The In-Depth Guide to Security Sensors

Quick definition: Security sensors are devices that detect glass breaking or unauthorized entry and motion and trigger alerts in a home security system.

Three main security sensor types:

• Door/window sensors: Detect when doors or windows open. Most commonly uses a contact sensor and a magnet.
• Motion sensors: Identify movement in your home. Most commonly uses infrared technology.
• Glass break sensors. Recognize and alert to the sound or vibration or breaking glass.

If you’re like many people, when you think of a security system, you think of alarms.

That’s because most systems are designed to sound an alarm that alerts you to the presence of danger or unauthorized people in your home. But how does your security system know when a threat is detected? The answer is security sensors. 

Security sensors are one of the most important components of your home security system. Without them, you wouldn’t have the alarms needed to alert you to danger.

This guide will go over the different types of security sensors a home needs, how they work, and where to put them.

Do I need security sensors for my home?

No home security system is complete without a range of security sensors. These smart sensors provide many different benefits, including:

• Alerting to unauthorized access. Perhaps the most important feature of a security sensor is to alert you and your security system’s professional monitoring center that someone has entered your home. From there, you can take action to get your family to safety.
• Scaring away potential threats. Some intruders think yard security signs are just a scare tactic and will try and break into your home anyway. But once an intruder alarm is tripped, that alone is often enough to scare away a potential burglar.
• Lets you know when a door is open. Security sensors are important for parents, too. If you have a child who’s a master escape artist, security sensors can let you know when an exterior door is opened.
• Helps alert caretakers. If you’re a caretaker for an adult with dementia who is prone to wandering, a door alarm can help prevent a dangerous situation.
• Alerts you to broken glass or open doors. Not every broken glass or open door is the result of something ominous like a break-in. Security sensors can also alert you to something like a broken window from a stray ball or a door blown open during a bad storm.

Each different type of security sensor, from door alarms to motion sensors to glass break detectors, plays an important role in the overall safety of your home and family.

Door and window alarms

Door and window alarms are an essential part of any home security system, triggering your alarm when a door or window in your home is opened. If your alarms are part of a professionally monitored security system, they will also alert the monitoring center.

Types of alarms

All door and window alarms basically do the same thing: they tell your security system whether a door or window is open or closed. Depending on your security system and its settings, this may result in a simple notification beep when your alarm isn’t set, or trigger your much-louder security alarm when your system is set.

Door and window sensors are either wired or wireless. Hardwired sensors are often professionally installed, communicating to your security system’s panel via the hardwire connection. Wireless sensors, on the other hand, communicate via radio frequency to your panel.

These alarms can further be classified by the different types of doors and the ways they are placed or installed:

• Recessed sensors are installed inside the windows or doors themselves. These provide a hidden, seamless look, but typically require professional installation.
• Surface-mounted sensors are mounted directly on the door or window. This makes them easier to be moved as needed.

Whether you get hardwired or wireless, recessed or surface-mounted depends on your individual needs. Hardwired don’t require batteries, but they don’t have the same flexibility as a wireless sensor that can be moved. Recessed may look neater, but they are more complicated to install. Keep these things in mind as you determine the best fit for your home.

How do door and window alarms work?

Door and window sensors work by using a magnet and contact sensor that triggers an alarm when their connection is broken.

Door and window alarms use two main parts—a contact sensor and magnet—to tell whether your door or window is open or closed. One of the contacts is placed on the stationary part of the door or window, like the frame or wall. The magnet is installed on the moving part. When the contact is broken, the door sensors send a signal to the panel, and the alarm is triggered.

Where should I put door and window sensors?

One question many people have is, “Do I really need sensors on every door and window?” This depends on what you want your system to do.

If you want to prevent break-ins, it’s helpful to know how the average intruder accesses a home:

Break-in entry points at a glance:

• 34% through the front door
• 22% through the back door
• 23% through first-floor windows
• 9% through the garage door

Key takeaway: 88% of break-ins occur through first-floor entry points. Prioritize sensors on all ground-level doors and windows.

With that in mind, it’s a good idea to put a sensor on every first floor door or window.

If your second story windows are easily accessed via a porch or tree, you might also consider adding window sensors in that area.

Motion sensors

Motion sensors are small devices that are mounted on the wall or ceiling. When your security system is armed and movement is detected in the sensor’s field of vision, the motion sensor activates the alarm.

How do motion sensors work?

Motion sensors are sensors that detect motion, which then triggers an action. Motion sensors are used to turn lights on, activate recording on security cameras, and set off burglar alarms, to name a few.

