A basic ultrasonic level sensor measures liquid levels by using sound waves to determine the distance from the sensor to the liquid surface. It operates on the principle of sending an ultrasonic pulse from the sensor and measuring the time it takes for the pulse to travel to the liquid surface, reflect back, and return to the sensor. Based on this time measurement, the sensor calculates the distance to the liquid surface, which, in turn, indicates the level of the liquid in the container.
Here's a step-by-step explanation of how the process works:
Emission of Ultrasonic Pulse: The ultrasonic level sensor contains a piezoelectric transducer that generates an ultrasonic sound wave. When triggered, this transducer emits a high-frequency sound pulse, typically in the ultrasonic range (above 20 kHz), towards the liquid surface.
Traveling to Liquid Surface: The ultrasonic sound wave travels through the air from the sensor towards the liquid surface in the container.
Reflection from Liquid Surface: Once the sound wave reaches the liquid surface, a portion of it gets reflected back due to the difference in acoustic impedance between air and the liquid.
Reception of Reflected Pulse: The sensor's transducer also acts as a receiver. It picks up the reflected sound wave (echo) that returned from the liquid surface.
Time Measurement: The sensor measures the time it took for the ultrasonic pulse to travel from the sensor, reach the liquid surface, and return as an echo. This time measurement is typically very short, often in the range of microseconds.
Distance Calculation: Using the speed of sound in air (approximately 343 meters per second at room temperature), the sensor calculates the distance to the liquid surface by considering the time taken for the round-trip of the ultrasonic pulse.
Liquid Level Determination: With the distance to the liquid surface known, the sensor can determine the liquid level in the container. The liquid level is often displayed on a screen or transmitted to a control system for further processing and monitoring.
It's worth noting that environmental factors like temperature and humidity can affect the speed of sound in air, so some ultrasonic level sensors might have compensation algorithms to account for these variations and provide more accurate readings. Additionally, the accuracy of ultrasonic level sensors can be influenced by the properties of the liquid being measured, container design, and potential obstructions or disturbances in the measurement path. However, they remain popular due to their simplicity, non-contact measurement, and versatility for a wide range of liquid level applications.