Are you using the right motion detection technology?

There are many different options for motion detection, but which one best suits your needs? Here is a look at some of the most widely used motion sensor technologies and the situations in which each can be used to its strengths.

Choosing the right tool for the job

An important and often overlooked factor when choosing new components for your security system is how well they will integrate with your existing network. Security systems are at their most effective when made up of a collection of best-in-breed components working seamlessly together. So, before deciding on a new component for your system, ask yourself how it will fit into your existing network and whether it will work with components you might want to add in the future.

There will be significant differences in quality and effectiveness between the individual motion detection products looked at here – this is aimed at differentiating between the benefits of each technology when operating in the most appropriate environment.

Finally, and most importantly, choose a solution that fits the specific job. Every installation will come with its own challenges – be they budget constraints or challenging conditions – and each will require a tailored solution to meet the requirements.

PIR Sensors

Passive infrared (PIR) sensors detect changes in the amount of infrared radiation it picks up, and when a threshold limit is reached the sensor will trigger whatever it is connected to e.g. a light, alarm or camera. To learn more about how they work, click here.

This simple technology is effective in what it does, but the simplicity of the design brings with it inherent problems. For one, the output from the sensor is a very simple – switch the light on or don’t. The significance of this becomes apparent when compared to alternative technology in this post.

Negatives aside, PIR sensors are effective provided you are aware of their limitations and, given that they have been used in security systems for so long, they are also fairly affordable.

Video motion detection (VMD)

The VMD option combines the images generated by a security camera, with software that can analyse the images as they are captured. This takes place in much the same way as a camera operator sitting watching a video feed, but is automated and as such holds certain advantages (click here to learn more).

It is easy to visualise some of the downsides of this technology. Operating in the visible light spectrum, the camera is blind if there is not enough light, and open to blinding if there is too much backlight. On the upside, video is a widely implemented security solution and adding a layer of analytics is fairly cost-effective.

There are a wide range of VMD technologies out there – some will allow you to make tweaks to settings, e.g. to only detect motion within certain perimeters, and some will simply detect any movement.

Thermal cameras

Thermal cameras are not really cameras, in that they don’t pick up visible light, they are sensors that create an image based on temperature differences between objects in their ‘field of vision’. To learn more about how thermal cameras work, click here.

Thermal cameras are marvellous pieces of kit. They have an excellent range, even if they do focus on a fairly narrow area, can pick up heat signatures through smoke and fog and are immune to many conditions that would be problematic to visible light cameras – shadows, darkness, backlight and even camouflaged objects.

Whilst these thermal imaging cameras are highly effective, they do come with a similarly high price tag which can put the technology out of bounds in many cases.

Radar

Radar works by transmitting radio waves and receiving the same waves bounced off objects in its field of detection. In terms of usefulness in a security system, this technology calculates distance, velocity and size of objects in relation to the detector.

The benefit of using radio waves over infrared or visible light is a comparative lack of interference caused by triggers of false alarms. Radio waves pass through objects such as spider webs, leaves and smoke, allowing radar equipment to focus on objects of significance. They also operate independently of the visible light spectrum, and thus work uninhibited by difficult light conditions.

In addition, it can detect motion across a far wider area than thermal cameras even if it does so over a shorter range. Radar comes in at a price well below that of thermal cameras and not far off PIR sensors. More information about the Radar solutions offered by Axis can be found here.

Situation-specific solutions

There are strengths and weaknesses for all of these motion detection solutions, and their effectiveness is dependent the situations in which they are used. A visible light camera would be useless at night on its own, but the addition of a motion sensor-triggered light would vastly improve performance; you probably wouldn’t install an elaborate radar in a 4x4m office; and a PIR sensor would be of little use detecting intruders in a wildlife sanctuary (unless you wanted to detect wildlife).