When it comes to the technology used to activate a motion sensor, there are several different types. Each type works in a different way. Some of the most common include:

• Passive Infrared motion sensors (PIR): Used in approximately 90% of residential security motion sensors, PIR sensors detect body heat in their field of vision. This is used to detect people, animals, and other warm, moving objects.
• Microwave motion sensors: This type of sensor constantly sends out microwave pulses to a defined area, then measures the amount of time it takes the waves that bounce back. If a person or object interferes with the signal, it delays the return time, setting off the alarm.
• Dual-technology motion sensors: Typically consisting of both microwave and PIR sensors, dual-technology attempts to reduce false alarms because both sensors must go off to trigger the false alarm.

Motion sensor comparison

There are pros and cons to each type. PIR sensors, for example, are sophisticated enough to ignore things under a specified weight, which can help minimize false alarms from pets. Microwave sensors are good for irregularly shaped or large areas, but they can be quite costly. Dual-technology motion sensors would work well for businesses, but may be overkill for a home.

For the majority of home alarm systems, PIR technology will be sufficient.

Where should I place motion sensors?

Placement is key to making sure your motion sensors are effective. These tips can help ensure you place them in the most effective areas:

• Know your motion sensor’s range. Check the manufacturer’s guide if you’re unsure.
• Place motion sensors higher up on the wall, so they can cover a large amount of area
• Consider putting them in high-traffic or high-value areas, such as a hallway or master bedroom
• Be aware of tall furniture or other objects that can block a motion sensor’s field of view
• Avoid placing motion sensors near sunny windows, which can interfere with its ability to detect heat
• Consider things like curtains or fans, which can blow in front of the sensor and trigger a false alarm
• Use corners when possible; these are good spots for motion sensors and can catch motion from a wide field

If you’re unsure of the best place to install your motion sensors, you can consult with your security home provider. Vivint, for example, includes professional installation with all security systems, so their technicians can advise on the best places throughout your home to put your motion sensors.

Glass break sensors

While locking your doors and windows can be an effective deterrent for many burglars, some are much more brazen and will break a window in your home to gain access.

That’s where glass break sensors come in.

What are glass break sensors and how do they work?

Glass break sensors are small sensors placed on windows or glass doors or within a specific radius. There are two main kinds:

• Acoustic glass break sensors. Broken glass emits a specific sound frequency. An acoustic glass break sensor can “hear” when glass is broken by picking up on the frequency it makes.
• Shock glass break sensors. This type must be placed on the glass itself because it senses the vibration that occurs when glass is broken.

Acoustic glass break sensors are preferable in home security settings, mostly because they can cover a wider range of glass than a shock sensor.

Once the glass break sensor goes off, the sensor then triggers your burglar alarm, alerting you and your monitoring company that a window has been broken.

Why do I need glass break sensors?

If you have motion sensors and door and window sensors, do you really need glass break sensors? Definitely! Glass break sensors are part of a well-rounded, comprehensive home security system and provide additional protection.

For example, as we discussed earlier, window sensors are activated when contact between the two sensors is broken. If the glass in the window is broken, the contact sensors remain intact, so the break wouldn’t trigger your security alarm.

How many glass break sensors do I need?

If you’re using shock glass break sensors, you will probably want one for each ground floor window to provide the best coverage. Most home glass break acoustic sensors have a working radius of 15–25 feet, so placing one in the middle of a room with multiple windows should be sufficient.

When in doubt, you should consult with your security provider for their recommendations.

Security sensors–the bottom line

At the end of the day, your security sensors should provide you with peace of mind. With sensors that cover situations that are most likely to occur, whether it’s a broken pane of glass or an intruder breaking into your home, you’ll know that your home is being protected no matter what comes your way.

Let Vivint help you secure your home with the smart security sensors you need to keep your home and family safe. Each Vivint system is customized to your home’s unique needs. Contact our Smart Home Pros today for a free consultation at 855.822.1220.

Frequently asked security sensor questions

Door & window, glass break, and motion sensors are all designed to keep your home safe.

Do I need sensors on every window?

Prioritize first-floor doors and windows as 88% of break-ins happen through ground-level entry points. Add sensors to upper-floor windows if they're easily accessible.

How many glass break sensors do I need?

If your glass break sensor is a shock sensor, one per window pane provides coverage. For acoustic sensors, one per room with windows may be sufficient since they cover a 15–25 foot radius.

What's the difference between wired and wireless sensors?

Wired sensors connect directly to your home's wiring and do not require batteries. They are harder to move, unlike their wireless counterparts which offer flexible placement. Wireless sensors use radio frequency to communicate but do require periodic battery replacement.

What's the best motion sensor for homes with pets?

PIR (Passive Infrared) sensors work well for pet owners because they can be set to only respond to movement from beings over a certain weight.