Which sensor technology shines in which application?

When looking for motion detectors, there’s no way around passive infrared measurement technology. This sensor technology has made a name for itself as a solution for low-budget markets. Radar, on the other hand, is still regarded as an emerging underdog in this segment. This raises the question for sensor integrators: established PIR technology or emerging radar technology? In order to determine the answer, manufacturers must be informed about both measurement technologies, know the differences, and weigh the advantages and drawbacks for their particular application. In order to help you make your decision, we’ve put together a little aid in this blog post comparing the two competitors.

Recording movement.

To start out, we’ll take a look at the tasks and expectations motion sensors face. The electronics are used to reliably detect movements within a limited coverage area and to pass on information about a movement event. And the forwarded information about the observed event enables systems, machines, or devices to be controlled automatically based on movements. The sensors are usually integrated into an end product and serve as a kind of trigger for further technical functions.

Popular technology.

We use the motion detection in many ways in everyday life. For example, it helps us save energy, provides convenience, or alerts us of unexpected movements. The technology is part of automation, and we increasingly encounter it in our own homes. Even toys and multimedia devices use such sensors to react to people’s presence.

The motion detectors trigger desired functions for us or alert us of something. For example, a person’s presence suffices to electronically open a door equipped with a motion sensor. Or we enter a room and the light goes on. When we leave the room, the light switches off again.

 

The current market for motion detection

Motion detection has a wide range of applications. This includes complex environmental detection and data analysis in the automotive or robotics industries. It is essential when it comes to security and surveillance functions in industry and the military.

But conventional applications of motion detectors are much simpler. The sensors don’t require complicated features, extensive information processing or complex integration and development work. Typical examples of this are opening doors, controlling lighting, and activating escalators. Many of these applications can be found in the highly contested consumer market, with its competitive pricing. Such sensors often have to be available in large volumes due to high demand for them and how useful they are, such as in the field of building technology.

For such use cases, the go-to solutions involve PIR or radar. Other technologies such as ultrasound and cameras are less commonly used (read more here). While PIR is extremely cheap and has proven itself as a motion sensor technology for years, radar has yet to hold its ground in the low-cost segment. But given the technical capabilities of radar sensors, this shouldn’t be a problem. When used in perimeter protection or vehicles, advanced radar technology has long been proving what it’s capable of and overcoming challenges infrared can’t handle. So far, however, radar’s price tag has been an issue when it comes to simple motion detection.

Only now, after years of development, has radar achieved an attractive price/performance ratio for use in motion detection. Its reduced cost is driving more and more manufacturers to see radar as a real alternative to PIR.

Let’s start this pros and cons regarding the use of PIR and radar for simple motion detection tasks.

Basic difference: the measuring principle

The two types of sensors work fundamentally differently. They operate in different wave spectra, and also the transmission and reception of signals work different. After all, as its name indicates, PIR is a passive measuring method for capturing motion information, while radar actively transmits pulses in search of movements.

What is PIR?

Passive infrared sensors detect heat radiation. Motion is detected based on people’s or animals’ body temperatures within the operating range. For this purpose, PIR measures changes in the thermal image of its environment over time. This measurement method records an event when the value of the heat radiation changes from one point in time to the next. If a person stands still, the sensor detects no change. As previously mentioned, this measuring technology is a passive detection method. The sensor doesn’t transmit signals itself in order to position movements or people’s and objects’ presence but merely receives the data emanating from a heat-emitting target in the event of a motion event.

What is radar?

Radar technology, for its part, entails active signal transmission and reception by utilising electromagnetic waves in the high-frequency range to detect objects, people, or animals within its coverage area. For this purpose, an antenna actively transmits a pulse with a certain frequency. This signal changes as soon as it hits a surface. The receiving antenna then receives the altered reflection and can analyse the change in the response signal. If a person moves within range, the received signal is modified over time. With motion detection, many sensors utilise the microwave range of 10 GHz. The 24 GHz frequency is, however, gradually gaining in popularity thanks to technological advances. Read more in our blog article 10 GHz vs 24 GHz.

