Ultrasonic level sensor is a kind of sensor that utilizes ultrasonic principle to measure the height of liquid level. It has the advantages of non-contact, non-invasive, high reliability, etc. It is widely used in industry, agriculture, commerce and other fields.
What is an ultrasonic level sensor?
Definition
Ultrasonic level sensors are sensors that utilize the characteristics of ultrasonic wave propagation to calculate the liquid level height by measuring the time it takes for the emitted ultrasonic pulse to be reflected back from the liquid surface.
Basic Principle
The sensor transmits ultrasonic pulses, which propagate through the liquid and are reflected when they meet the liquid surface. The sensor receives the reflected pulses and calculates the liquid level height based on the pulse propagation time and the speed of sound.
Or:
The ultrasonic level sensor utilizes the characteristic of ultrasonic wave propagation in liquid, and calculates the liquid level height by measuring the time from transmitting ultrasonic pulse to reflecting back from the liquid surface.
The ultrasonic pulses usually have a frequency of 20kHz-100kHz and a wavelength of 1-10cm.
Advantages of ultrasonic sensors over other horizontal sensing technologies
- Non-contact, non-invasive: the ultrasonic sensor does not come into direct contact with the liquid and therefore does not interfere with the flow of the liquid. This is very advantageous for measuring liquids that are easily corroded, contaminated or contain solid particles.
- High reliability: ultrasonic sensors are not affected by liquid contamination and are therefore highly reliable. This is very advantageous for measuring liquids that have been in harsh environments for a long time.
- Wide measuring range: ultrasonic sensors can measure the depth or height of liquids over a range of up to several tens of meters. This is very advantageous for measuring liquid levels in large vessels.
Below is a comparison of ultrasonic level sensors with other level sensing technologies:
| Technology | Advantages | Disadvantages |
| Ultrasonic | Non-contact, non-invasive, reliable, wide measurement range | Higher price, susceptible to noise interference |
| Capacitive(KS-SMY1 Capacitive Water Level Sensor) | Low cost, high measurement accuracy | Susceptible to contamination, narrow measurement range |
| Optical | High measurement accuracy, wide measurement range | Susceptible to contamination, susceptible to light interference |
| Float(UHZ Liquid Float Magnetic Level Gauge) | Low cost, reliable | Narrow measurement range, susceptible to liquid agitation |
Ultrasonic level sensor components and types
The ultrasonic level sensor is mainly composed of the following components:
- Transmitter: for transmitting ultrasonic pulses.
- Receiver: for receiving the reflected wave of ultrasonic pulse.
- Signal processor: used to calculate the liquid level height.
In addition, ultrasonic level sensors can be categorized into the following two types according to their measurement method:
- Single transmitter single receiver type: this type of sensor has only one transmitter and one receiver. The transmitter transmits ultrasonic pulses and the receiver receives the reflected waves of the ultrasonic pulses. Based on the propagation time of the pulse and the speed of sound, the level height can be calculated.
- Multi-transmitter, multi-receiver type: This type of sensor has multiple transmitters and multiple receivers. The transmitters transmit ultrasonic pulses sequentially and the receivers receive the reflected waves of the ultrasonic pulses sequentially. Based on the propagation time of the pulses and the speed of sound, the liquid level height can be calculated.
Single transmitter single receiver type ultrasonic level sensor
The single transmitter single receiver type ultrasonic level sensor has a simple structure and low cost. However, the measurement accuracy of this type of sensor is lower and more affected by liquid shaking.
- Non-contact ultrasonic liquid level sensor
Multi-transmitter and multi-receiver ultrasonic liquid level sensor
- Non-contact ultrasonic level sensor
Multi-transmitter, multi-receiver type ultrasonic level sensors have higher measurement accuracy and are less affected by liquid shaking. However, this type of sensor has a complex structure and higher cost.
