A basic ultrasonic level sensor measures liquid levels using ultrasonic sound waves. It operates on the principle of transmitting and receiving sound waves to determine the distance between the sensor and the liquid surface. Here's a step-by-step explanation of how it works:
Transmitter: The ultrasonic level sensor has a transmitter that emits a high-frequency sound wave (typically in the ultrasonic range, above 20 kHz). This sound wave is directed towards the liquid surface.
Sound wave propagation: The emitted sound wave travels through the air from the transmitter towards the liquid surface.
Liquid surface reflection: When the sound wave reaches the liquid surface, it gets partially reflected due to the difference in acoustic impedance between the air and the liquid. The acoustic impedance is the product of the density and the speed of sound in a medium. The density of air and liquid is significantly different, causing reflection.
Receiver: The sensor also has a receiver located near the transmitter. It detects the reflected sound wave that bounces back from the liquid surface.
Time-of-flight calculation: The sensor measures the time it takes for the sound wave to travel from the transmitter, reflect off the liquid surface, and return to the receiver. This time interval is known as the "time of flight."
Distance calculation: Using the speed of sound in air and the measured time of flight, the sensor calculates the distance between the sensor and the liquid surface. The formula used is:
Distance = (Speed of sound in air * Time of flight) / 2
Since the sound wave travels to the liquid surface and back, the distance is halved to get the actual level.
Liquid level determination: With the distance measured, the sensor now knows how far the liquid surface is from the sensor. By subtracting this distance from the total height of the container or vessel, the sensor can determine the liquid level.
Output and calibration: The sensor may provide a digital or analog output representing the liquid level. Depending on the specific model and application, additional calibration and compensation may be applied to improve accuracy and account for factors like temperature, pressure, and container shape.
Ultrasonic level sensors are commonly used in various industries to measure liquid levels in tanks, reservoirs, and other containers. They are popular due to their non-contact nature, which means they do not come into direct contact with the liquid, making them suitable for measuring corrosive or hazardous substances.