Ultrasonic sensors are unaffected by changes in air temperature (they have temperature compensation built in), air pressure and humidity. However, other factors can affect their performance.
Air turbulence – strong air turbulence can negatively influence the sound propagation and, consequently, the measurement. Sources of air turbulence include wind, compressed air and cooling fans. The influence can be minimised by physically shielding the sensor/ measuring distance from the turbulence.
Target material and surface characteristics – materials that absorb sound or surfaces that deflect sound away from the sensor are difficult to sense with diffuse mode ultrasonic sensors. A retro-reflective mode ultrasonic sensor may be the better solution here.
Target speed – diffuse mode ultrasonic sensors typically have switching frequencies of 10Hz or less and are not useful for high-speed applications.
Target size – targets must meet minimum size requirements to be reliably detected. The smaller the target, the shorter the sensing range at which it can be reliably detected by the ultrasonic sensor.
Target orientation – for diffuse ultrasonic applications, the face of the sensor should be parallel to the target. Deviations up to 4° can be tolerated on smooth surfaces.
Soiling of the face – small amounts of dust and moisture can be shed through the vibration of the transducer, but large amounts will degrade performance.
Crosstalk – ultrasonic sensors are prone to crosstalk if they are mounted too close together. Observe the mounting distances specified in the operating instructions.