How do ultrasonic transmitters measure level

ultrasonic transmitters measure level

How do ultrasonic transmitters measure level. It is a widely used technique for accurately determining the level of liquids or solids in various industrial and environmental applications.

This non-contact method relies on the transmission and reception of ultrasonic waves to measure the distance between the sensor and the target surface, allowing for precise level calculations.

Ultrasonic transmitters, also known as ultrasonic level sensors or ultrasonic transducers, are the key components used in this measurement process.

These devices emit high-frequency sound waves, typically in the range of 20 kHz to 200 kHz, which are beyond the range of human hearing.

The emitted sound waves propagate through the air or a medium until they encounter a reflecting surface, such as the liquid level or solid material being measured.

The basic principle behind ultrasonic level measurement is the measurement of the time it takes for the ultrasonic waves to travel from the transmitter to the target surface and back to the receiver.

The transmitter emits a short pulse of ultrasonic waves, which travel at the speed of sound and reach the target surface. When the waves hit the surface, they are reflected back towards the receiver.

The receiver detects the reflected waves and measures the time it takes for them to return.

By knowing the speed of sound in the medium and measuring the time of flight, the distance between the sensor and the target surface can be calculated using simple mathematical equations. This distance corresponds to the level of the liquid or solid material being measured.

Ultrasonic level transmitters are versatile and can be used in various industries, including wastewater treatment plants, chemical processing, oil and gas, food and beverage, and many more.

They offer advantages such as non-contact measurement, high accuracy, wide measurement range, and resistance to environmental factors such as temperature, pressure, and chemical corrosion.

How do ultrasonic transmitters measure level

Let’s delve into the detailed workings of ultrasonic transmitters for level measurement.

Basic Components of an Ultrasonic Transmitter

An ultrasonic transmitter consists of the following key components:

  • Transducer: The transducer is the heart of the ultrasonic transmitter. It converts electrical energy into ultrasonic sound waves and vice versa. It typically comprises a piezoelectric crystal that expands or contracts when subjected to an electrical voltage, producing ultrasonic waves.
  • Electronics: The electronics module includes a circuit board that generates and controls the electrical signals to drive the transducer. It also processes the received signals to determine the level.
  • Housing: The housing encapsulates the transducer and electronics, providing protection and support for the device. It is designed to withstand environmental conditions and may have features like waterproofing or explosion-proofing, depending on the application requirements.

Working Principle of Ultrasonic Transmitters

The working principle of an ultrasonic transmitter involves the following steps:

  • Transmission: The transmitter emits a short burst or pulse of ultrasonic waves. The waves travel through the air or a medium, such as a liquid or solid, until they encounter a target surface.
  • Reflection: When the ultrasonic waves reach the target surface, they reflect back towards the sensor. The reflecting surface can be the liquid level, the surface of a solid material, or any other suitable reflecting surface.
  • Reception: The transducer, acting as a receiver, detects the reflected ultrasonic waves. The reflected waves cause the piezoelectric crystal in the transducer to vibrate, generating an electrical signal.
  • Time Measurement: The electronics module measures the time it takes for the ultrasonic waves to travel from the transmitter to the target surface and back to the receiver. This time, known as the “time of flight,” is crucial for calculating the distance between the sensor and the target surface.
  • Distance Calculation: By knowing the speed of sound in the medium, which depends on factors like temperature and pressure, the distance between the sensor and the target surface can be determined using the formula: [ Distance = (Speed of Sound × Time of Flight) / 2 ]. The division by 2 accounts for the round trip of the ultrasonic waves.
  • Level Calculation: Once the distance is known, it can be translated into the level of the liquid or solid being measured. The level is typically expressed in units of length, such as millimeters, centimeters, or inches, depending on the application.

Speed of Sound Considerations

The accurate measurement of distance and level using ultrasonic transmitters relies on knowing the speed of sound in the medium. The speed of sound varies with temperature, humidity, and the composition of the medium.

Therefore, it is essential to account for these factors to achieve precise measurements.

Manufacturers often provide calibration tables or algorithms that incorporate temperature compensation to correct for variations in the speed of sound.

These tables or algorithms allow the ultrasonic transmitter to compensate for changes in the medium’s properties and provide accurate level readings.

Signal Processing and Calibration

The electronics module of an ultrasonic transmitter plays a crucial role in processing the received signals and providing accurate level measurements.

