Ultrasonic Sensors: How They Work

An ultrasonic sensorI remember when a car was a black box. It took me from point A to point B without fussing, and in satisfactory comfort. Then I got my driver’s license. Then I bought my first car. Now I manage the family fleet of two, and the car’s successful performance is quite a bit more critical than it was when I was fifteen.

Ultrasonic sensors, thankfully, are not as complex as cars. However, to many operators and engineers, they are little black boxes. This post aims to explain ultrasonic sensing technology. After all, it’s pretty simple, and it just may help you keep your sensors running optimally.

As you might gather, an ultrasonic sensor works by using the principles of sound. The term ultrasonic actually means ‘above human hearing’, as the sensor uses a frequency that we cannot hear. This is actually important to the function of the sensor, because...

Ultrasonic Sensor Mounting Q&A

Ultrasonic sensor mounted on a remote tankIs the sensor mounted perpendicular to the target?

Even just a few degrees off perpendicular can cause a loss of signal or result in the detection of an unwanted echo reflection. This becomes even more critical when trying to detect targets that are near the range limits of a given sensor.

Is there an adequate clear path from the face of the sensor to the target?

Keep in mind that we’re dealing with sound-wave signals, which spread in the shape of a cone similar to the beam of a flashlight. So what constitutes an “adequate” path? The answer to that question can get a bit complicated. It depends on a few things, such as the sensitivity & pulse settings, the furthest distance to the target, and the reflective characteristics of any perimeter targets. To be on the safe side, you can always use the sensor's published specification for beam spread as a guideline (APG uses the maximum beam spread as the specification).

Pressure Transducers: Proper Grounding

Grounding error caused even 316L stainless steel to erodeThere are generally two approaches to grounding pressure sensors. Both work just fine, as long as they are used in isolation. However, when both are used together, problems can occur.

The first is to use a chassis, or case, ground. This means that the manufacturer has designed the transducer to make contact to earth ground through the case/housing of the sensor. This approach allows the transducer to be naturally grounded during the installation process.

The second approach is to use a...