A basic ultrasonic level sensor measures liquid levels using the principle of ultrasonic sound waves. It consists of a transducer that emits ultrasonic waves and a receiver that detects the reflected waves. The sensor operates on the time-of-flight principle, which involves measuring the time taken for the ultrasonic signal to travel to the liquid surface and back to the sensor.
Here's a step-by-step explanation of how a basic ultrasonic level sensor works:
Emission of Ultrasonic Waves: The sensor's transducer emits a burst of ultrasonic sound waves at a specific frequency, usually in the range of 20 kHz to 200 kHz. The transducer can be either piezoelectric or magnetostrictive, depending on the design of the sensor.
Reflection from Liquid Surface: The ultrasonic waves travel through the air above the liquid until they encounter the liquid's surface. At this boundary between the air and liquid, a portion of the sound wave is reflected back towards the sensor, while the rest continues to propagate through the liquid.
Receiving Reflected Waves: The receiver in the sensor picks up the reflected ultrasonic waves. The sensor's electronics measure the time it took for the emitted wave to return to the sensor after being reflected by the liquid surface.
Calculating Distance: Using the known speed of sound in air (approximately 343 meters per second at room temperature) and the time it took for the wave to travel to the liquid surface and back, the sensor calculates the round-trip distance from the sensor to the liquid surface.
Level Measurement: Since the sensor knows the distance from the sensor to the liquid surface, it can calculate the liquid level. This measurement is typically provided as an output in various units, such as inches, centimeters, or as a percentage of the total tank height.
Compensation: Advanced ultrasonic level sensors may incorporate compensation techniques to account for factors that can affect the speed of sound in air, such as temperature, humidity, and air pressure. This helps ensure accurate level measurements even in changing environmental conditions.
Ultrasonic level sensors are commonly used in industrial applications to monitor liquid levels in tanks, reservoirs, and other containers. They are popular due to their non-contact nature, high accuracy, and ability to work with a wide range of liquids, including water, chemicals, and oils.