Ultrasonic Level Sensing sensors and transmitters are used for continuous, non-contact level measurement.
Ultrasonic Level Sensing is a low-cost liquid level measurement technology. Ultrasonic Level Sensing sensors and transmitters are used for tank or river level measurement. Ultrasonic Level Sensing does not need to contact the medium, can be continuously measured, low cost. Therefore, Ultrasonic Level Sensing is very popular among users. Ultrasonic liquid level sensors are available in general and intrinsically safe types. Output 4~20mA standard signal or output the measurement result to the secondary meter through RS-485. Meets the system’s automatic control.
Featured Non Contact Ultrasonic Level Sensing Devices
What is Ultrasonic Level Measurement?
Ultrasonic Level Sensing measures liquid levels based on the principle of ultrasound. When ultrasonic waves encounter a high-density medium while propagating in a low-density medium, they cannot penetrate the high-density medium. There will be reflections at the interface of the two media. The ultrasonic liquid level gauge is made using this feature.
In the measurement, the ultrasonic pulse is emitted by the sensor (transducer), and the sound wave is reflected by the liquid surface and then received by the same sensor or ultrasonic receiver. Through piezoelectric crystal or magnetostrictive device into electrical signals. The distance between the sensor and the measured liquid surface is calculated by the time between the transmission and reception of sound waves.
Due to the non-contact measurement, the measured medium is almost unlimited. It can be widely used to measure the height of various liquid and solid materials.
The ultrasonic liquid level transmitter is composed of three parts: ultrasonic transducer, processing unit and output unit.
Ultrasonic Level Sensor Working Principle
The working principle of the ultrasonic liquid level sensor is:
Ultrasonic transducer (probe) emits high-frequency pulse sound waves, and the surface of the measured level (material) is reflected back. The reflected echo is received by the transducer and converted into an electrical signal. The propagation time of the sound wave is proportional to the distance from the sound wave to the surface of the object.
The relationship between the sound wave transmission distance S and the sound speed C and the sound transmission time T can be expressed by the formula: S=C×T/2.
The probe part emits ultrasonic waves, which are then reflected by the liquid surface. The probe part is received again. The distance from the probe to the liquid (object) surface is proportional to the elapsed time of the ultrasonic wave:
hb = CT2
Distance [m] = time × speed of sound/2 [m]
The temperature compensation formula of sound velocity:
Ambient sound velocity = 331.5 + 0.6 × temperature
Ultrasonic Level Sensor Advantages and Disadvantages
The advantages of ultrasonic liquid level gauge are very outstanding. It is mainly reflected in the following aspects:
- The structure is simple. The reading is convenient. It is very easy to install and maintain.
- Safe and clean. The instrument has long service life. The measurement is stable and reliable with high precision.
- Adopt non-contact measurement. It is not easily affected by the viscosity and density of the liquid.
Of course, the ultrasonic liquid level gauge also has its own limitations and insurmountable defects. Specifically, it is mainly manifested in:
- There is a blind spot in the ultrasonic liquid level measurement. The dead zone is the area where the meter cannot measure. During the transmission of ultrasonic pulses, a small area near the ultrasonic transducer usually cannot receive sound waves. The blind zone where sound waves cannot be received is related to the measurement distance of ultrasonic waves. Generally speaking, the smaller the measurement distance, the smaller the blind zone. The larger the measurement distance, the larger the blind zone;
- Ultrasonic liquid level measurement is easily affected by temperature. In the actual measurement, the change of temperature will cause the change of sound speed. This will lead to errors in the measurement;
- There should be no obstacles under the sound wave. Because the ultrasonic liquid level meter uses the principle of sound wave reflection to achieve liquid level measurement. If there are obstacles, it will affect the ultrasonic emission, causing signal loss and affecting the measurement effect;
- Ultrasonic liquid level gauge should not be used to measure pressure vessels. Because the pressure mainly affects the probe. There is also a certain relationship between the pressure and the temperature. The change in pressure will affect the change in temperature. This will affect the change in the speed of sound. The accuracy of the measurement will be affected;
- Ultrasonic liquid level gauge can not be used in the occasions with water mist, medium that is easy to produce a lot of foam, and volatile medium. Because this kind of working condition is easy to absorb the sound wave or interfere with the sound wave emission, the signal is lost and the accuracy is reduced;
- Ultrasonic liquid level gauge is greatly affected by dust. This is because although the dust environment has little effect on the speed of sound, it has a very significant effect on the attenuation of sound waves. Therefore, it is best not to use an ultrasonic level gauge in the presence of dust.
Can ultrasonic sensor detect water level?
Ultrasonic liquid level sensor can be used for water level measurement. The principle of ultrasonic reflection used. According to the contact between the sound wave emitted by the pool ultrasonic liquid level gauge and the liquid surface. According to the length of time it reflects back. To measure the height of the liquid level in the tank.
Liquid level sensors are used in many sites to detect some conditions that require liquid level monitoring. It is well known that the liquid level of some sewage treatment tanks, the liquid level on the tank, the liquid level on the river channel and so on.
How does a capacitive level sensor work?
The principle of capacitive level measurement，
is based on the capacitance change of a capacitor.
The probe and the tank wall form a capacitor,
whose capacitance is dependent on the amount of product in the tank:
An empty tank has a lower, a filled tank a higher capacitance.
A simple capacitor consists of two electrode plate,
separated by a small thickness of an insulator,
such as solid,
liquid, gas, or vacuum.
This insulator is also called as dielectric.
Value of C depends on dielectric used,
area of the plate and also distance between the plates.
C = capacitance in picofarads (pF)
E = a constant known as the absolute permittivity of free space
K = relative dielectric constant of the insulating material
A = effective area of the conductors
d = distance between the conductors
This change in capacitance can be measured using AC bridge.
How does water level sensor work?
There are many types of water level sensors. Including single flange static pressure / double flange differential pressure water level sensor, float type water level sensor, magnetic water level sensor, input type water level sensor, electric inner float water level sensor, electric float level sensor, capacitive water level sensor, magnetostrictive Water level sensor, servo water level sensor, etc., ultrasonic water level sensor, radar water level sensor, etc. It can be divided into contact type and non-contact type.
Extended reading: Radar Non Contact Water Level Sensor
How does a radar level transmitter work?
In radar level measurement,
microwaves are transmitted by the antenna system of the radar sensor,
to the measured product, reflected by the product surface,
and received back by the antenna system.
The time from emission to reception of the signals is proportional to the level in the vessel.
In continuous non-contact level measurement with radar,
the sensor sends microwave signals towards the medium from above.
The surface of the medium reflects the signals back in the direction of the sensor.
Using the received microwave signals,
the sensor determines the distance to the product surface
and calculates the level from it.
Liquids and solids are commonly measured with this measuring technique.
Sino-Inst offers over 10 Ultrasonic Level Sensing sensors and transmitters for level measurement. About 50% of these are float liquid level meters, 40% is the level switches.
A wide variety of Ultrasonic Level Sensing sensors and transmitters options are available to you, such as free samples, paid samples.
Sino-Inst is a globally recognized supplier and manufacturer of Ultrasonic Level Sensing sensors and transmitters instrumentation, located in China.
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