Microwave Vs Infrared Activation Sensors – What’s the Difference?

When it comes to automatic door sensors, there are two primary options that you can choose from: microwave sensors and infrared sensors.  But what exactly is the difference between these two sensors? And which would make a better door sensor?

These two types of motion sensors are the most common ones you’ll find in commercial buildings, and it’s not hard to figure out why – both work efficiently at detecting moving people and objects, and immediately opening automatic doors.

To answer these questions, let us first break down how each one works.

The Infrared Sensor

The infrared sensor works by measuring the infrared light radiating from the objects in its field of view. All objects with a temperature above absolute zero emit heat energy in the form of radiation. The human eye cannot see this radiation, but electronic devices like the infrared sensor can detect it.

The infrared sensor conducts an analysis of a room or surrounding areas, and looks for a change in infrared energy. Should it detect a change, such as the presence of a moving person in the proximity, it will emit a pulse activating the automatic door sensors, which in turn prompts the doors to open.

Infrared sensors are also known as Passive Infrared Sensors. “Passive” means these sensors emit no energy; they simply detect infrared radiation that objects emit or reflect. Touchless switches such as the SafePass J-Wave also use active infrared. This slim jamb-style switch suits hygiene-critical areas.

The Microwave Sensor

The microwave movement sensor works quite differently to the infrared sensor. It applies the Doppler effect in that it sends out microwave signals and measures the length of time it takes for these signals to bounce off of surrounding objects and return to it. This echo time is what it uses to calculate the distance of stationary objects around it. It first establishes a baseline room or area analysis to detect the current distance of all surrounding objects. When something enters the detection area, it interrupts the microwave signals and changes the echo time, which triggers the sensor.

The microwave sensor works much like a RADAR or SONAR system, sending out signals to measure its distance from objects. But the microwave sensor can also detect motion through wood, plastic, glass and most other construction materials except metal. Metal acts as a shield, creating dead zones behind them. This can be both an advantage and disadvantage to the microwave sensor. Touchless switches like the SafePass ClearWave also use microwave technology. A simple hand wave activates the door, which suits hygiene-sensitive areas such as hospitals and food processing.

Microwave detection suits large or irregularly shaped entrances, as it provides a wide detection area and performs reliably across extreme temperatures. You can also set many microwave sensors to respond to movement in one direction only, which reduces false activations and stops doors staying open longer than necessary

Now that we know what the difference is between the two, it’s time to answer the question: which is better? However, there is no clear-cut answer:

Comparison

• Microwave sensors are highly sensitive and are able to detect motion even through thin walls. In this sense, they are more powerful than infrared sensors. But their sensitivity means they can easily trigger false alarms. They sense movement by speed and size, so trees blowing in the wind, moving drapery or movement beyond walls can set them off, even though these shouldn’t trigger a sensor. Even fluorescent lighting, which emits detectable light particles, can activate the sensor and trigger it.

• Infrared sensors on the other hand, are less prone to such false alarms. Because they detect movement through heat and light, ambient temperature can affect their performance. High temperatures above 35℃ often reduce their sensitivity. The opposite happens in very cold temperatures wherein they become extremely sensitive. Microwave sensors are more stable in this sense, operating properly even at temperatures as low as -20℃ and as high as 45℃.

• Since infrared sensors detect movement through body heat – they are ideal for situations that require defined detection, such as in front of a doorway or down a walkway. But they must be installed in just the right position to provide effective coverage.

• Microwave sensors are great for just about any environment. They can provide fine motion-sensing whether in high heat, a large indoor commercial area, or large outdoor area that may be awkwardly shaped. This makes them one of the most versatile of sensors. For large industrial doors, the SafePass HR-Robus is a rugged, high-mount microwave sensor that detects fast-moving vehicles from up to 7m.

• Microwave sensors often have a longer lifespan than infrared sensors. They’re also one of the oldest and most relied on sensor technologies, but can be more expensive to run since they require more power.

• Since microwave sensors work at intervals – meaning they first emit signals and then receive them- it’s possible that someone or something moving fast enough may not be detected.

Why Fit Door Activation Sensors?

Door activation sensors make your entrance welcoming, efficient and secure. They open and close automatic doors as people approach, keep them locked after hours, and help reduce energy use, maintenance costs and accessibility barriers.

1. Easier entrance and exit monitoring

Door sensors make it easier to monitor who comes and goes. Because a person must be within the detection area to open the door, everyone is guaranteed to pause at the entry point, where CCTV can clearly capture them.

2. Remote control

Many automatic door sensors have remote controls, which allow you to conveniently set sensor parameters remotely.

3. Energy savings

Automatic door sensors can actually lower your energy costs. Heating and cooling are usually a building’s biggest energy use, and doors left open make them work harder. Sensors keep doors open only when needed, preserving indoor temperature. Many also use very little power themselves, and some can tell pedestrians from vehicles and open only as wide as required.

4. Easy entrance and exit for materials and supplies

If your business or facility often receives large deliveries of materials and supplies; or if your business needs to move goods in bulk regularly, door activation sensors are essential. These will allow easy entrance and exit of large, bulky items.

5. Easy entrance for people with disabilities

This is especially necessary for hospitals and other medical facilities where persons are wheeled in on wheelchairs and stretchers, or have disabilities and require assistance when going through doors. Door activation sensors make it so that these people don’t need to exert any effort to go through doors.

6. Lesser maintenance and assorted costs

Because doors or access points need not be touched when door activation sensors are present, damage to doors or sensors due to pedestrian use or direct contact is minimised or even eliminated. This means you spend less time and money on maintenance, and they last longer than most other types of entry systems.

So which sensor would be better for your automatic door? Generally, infrared sensors such as the HR100-CT suit compact, well-controlled entryways, whereas microwave sensors such as the HR50 suit larger or more varied entrances, including swing doors. But who says you need to choose anyway? Dual-technology sensors like the SafePass SSR-3 give you both.

With Rotech’s selection of commercial automatic door sensors, you can get both infrared and microwave technology in one! We also have a great selection of microwave only and infrared only door sensors. Take a look at our product range today or contact us for tailored advice.