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What is an ultrasonic sensor?

Ultrasonic sensors are industrial control devices that use sound waves above 20,000Hz that exceed the range of human hearing to measure and calculate the distance from the sensor to the target object.

How do ultrasonic sensors work?

The sensor has a ceramic transducer that vibrates when electrical energy is applied to it. The vibration compresses and expands the air molecules in the wave from the sensor face to the target object. The transducer sends and receives sound. The ultrasonic sensor will measure the distance by emitting sound waves and then "listen" for a period of time, allowing the return sound waves to bounce off the target and then retransmit.

When to use an ultrasonic sensor?

Since ultrasonic sensors use sound as a transmission medium instead of light, they can be used in applications where optical sensors cannot be used. Ultrasonic sensors are a good solution for transparent object detection and level measurement, while photoelectric sensors are challenging due to target transparency. The target color and/or reflectivity do not affect the ultrasonic sensor that can operate reliably in high-glare environments.

When should you use an ultrasonic sensor compared to an optical sensor?

Ultrasonic sensors have an advantage when detecting transparent objects, liquid levels or highly reflective or metal surfaces. Ultrasonic sensors also work well in humidity environments because water droplets refract light. However, ultrasonic sensors are susceptible to temperature fluctuations or wind. With an optical sensor, you can also have a small spot size, a fast response, and in some cases, you can project a visible dot on the target to help the sensor align.

How do ultrasonic sensors handle noise and interference?

Any acoustic noise at the frequency received by the ultrasonic sensor may interfere with the output of that sensor. This includes high-pitched noises, such as those produced by whistles, safety valves, the hissing of compressed air or pneumatics. If you put two ultrasonic sensors of the same frequency together, you will have acoustic crosstalk. Another type of noise, electrical noise, is not what ultrasonic sensors do*.

What environmental conditions affect ultrasonic sensors?

Temperature fluctuations affect the speed of the sound waves of the ultrasonic sensor. As the temperature increases, the speed of the sound waves increases. While the target may not have shifted, the sensor feels that the target is closer. Airflow caused by pneumatic devices or fans can also deflect or disrupt the path of ultrasound. This can cause the sensor to not be able to identify the correct location of the target.

Why do I need to warm up the ultrasonic sensor before operation?

Ultrasonic sensors can only be configured and operated after they have been warmed up. When a sensor is powered on, the surrounding air and other components heat up due to the heating up of a single component. This temperature fluctuation from cold start to operating temperature is called "warm-up drift". Until all components have stabilized at the correct operating temperature, the accuracy of the measurement may be affected.

What is a blind spot?

The dead zone is the area directly in front of the sensor surface where the sensor cannot reliably measure. This is due to a phenomenon called ringing. Ringing is the continuous vibration of the sensor after an excitation pulse. Before the sensor can listen to the return echo, the energy must be dissipated. Make sure to target outside the blind zone of the ultrasonic sensor.

Are ultrasonic sensors slower than photoelectric sensors?

Yes. The speed of sound is much slower than the speed of light, so ultrasonic sensors will be inherently slower than light sensors.

What kind of targets should be avoided when using ultrasonic sensors?

The target for use with ultrasonic sensors is large, flat, solid surfaces of materials such as metal, ceramic, glass or wood. The target should always be placed perpendicular to the sensor. Soft or irregular surface targets such as particles, sawdust or foam should be avoided.

What is the * method of using ultrasound to detect randomly placed objects?

Teach the background of the sensor as a good state. By teaching the ultrasonic reflection of the background surface as a good condition, any object between the sensor and the background will be detected, resulting in output switching.

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