Comparison – What is each technology capable of?

Now that we have clarified the different operating principles, let’s take a closer look at the resulting capabilities of the technologies. After all, PIR and radar feature different properties and present different challenges due to their respective measuring methods.

What is PIR capable of?

PIR is excellent at detecting living beings that move across to the sensor. The technology can also be used to measure temperatures. PIR sensors typically have an angle of vision of 120° and a maximum range of 10 m. Solar radiation doesn’t cause any problems, but light sources with high proportions of infrared and high temperatures do.

Other special characteristics of PIR sensors: The technology is extremely cheap. However, it requires a dome made of milky, plastic lenses. The sensors consume very little power.

What is radar capable of?

Radar, on the other hand, is not impacted by temperature, and the technology is considered suitable for all weather conditions. The radar waves penetrate plastics and can thus be placed behind different covers (e.g. a light switch). This sensor technology boasts high range and not only detects movement – it also provides further data such as speed, distance, direction of movement, and angular position for three-dimensional positioning in space. It does an excellent job at detecting objects or people moving frontally towards or away from the sensor. Through the additional measurement information, radars are also able to distinguish different objects within the detection range and identify them as single units. These capabilities entail more development work, resulting in higher costs. The signal processing also consumes more power.

Practical advantages and disadvantages

Especially when it comes to simple motion detection, technical fundamentals usually play a more minor role, since manufacturers primarily aim to implement the application in question. They always have the benefit to end users in mind. So what do these features actually mean for practical use?

PIR and radar put to the test:

The practical use of sensor technologies often presents them with different challenges. Since heat affects infrared sensors, for example, locations where the waste heat from heating or air conditioning systems is within range are detrimental to performance. Even a hair dryer can have a negative impact. Insulating clothing or contamination also prevents motion detection. In terms of weather, fog and direct sunlight pose another challenge for PIR. Since radar operates independently of weather and lighting conditions, the technology is often used in outdoor applications. Radar detection is much more sensitive than PIR and is thus also able to detect wind movements. To prevent false alarms from waving flags or trees, the sensors have filters and sensitivity configurations.

In a nutshell – the technical characteristics at a glance:

PIR:

+ movements along the side of the sensor

+ very low-cost

– movements occurring frontally to the sensor

– difficulties with high outside temperatures

– heat-insulating clothing reduces likelihood of detection

– limited range

– requires special lens

– no distinction between object types (person or animal)

– weather-sensitive

Radar:

+ more data

+ movements occurring frontally to the sensor

+ passes through materials

+ high range

+ multi-target capability

+ weather- and light-independent

– movements that are at an angle to the sensor

– higher-cost

What now?

The two technologies both have benefits and drawbacks, which you have to take into consideration for your application. Alternatively, the two are sometimes combined in solutions on the market: to compensate for the weaknesses of the respective sensor technologies, high-end motion detectors combine both. The dual-sensor approach is viewed to be highly reliable and greatly reduces the likelihood of false alarms. Only when both sensors detect a movement event does the dual sensor pass on the information. This variant is often used in the security sector.

If additional functions are required besides pure motion detection, such as adjustments to the sensitivity or duration as well as the detection of any presence or absence, this usually calls for more advanced technologies. Radar technology impresses here, because it can provide more data for configuration purposes.

After all this information, are you still having a hard time determining the right technology for your product? No problem – sensor pros don’t just appear out of nowhere. When it comes to radar technology, our experts will be happy to advise you in detail and discuss with you the possibilities and challenges presented by radar for your specific application. Especially when users require more than simple motion detection functions, radar boasts more possibilities.

Contactless and intelligent control for modern technology

Radar sensors take on many tasks for us, thus making our everyday lives easier, safer, and more efficient. They are a kind of sensory organ for objects for perceiving their surroundings. These technological assistants open up new possibilities for operating devices: contactless interaction between humans and devices. The sensors are the link for triggering or automating certain actions without contact or automating them.