THOUGHT CENTER > Blog > Alarms

Alarm System Sensor Types

August 8, 2022

What is a security system sensor?

A sensor is a device that’s sensitive to specific kinds of stimuli. Sensors that are part of alarm systems monitor stimuli that represents a safety threat. When a security sensor detects the stimuli it was designed to monitor, it sends an electric signal to the main panel of its alarm system. The electric signal is then converted into a binary code that the security panel reads and uses to trigger an alarm.

Today we’re going to look at some of the major types of sensors that are commonly used by alarm company systems and products.

Motion Sensors

A motion sensor (also known as a motion detector) is a sensor that recognizes the movement of people or objects. There are three main kinds of motion sensor: active microwave motion sensors, passive infrared motion sensors, and hybrid motion sensors.

Active Motion Sensors vs. Passive Motion Sensors

An active motion sensor can detect movement by continuously transmitting electromagnetic radio waves over its field and monitoring for any sudden change or disruption to its radio waves. When a moving object enters the field, the sensor sends an electronic pulse to its control panel, which analyzes the data (to reduce false alarms) before letting the alarm system to go off.

Passive motion sensors are the most common type of sensor in home security systems. Unlike active sensors, passive infrared (PIR) sensors don't beam electromagnetic radio waves over their field. Instead, PIR sensors are able to detect the presence of radiation generated in their field. Because infrared radiation emanates from living people, passive infrared energy sensors are able to detect unwanted visitors by sensing their infrared energy waves.

Motion sensors can be programmed to complete specific actions upon activation aside from initiating alarms and alerting you and your monitoring center service. For example, a motion sensor can be connected with a home security camera so that the camera will begin recording as soon as the sensor detects motion.

Pet-Immune Motion Sensors

Motion detector alarm systems are able to differentiate between humans and pets because most pets are smaller than adults and so create less infrared radiation. Your installer should be familiar with the manufacturer's instructions to make sure your infrared detectors are set to prevent false alarms from pets.

Door and Window Sensors

Alarms for doors and windows come with two main pieces: sensors and magnets. Because the sensor is installed in the frame and the magnet is installed in the part that can be opened, a magnetic field is created between the sensor and magnet for as long as the door or window remains closed. When the door or window opens, the magnet is moved away from the sensor in the frame, breaking the magnetic field and initiating an alarm.

The two main categories of door and window alarm sensors are surface-mounted sensors and recessed sensors. Surface mounted sensors can usually be seen by intruders, which can warn them to take precautionary measures to avoid an alarm response--such as breaking a window for entry rather than raising it. Installation of recessed door and window alarms are therefore encouraged. In a recessed door or window alarm system, holes are drilled into the frame and into the movable part for a more aesthetic and discreet home alarm system.

Glass-Break Sensors

Unfortunately, door and window sensors are only activated if an intruder attempts to raise a window or open a door. If a window is simply smashed, a window sensor will not detect anything. Glass-break sensors fill this blind spot because they're specifically designed to create alerts in the event that an intruder breaks glass.

Acoustic Glass-Break Sensors and Shock Glass-Break Sensors

There are two main kinds of glass-break detectors: acoustic glass-break sensors and shock glass-break sensors.

Acoustic glass-break sensors rely on sound to detect break-ins. Small microphones are set up near windows to recognize sound vibrations that are either above specified frequencies or are in frequencies similar to that of breaking glass. Because an acoustic glass-break sensor has a short range, they require at least one device per room and sometimes even one per window.

Shock glass-break detectors are an alternative to acoustic sensors. They are composed of electrical wires that are placed directly on glass. If an intruder breaks or even rattles glass, a shock glass-break detector will initiate an alarm to let you know what's happening and hopefully to also deter the intruder.

Glass break sensors are often parts of larger home security systems. As such, they can be connected with other devices for a thorough response. For example, a broken window can result in an automatic notification via a security app, the excitement of loud noise throughout the property to deter intruders, the activation of security cameras, and the notification of a professional monitoring service.

Smoke Sensors

There are two main types of smoke sensor: those used in ionization smoke detectors and those used in photoelectric smoke detectors.

Ionization smoke detectors send electrical currents through ionized air. When smoke particles enter the air, the electrical currents are interrupted and the alarm goes off.

Photoelectric smoke detectors use a light beam and light sensor to recognize smoke. The light beam is pointed away from the sensor and under normal circumstances won’t interact with the sensor at all. But in the event of a fire, smoke particles will disperse the beamed light, resulting in some of the light striking the sensor and activating the alarm.

Because Ionization smoke alarms are the best option for detecting fast-burning fires and photoelectric smoke alarms are the best option for detecting slow-burning fires, dual-sensing alarms with both photoelectric and ionization sensors provide superior fire safety coverage.

Carbon Monoxide Detectors

Smoke detectors are designed to warn people of potential fires, but many smoke detectors contain sensors that also recognize deadly levels of carbon monoxide (CO). Carbon monoxide sensors measure the CO in a room. If the CO reaches a dangerous level, the alarm is triggered.

Carbon monoxide (CO) is a deadly, odorless gas and a by-product of burning carbon-based fuel. In the United States alone, at least 430 people accidentally die from carbon monoxide poisoning each year. While the leading cause of these deaths involves CO released by uncontrolled fires, burning fuel in an enclosed space can result in CO poisoning and death. This invisible, scentless gas is produced by many home appliances--including stoves, furnaces, gas and propane heaters, water heaters, lanterns, and even clothes dryers. And because cars produce carbon monoxide, houses with attached garages can build up deadly levels of CO if a car is run while the garage is closed. It’s easy to go to bed with elevated carbon monoxide levels and never wake up.

Luckily, all homes in Connecticut are required to have CO detectors, so you already have one if you’re in CT. However, these detectors have a life expectancy of about seven to ten years. They will begin to beep about twice a minute or display an error signal as they expire. Installation experts at Mammoth Security can check the carbon monoxide sensors in your home, along with your other fire safety equipment, to make sure they're well placed and functioning.

Temperature Sensors

Fire alarms with temperature or heat sensors are the most common type used in restaurant kitchens and industrial environments. This is because smoke from cooking and airborne particles from industrial processes can trigger many false alarms in detectors that rely on smoke sensors. Temperature sensors are also the most reliable fire detection devices, and they can easily be connected with automatic sprinklers and other security system programs.

Fire Alarm Pull Station Sensors

Fire alarm pull station sensors rely on manual movement to be triggered. They are a failsafe option to initiate a fire alarm if smoke or temperature sensors malfunction. A single-action alarm box can trigger an alarm the moment its handle is pulled down. A dual-action pull station requires at least two actions to trigger an alarm. For example, a glass shield may need to be broken before the alarm can be pulled.

Alarm Systems and Their Sensors

Security alarm systems use sensors to detect stimuli that represents a safety threat. They are designed to alert people to threats such as intruders, dangerous levels of carbon monoxide, and fire. There are several different possible detection methods for any threat and each type of alarm has a sensor that reacts to a specific symptom of danger.





I’m not just another sales guy. I’m a security expert ready to discuss your security strategy one-on-one.

Let’s discuss your security strategy and get you a tailored solution that will perfectly fit your security expectations.

Get your FREE copy of ‘Top 10 Questions to Ask Before Purchasing A Camera System’