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Influence Factors of Ultrasonic Transmitters

25 Jun, 2015 Ultrasonic Sensor
Ultrasonic Transmitters

Ultrasonic transmitters provide a reliable, non-contact detection method for eigher solid or liquid, But even so, there are many unfavorable factors on the operation of transmitters such as powder, wind, humidity, dust, fumes, etc. Here are some major influence factors listed as follows:

Influence of temperature & humidity on ultrasonic transmitters


The range of ultrasonic signals is influenced by the relative humidity and temperature of the air. In general, the sensing range decreases along with increasing temperature and increasing humidity. This reduction is not linear, and is different from transmitter to transmitter.

Air temperature is one of the important factors impacting on the measuring accuracy of an ultrasonic transmitter. When the temperature changes, the speed of ultrasound changes by 0.17% per degree Kelvin. So that most of ultrasonic transmitters have a temperature probe to compensate for this effect.

Humidity has few influence on the speed of ultrasound at lower or normal temperatures. However, on condition that higher air temperatures, the speed of ultrasound will increase with humidity increase.

Influence of air pressure & wind on ultrasonic transmitters


The speed of sound decreases by less than 1% from 0 ~ 3000 m altitude. Atmospheric fluctuations are negligible at a specific location and the influences on the speed of sound are hard to measure.

If the surface of object has the reflective properties, regular wind has no infulence on ultrasonic measurement to speeds of approx. 50-60 km/h. Because the direction and speed of wind constantly change, There are no general conclusions regarding changes of sound speed can be drawn. For instance, special hot objects can cause significant air turbulence, the ultrasound can be scattered or deflected in such condition that no echo can be returned.

Influence of weather on ultrasonic transmitters


Some extreme weathers cause unstable measurements, such as heavy fog, dust, rain and snow. They mayreduce the maximum range of ultrasonic transmitters. The light dirt and dust on transmitter surface will not influence measurement. Accumulation of water or snow should be avoided with appropriate solutions i.e. enclosures.

Influence of object surface on ultrasonic transmitters


The ultrasonic transmitters can recognize most materials and surfaces including solids, liquids or powders. Surface properties no matter rough or smooth, wet or dry, also have no infulence on detection results. However, the right angles are very essential for the best reflection, if the angle to the surface of object is not 90, the returning ultrasound will be deflected away from the transmitters, that means no longer be detectable. The reliable detection can be measured based on the higher amplitude of the reflec ultrasonic signal. On the other hand, high levels of dust or humidity can also reduce the sound energy and the maximum range of the ultrasonic transmitter.

Other influence factors on ultrasonic transmitters


The noise commonly does not cause issues. But if the source of disturbance has the same frequency as the ultrasonic transmitter, the level of the noise can't exceed the level of the target echoes, just as the example of filling a silo with stone. Ultrasonic transmitters are generally designed for operation in atmospheric air. If they are applied in other gases may cause serious measurement errors because deviation effect will be occurred in the speed of sound.

 
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