Different types of ultrasonic level sensors
Ultrasonic level sensors can be divided into the following types according to their measuring principle and structural characteristics:
- Non-contact ultrasonic level sensor: this type of sensor determines the liquid level height by measuring the ultrasonic wave propagation time, without direct contact with the liquid, so it has the advantages of non-contact, non-invasive and high reliability.
- Contact ultrasonic level sensor: this type of sensor will sensor probe directly contact with the surface of the liquid, through the measurement of ultrasonic wave propagation time in the liquid to determine the liquid level height.
- Waveguide ultrasonic level sensor: this type of sensor directs ultrasonic waves to the surface of the liquid and then measures the echo time to determine the liquid level height.
Non-contact ultrasonic level sensor
Non-contact ultrasonic level sensors are the most common type of ultrasonic level sensor. This type of sensor determines the liquid level height by measuring the ultrasonic wave propagation time without direct contact with the liquid, so it has the advantages of non-contact, non-invasive and high reliability.
Contact ultrasonic level sensors can be categorized into the following two types according to the shape of their probes:
- Cylindrical probe type: this type of probe has a large measuring range and is suitable for measuring the liquid level in large vessels.
- Flat plate-shaped probe type: this type of probe has a high measurement accuracy and is suitable for measuring the liquid level in small containers.
Waveguide type ultrasonic level sensor
Waveguide type ultrasonic level sensors have higher measurement accuracy and are less affected by liquid shaking. However, this type of sensor has a complex structure and high cost.
Waveguide ultrasonic level sensors can also be categorized into cylindrical waveguide type and flat waveguide type according to the shape of its waveguide.
The following factors need to be considered when selecting the type of ultrasonic level sensor required for a particular application:
- Measuring range: The measuring range of an ultrasonic level sensor depends on the distance between its transmitter and receiver. For measuring the level in large vessels, you need to choose a sensor with a large measuring range; for measuring the level in small vessels, you need to choose a sensor with a smaller measuring range.
- Measurement accuracy: The measurement accuracy of ultrasonic level sensors depends on the performance of their transmitters and receivers. For applications requiring high measurement accuracy, it is necessary to select a sensor with high measurement accuracy.
- Environmental conditions: The operating environment of ultrasonic level sensors affects their performance. For sensors operating in harsh environments, it is necessary to select sensors with high reliability.
Below are some specific application scenarios and suggested sensor types:
- Liquid level measurement in large vessels such as water tanks and oil tanks: you can choose contact or waveguide ultrasonic level sensors. Contact sensors have simple structure and lower cost, but lower measurement accuracy; waveguide sensors have higher measurement accuracy, but complex structure and higher cost.
- Liquid level measurement in small containers: non-contact ultrasonic level sensors can be selected. Non-contact sensors do not need to be in direct contact with the liquid, so they have the advantages of non-contact, non-intrusive and high reliability.
- Measurement of liquids that are easily corroded, easily contaminated or contain solid particles: non-contact ultrasonic level sensors can be selected. Non-contact sensors do not come into direct contact with the liquid, so they are not affected by liquid contamination.
- Sensors operating in harsh environments: sensors with high reliability can be selected. For example, sensors working in vibration or noise environments need to choose sensors with anti-vibration and anti-noise capabilities.
Ultrasonic level sensors in the application of various industries
Manufacturing industry
In the manufacturing industry, ultrasonic level sensors are mainly used in the following applications:
- Liquid level monitoring and control of storage tanks, tanks, pipelines and other vessels
- Liquid flow measurement in production lines
- Liquid composition analysis in chemical and metallurgical industries
For example, in the petroleum and chemical industries, ultrasonic level sensors can be used for liquid level measurement in tanks, chemical reactors and other equipment to ensure production safety. In the automotive manufacturing industry, ultrasonic level sensors can be used for liquid flow measurement on production lines to improve production efficiency.
