How does an Ultrasonic Level Transmitter work?

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How does an Ultrasonic Level Transmitter work?

An ultrasonic level transmitter is a non-contact type of level transmitter. Ultrasonic level transmitter is used for continuous level measurement in many industries. An ultrasonic level transmitter is the best choice for the measurement of water level in open sumps.

The ultrasonic level transmitter is mounted on the top of the tank whose level measurement is needed. Ultrasonic waves are transmitted from the ultrasonic level transmitter. These ultrasonic waves hit the top of the material in the tank. After hitting the material, the waves travel back to the transmitter. The transmitter has a microprocessor that calculates the time taken by the ultrasonic waves to go and come back.

Using a simple formula of distance i.e.

Distance = (speed of ultrasonic waves * time taken) / 2

 

We get the distance between the ultrasonic level transmitter and the material. In every ultrasonic level transmitter, a blocking distance parameter is entered. This blocking distance is nothing but the short range near the transmitter which the transmitter will not consider if waves come back from this distance. Another parameter named tank height is entered in the configuration.

From the figure,

Range = Distance + Level

The range is known quantity. Distance is calculated by the ultrasonic level transmitter using speed = distance/time. Hence, we get the level measurement. This all process is done inside the ultrasonic level transmitter using a microprocessor itself.

The ultrasonic waves are produced by a piezoelectric crystal. This piezoelectric crystal receives electrical energy as input and gives output as ultrasonic waves. Various frequencies of ultrasonic waves are produced by these piezoelectric crystals. The range varies from 15 to 200 kHz. The ultrasonic waves are nothing but a kind of mechanical wave.

These waves require a medium for traveling. So, we can use the ultrasonic level transmitter in tanks where the medium is air or pressurized medium. We cannot use the ultrasonic level transmitter in applications where the medium is the vacuum. Because ultrasonic waves cannot travel in a vacuum. Mostly you can see a majority of ultrasonic level transmitters in Effluent Treatment Plants for measurement of water level in sumps.

Advantages of Ultrasonic Level Transmitter

1. Level detection without physical contact with the medium is possible in an ultrasonic level transmitter
2. It has a large measuring up to 6 meters
3. This type of transmitter can detect a variety of objects like liquid level, solid level, foam level, and many more
4. As there is no moving part in an ultrasonic level transmitter, they are almost maintenance-free.
5. Configuration of ultrasonic level transmitters is very easy. Only a few parameters like tank height, blocking distance, and damping are essential for the basic functioning of this transmitter.
6. The cost of ultrasonic level transmitters is low compared to that of other non-contact type level transmitters like radar type level transmitters.

 

Disadvantages of Ultrasonic Level Transmitter

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1. We cannot use an ultrasonic level transmitter in vacuum service. This is because ultrasonic waves are a kind of mechanical waves and they require a medium to travel
2. The ultrasonic transmitter cannot be used in mediums that absorb the ultrasonic waves.
3. Change in temperature cause change in the speed of the ultrasonic waves. Hence, we will also get a change in the height obtained. So, temperature compensation is must required.
4. The ultrasonic level transmitter cannot be used in high-temperature service. Because the sensor is made up of a kind of polymer only.
5. Sometimes, moisture droplets get attached to the sensor tip. Because of this ultrasonic level transmitter starts showing 100% level. Hence removing the ultrasonic level transmitter and cleaning the ultrasonic level transmitter becomes necessary.

Applications of Ultrasonic Level Transmitter

1. Food & Beverage industry
2. Chemical industry
3. Tank water level measurement
4. Open tank level measurement

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Ultrasonic level transmitter is a highly technical device widely used in the industrial field, which utilizes the propagation characteristics of ultrasonic waves to measure the liquid level in liquid or solid containers. Its working principle is based on sophisticated ultrasonic technology, which provides a high-precision, non-contact liquid-level measurement solution for industrial process control and monitoring.

What is an ultrasonic level transmitter?

An ultrasonic level meter transmitter is a device used to measure the height of liquid levels in liquid or solid containers. It measures the liquid level by using ultrasonic technology and then converts these measurements into a standard signal to monitor, control, or display the level information.

Working Principle

Utilizing the velocity of propagation of ultrasonic waves, the height of a liquid level is calculated by transmitting an ultrasonic signal and receiving its reflection. A liquid-level meter transmitter typically consists of an ultrasonic transducer and an electronic transmitter unit. The transducer is mounted on top of the vessel, while the transmitter unit is used to process the ultrasonic data collected by the transducer and convert it to a standard current signal (e.g., 4-20 mA) or other communication protocols for connection to a monitoring system or control system.

