Measurement accuracy generally refers to the affirmative accuracy of the measurement value of the analog output. Depending on the echo transmission moment, the measurement accuracy of the ultrasonic sensor relies on several physical parameters. These parameters are generally related to air and internal errors.
Environmental impact
Air temperature
Air temperature has a great influence on the measurement accuracy of ultrasonic sensors. After the transmission time of the echo of the ultrasonic pulse is measured, the sensor calculates the interval between the target objects using the speed of sound. However, due to changes in air temperature, the speed of sound varies by 0.17% per Kelvin. Almost all ultrasonic sensors have a temperature detector to compensate for this effect. This detector measures the ambient temperature, and the sensor corrects the temperature offset associated with the measured value (see Temperature Compensation for details).
humidity
At room temperature and lower temperatures, the effect of humidity on the speed of sound is negligible. However, at high temperatures, the speed of sound increases with increasing humidity.
atmospheric pressure
The speed of sound drops by less than 1% at sea level and at an altitude of 3,000 meters. Atmospheric fluctuations at a given location are negligible, and the effect on the speed of sound is difficult to measure.
airflow
If the target object has the reflective characteristics of a standard reflector, the general air flow (wind) of 7 kN (50-61.5 km/h) has no effect on the ultrasonic measurement. Stormy climates may cause hurricanes to cause unstable measurements (signal attenuation). Regarding the change in the speed of sound, no conventional conclusions were drawn. This is because the direction and velocity of the airflow change from time to time. For example, hot objects, such as hot metals, can cause severe air disturbances. Ultrasound waves can be sloppy or violated, with no measurable echo returning.
Paint mist
The paint mist has no significant effect on the operation of the ultrasonic sensor. However, fog does not allow accumulation on the surface of the transducer during the operation to avoid affecting the sensitivity of the transducer.
External noise
External noise is different from the echo of the target object being measured, and generally does not cause false positives. If the source of interference is at the same frequency as the ultrasonic sensor, the amplitude of the internal noise must not exceed the amplitude of the policy echo. For example, this can happen when a silo is filled with stones.
Type of gas
Our ultrasonic sensors are designed for use in the atmosphere. Working in other gases, such as carbon dioxide, can lead to serious measurement errors or even total loss of functionality due to errors and attenuation of the speed of sound.
Temperature compensation
Ultrasonic sensors use the principle of echo transmission time, that is, the time interval between measuring the emission of ultrasonic pulses and measuring echoes. The ultrasonic sensor calculates the spacing of the target object by the speed of sound. When sound is transmitted in the air, the speed of sound is about 344 m/s at room temperature. But. The speed of sound is temperature-dependent, about 17% for every degree Celsius increase. Most of our ultrasonic sensors are capable of operating in the temperature range from -25° C to +70° C.
Without temperature compensation and a measurement interval of 100 cm, a temperature change of 20° C can result in an error of -8.5 cm at 70° C and an error of +7.65 cm at -25° C.
For this reason, most ultrasonic sensors are equipped with a temperature detector for the correction of the measurement interval. This compensation can be performed on the working scale of the ultrasonic sensor from -25° C to +70° C and achieves a measurement accuracy of ± 1.5%.
precision
Accuracy/Certainty refers to the difference between the output value and the measured value, which is the interval between the measured objects in the practice of the ultrasonic sensor. From a practical point of view, in industrial use, ultrasonic sensors are able to achieve a certain accuracy of 1 to 3 percent at operating scales from -25° to +70° C. High accuracy can be achieved under very stable ambient conditions. In this case, it is possible to turn off temperature compensation.
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