Water treatment
In the water treatment industry, ultrasonic level sensors are mainly used in the following applications:
- Sludge concentration measurement in sewage treatment plants
- Liquid level monitoring in reservoirs, cisterns and other water bodies
- Liquid flow measurement in drinking water purification systems
For example, in wastewater treatment plants, ultrasonic level sensors can be used for sludge concentration measurement to control the sludge treatment effect. Liquid level monitoring in water bodies such as reservoirs and cisterns to ensure water safety.
Agriculture
In agriculture, ultrasonic level sensors are mainly used in the following applications:
- Liquid level monitoring in agricultural irrigation systems
- Feed liquid supply in livestock farming industry
- Water level monitoring in aquaculture industry
For example, in farmland irrigation systems, ultrasonic level sensors can be used for liquid level monitoring to ensure an even supply of irrigation water. In livestock farming, ultrasonic level sensors can be used for feed liquid supply to improve feed utilization.
Other industries
Ultrasonic level sensors can also be used in environmental monitoring, medical equipment and other fields. For example, in environmental monitoring, ultrasonic level sensors can be used for the concentration measurement of pollutants in water bodies. In medical equipment, ultrasonic level sensors can be used for volume measurement of blood, urine and other liquids.
Limitations of ultrasonic level sensors
Environmental factors
- Dust, foam, and vapor: Airborne particles like dust and bubbles can absorb or scatter the sound waves, leading to inaccurate or erratic readings. Foaming liquids pose similar challenges, while dense vapors from certain chemicals can completely block the signal.
- Temperature and pressure changes: Extreme temperatures and pressure fluctuations can affect the speed of sound, impacting the accuracy of distance measurements. This is particularly relevant in outdoor applications with significant weather variations.
- Turbulent liquids and surface conditions: Agitated liquids and rough surfaces can cause sound waves to reflect at multiple angles, making it difficult to determine the true level. Stirrers, waves, and even wind over liquid surfaces can further complicate readings.
- Material compatibility: Certain chemicals or highly corrosive substances can damage the sensor’s transducer, impacting its performance and requiring frequent replacements.
- Mounting considerations: Sensor alignment and distance from the target material are crucial for accurate readings. Inaccessible or awkward tank geometries can make these aspects challenging.
Maintenance concerns
- Sensor fouling: Dust, dirt, and other build-up on the transducer can significantly weaken the sound waves, affecting measurement accuracy. Regular cleaning and maintenance are essential.
- Calibration needs: Over time, sensors can drift in their accuracy, requiring periodic calibration to ensure reliable measurements. This adds to the overall maintenance costs.
- Limited range: Compared to other technologies like laser level sensors, ultrasonic sensors have a shorter effective range. For deep tanks or large containers, they might not be the most suitable option.
- Power consumption: While some models are energy-efficient, continuous operation can drain batteries faster, requiring more frequent replacements or dedicated power sources.
Addressing the challenges
Despite these limitations, several strategies can minimize their impact and ensure successful ultrasonic level measurement:
- Selecting the right sensor: Choosing a sensor with features like signal filtering, temperature compensation, and self-cleaning capabilities can mitigate environmental challenges.
- Proper installation and calibration: Ensuring correct sensor alignment, distance, and initial calibration is crucial for optimal performance.
- Regular maintenance: Implementing cleaning schedules and periodic calibration checks will keep the sensor functioning accurately.
- Considering alternative technologies: For specific applications with challenging environmental conditions or extended measuring ranges, other level measurement technologies might be more suitable.
Summary
Ultrasonic level sensors have become an indispensable key element in modern industry with their non-contact measurement, high precision reliability and wide applicability. Its ability to accurately monitor the distance and level of liquids or solids to improve productivity and safety, and plays a key role in many fields such as manufacturing, medical, environmental protection, etc., providing important support for automated processes and technological innovation.
Apure offers not only level measurement instruments, but also water quality analysis instruments, flow measurement tools, pressure measurement tools and temperature measurement tools. If you have questions please feel free to contact us.