Signal processing techniques are employed to filter out noise, enhance signal quality, and extract relevant information.

The received signal may contain unwanted echoes or interference from multiple reflections within the measurement environment.

Signal processing algorithms are used to identify the primary echo corresponding to the target surface and reject spurious echoes.

Filtering techniques, such as low-pass filters or Fourier analysis, can be employed to eliminate noise and enhance the quality of the received signal.

Calibration is an essential step to ensure the accuracy and reliability of ultrasonic level measurements. During calibration, the ultrasonic transmitter is set up in a known reference condition, and the corresponding level is determined.

This reference level is used to establish a relationship between the measured distance and the actual level.

Calibration factors can be programmed into the transmitter’s electronics to compensate for any inherent measurement errors and improve accuracy.

Application Considerations:

Ultrasonic transmitters are widely used for level measurement in various industries and applications. However, certain factors need to be considered for optimal performance:

  • Beam Angle and Beam Spread: Ultrasonic transmitters emit sound waves in a cone-shaped beam. The beam angle and spread determine the area of coverage and the accuracy of the measurements. A narrow beam angle provides focused measurements but may require precise alignment with the target surface. A wider beam angle offers broader coverage but may result in decreased accuracy due to potential interference from surrounding objects or surfaces.
  • Material Compatibility: Different ultrasonic transmitters are designed for specific environments and materials. It is important to select a transmitter that is compatible with the medium being measured. Factors such as chemical composition, temperature, and pressure should be considered to ensure the longevity and reliability of the device.
  • Environmental Factors: Ultrasonic transmitters are susceptible to environmental conditions that may affect their performance. Factors like temperature, humidity, dust, and atmospheric conditions can impact the speed of sound and introduce measurement errors. The datasheet or user manual provided by the manufacturer should include information on the device’s operating temperature range, humidity tolerance, and any necessary precautions for specific environments.
  • Obstructions and Interference: Ultrasonic transmitters rely on the reflection of sound waves to determine the level. Objects or obstructions in the path of the sound waves can interfere with the measurements. It is important to consider the presence of objects like pipes, supports, or agitators that may block or distort the sound waves. Proper placement and mounting of the transmitter can help minimize such interference.
  • Liquid Characteristics: When measuring the level of liquids, factors like density, viscosity, surface turbulence, and foam formation can influence the accuracy of the measurements. Some liquids may absorb or attenuate the ultrasonic waves, affecting the reliability of the readings. It is crucial to understand the properties of the liquid being measured and consider any necessary adjustments or calibration factors.

Advantages and Limitations:

Ultrasonic transmitters offer several advantages for level measurement:

  • Non-contact Measurement: Ultrasonic transmitters operate without physically contacting the measured substance, minimizing the risk of contamination or interference with the process.
  • Wide Range: Ultrasonic level measurement can cover a wide range of distances, from a few centimeters to several meters, making it suitable for various applications.
  • High Accuracy: With proper calibration and installation, ultrasonic transmitters can provide accurate and repeatable level measurements.
  • Versatility: Ultrasonic transmitters can be used for measuring the level of liquids, slurries, and solids in different industries such as water treatment, chemical processing, food and beverage, and oil and gas.

However, ultrasonic level measurement also has certain limitations:

  • Limited Performance in Certain Environments: Ultrasonic transmitters may face challenges in environments with heavy dust, steam, or mist, as these can interfere with the sound waves and affect measurement accuracy.
  • Beam Angle and Interference: The cone-shaped beam emitted by ultrasonic transmitters can result in interference from surrounding objects, leading to measurement errors or false readings. Careful positioning and beam angle considerations are necessary to mitigate these issues.
  • Surface Reflections: Irregular or highly reflective surfaces can cause multiple echoes, making it challenging to identify the primary echo corresponding to the target surface. Signal processing techniques are employed to filter out unwanted echoes and identify the correct measurement.
  • Limited Suitability for Some Materials: Certain materials, such as soft or porous solids, may absorb or attenuate the ultrasonic waves, limiting the effectiveness of ultrasonic level measurement.


In conclusion, ultrasonic transmitters are valuable tools for accurate and reliable level measurement. Their non-contact nature, wide measurement range, and high accuracy make them suitable for diverse industrial applications.

By understanding the working principle, considering environmental factors, and properly calibrating the devices, ultrasonic transmitters can provide precise level measurements, contributing to efficient and safe processes in various industries.

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