A basic ultrasonic level sensor measures liquid levels using sound waves. It emits ultrasonic pulses (high-frequency sound waves) from a transducer, which is a component of the sensor. These pulses travel through the air above the liquid and then reflect off the liquid's surface. The sensor then measures the time it takes for the reflected pulse to return to the transducer.
The principle behind this measurement is based on the speed of sound in the air. Since the speed of sound is constant, the sensor can calculate the distance between itself and the liquid's surface by multiplying the time taken for the pulse to travel to the liquid surface and back by the speed of sound in air, and then dividing by 2 (since the pulse travels to the surface and back).
Here's a step-by-step breakdown of how the process works:
Transmitting Pulse: The ultrasonic level sensor sends out a short burst of ultrasonic sound waves. These waves travel through the air and head towards the liquid's surface.
Reflection: When the ultrasonic waves reach the surface of the liquid, they encounter a change in density between the air and the liquid. This causes a portion of the sound waves to be reflected back towards the sensor.
Receiving Pulse: The sensor's transducer, which emits the ultrasonic waves, also functions as a receiver. It detects the reflected pulse that has bounced back from the liquid's surface.
Time Measurement: The sensor measures the time it takes for the ultrasonic pulse to travel to the liquid's surface and return. This time is typically very short, in the order of microseconds.
Calculating Distance: Using the known speed of sound in air (which is approximately 343 meters per second or 1125 feet per second at room temperature), the sensor calculates the distance between itself and the liquid's surface. This calculation is based on the formula: Distance = Speed of Sound × Time / 2.
Liquid Level Determination: With the distance calculated, the sensor can determine the liquid level within the container or tank. It knows that the distance between the sensor and the liquid's surface corresponds to the level of the liquid.
Output Signal: The sensor typically converts the calculated distance into an appropriate output signal, such as an analog voltage, a digital signal, or a current loop signal. This output can be used for various applications, such as displaying the liquid level on a screen, triggering alarms, or controlling liquid flow.
It's important to note that various factors such as temperature, humidity, and the nature of the liquid itself can affect the accuracy of the measurements. Advanced ultrasonic level sensors might incorporate features to compensate for these factors and provide more accurate readings.