Ultrasonic transmitter work to measure the liquid level simple diagram

Ultrasonic Level Transmitter Applications

• Chemical Industry
• Oil and gas industry
• Food and Beverage Production
• Water and wastewater treatment
• Pharmaceutical industry
• Environmental monitoring

Types of Ultrasonic Level Transmitters

1. Tank Ultrasonic Level Transmitter: Mounted on the side wall of a liquid vessel, the level is determined by measuring the distance from the sensor to the liquid surface. Suitable for liquid level monitoring in tanks or troughs.
2. Immersion ultrasonic level transmitter: immersed sensor in the liquid, measuring the distance from the liquid surface to the sensor. Suitable for liquid-level monitoring in liquids.
3. Pulsed Ultrasonic Level Transmitter: Uses pulsed ultrasonic waves to measure the distance from the liquid surface with high accuracy and stability. Suitable for applications requiring higher accuracy.
4. Digital ultrasonic level transmitter: output digital signal, with higher anti-interference ability and signal processing ability, suitable for complex industrial environments.

Differences Between Transmitters And Sensors

Ultrasonic level sensors typically include two main components: an ultrasonic level sensor and a transmitter. Although they are usually used together, they have different functions and roles:

FeaturesSensorsTransmitterFunctionMeasure the liquid level height and output the corresponding electrical signal or data.Measurement of the liquid level, conversion to a standard signal and transmission to the monitoring system.Output signalsDigital signal or analog signal, directly connected to the control system.Standard signals (e.g. 4-20 mA) or digital signals for monitoring and control.Fields of applicationReal-time monitoring and measurement of liquid or solid levels.Integration into automation systems for level monitoring and control.Installation and connectionDirectly connected to a monitoring device or control system.Often requires additional transmitters to be connected to the monitoring system.Communication protocolsMay use fieldbus protocols or proprietary communication protocols.Standard communication protocols, e.g. HART, Modbus, etc.Functional add-onsOften simplified and focused on measurement functions.May have additional features such as auto-calibration, remote monitoring, etc.ComplexityTypically simpler, suitable for stand-alone level measurement tasks.More complex, suitable for integration into complex control systems.Table of Differences Between Transmitters And Sensors

How to use ultrasonic level transmitter?

Mounting the ultrasonic sensor: Mount the ultrasonic sensor on a liquid or solid vessel. The mounting location should be free from obstructions, vibrations and other factors affecting the measurement. Make sure that the position of the transducer is accessible for ultrasonic emission and reception and is not obstructed by the medium.
Power supply connection: Connect the ultrasonic level transmitter to the power supply. Typically, ultrasonic-level transmitters use a DC power supply, so make sure the correct supply voltage is provided.
Signal Connection: Typically, this is done via a 4-20mA current signal or other standard industrial communication protocol.
Setting operating parameters: Set the operating parameters of the ultrasonic level transmitter according to the specific application requirements.
Avoid interference: Consider and avoid factors that may interfere with the measurement results, such as high wind, strong vibration, temperature changes, etc.
Test and calibration: Test and calibrate before formal operation. Verify the performance and accuracy of the ultrasonic level transmitter by simulating or actual level changes.
Monitoring and Maintenance: Regularly monitor the performance of the ultrasonic level transmitter to ensure that it is stable and reliable. If abnormalities are found, recalibration or overhaul may be required.
Safety Precautions: Follow safety regulations and instructions to ensure safe use of the ultrasonic level transmitter. For example, avoid direct exposure to ultrasonic radiation.

Advantages Of The Transmitter

• Non-contact measurement
• Wide range of applications
• High precision
• High stability
• Unaffected by the medium

Limitations of The Transmitter

Affected by temperature and humidity: High temperature, high humidity or extreme temperature conditions may affect the performance of the ultrasonic level transmitter.

Bubbles and foam effects: liquid bubbles or foam may affect the propagation of ultrasound, thus affecting the measurement accuracy.

Not applicable to gas measurement: the ultrasonic level transmitter is mainly used for liquid measurement, not for gas measurement.

Limitations of volatile liquids: For volatile liquid applications, may need to consider the impact of volatile substances on the sensor performance.

Positioning requirements: The ultrasonic sensor installation location needs to be considered to avoid obstacles to ensure that the sensor works properly.

Summary

Ultrasonic-level transmitters play an important role in industrial automation due to their reliability, accuracy, and applicability. With the continuous development of technology, the working principle and performance of ultrasonic level transmitters are also constantly innovating and improving, providing reliable level monitoring and control means for various industries.

Apure is a supplier to the water treatment industry offering a wide range of water quality parameter analyzers, radar level meters, ultrasonic flow meters, pressure transmitters, temperature measurement and ozone generators. Feel free to contact us to develop a customized solution for you.