in conditions where optical sensors fail."



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