A basic ultrasonic level sensor measures liquid levels using sound waves. It operates on the principle of ultrasonic ranging, which involves sending an ultrasonic pulse (high-frequency sound wave) towards the liquid surface and measuring the time it takes for the pulse to travel to the surface, reflect back, and return to the sensor.
Here's how the process works:
Emission of Ultrasonic Pulse: The ultrasonic level sensor emits a short burst of high-frequency sound waves (typically in the range of 20 kHz to 200 kHz) from its transducer, which is the part of the sensor responsible for both emitting and receiving sound waves.
Reflection from Liquid Surface: The emitted sound waves travel through the air until they encounter the liquid's surface. At the liquid-air interface, a portion of the sound waves is reflected back towards the sensor while the rest continues to travel into the liquid.
Receiving Reflected Signal: The transducer of the ultrasonic level sensor also acts as a receiver. It detects the reflected sound waves that bounce back from the liquid surface.
Time Measurement: The sensor measures the time it takes for the emitted sound pulse to travel to the liquid surface and back to the sensor. This time duration is commonly referred to as "time of flight."
Calculating Distance: Since the speed of sound in air is relatively constant, and the time of flight is known, the sensor can calculate the distance between the sensor and the liquid surface using the formula: Distance = (Speed of Sound × Time of Flight) / 2
Level Calculation: With the distance between the sensor and the liquid surface determined, the sensor can now calculate the liquid level. This can be done by subtracting the distance measured from the sensor's reference point (usually the sensor's mounting position) to the liquid surface.
Output: The liquid level information is then converted into an appropriate output signal (e.g., analog voltage, current, digital signal) that can be used by control systems, displays, or other monitoring devices.
Ultrasonic level sensors are widely used in various industries to measure liquid levels in tanks, containers, and other vessels. They are popular due to their non-contact nature, accuracy, and ability to work with a wide range of liquids, making them suitable for both clean and harsh environments. However, it's important to note that some factors like temperature, air humidity, and liquid properties can affect the accuracy and performance of the sensor, so proper calibration and environmental considerations are essential for optimal results.