Infrared (IR) sensors, such as Process Parameters temperature probes, are devices used to detect and measure infrared radiation. Infrared sensors are categorized into two: passive and active. We will discuss the two types of IR sensors, their applications, and their benefits.
Types of Infrared Sensors
Active Infrared Sensors
Active infrared sensors detect and emit infrared radiation. Infrared detectors and infrared sources are employed in this type of infrared sensor. Laser diodes or light-emitting diodes are the sources of transmitting energy for the sensor to operate. An imaging active IR detector uses a laser diode, whereas a non-imaging active IR detector uses an LED. The energy reflected after the target is illuminated by the laser diode or LED is concentrated on the detector. To get the desired information, signal processing algorithms are used to process the measured data.
During day and night operation, presence, occupancy, speed, and count data are provided by the active IR detectors. Because the shape and target profile data are provided, target classification can be done using laser diode type. They can be used as reflective Opto sensors.
They are two configurations used in the reflective Opto-sensors, which are:
- Break beam Sensors – consist of light-detecting and light-emitting elements. An electronic fence is created when the source produces infrared radiation toward the receiver. An action is taken by the electronic circuitry after an electronic wall is made due to objects being opaque, thus changing the output.
- Reflectance sensors – This type of sensor is built in a single housing consisting of an IR detector and IR source. Because of that reason, the infrared radiation reflects when an external object blocks it. The object’s surface determines the amount of light reflected.
Passive Infrared Sensors
Passive infrared sensors only contain IR detectors, thus forming the majority of IR detectors/sensors classes. Count, occupancy, and presence are the measurables that passive infrared sensors can detect. This type of sensor does not emit infrared energy; therefore, it detects the emitted energy by other objects in the surrounding. To achieve the desired information, a signal processing algorithm may be used.
Passive infrared sensors are categorized into two types
- Thermal IR sensors – This type gets its heat from infrared energy. Because it does not have wavelength dependency, it contains independent photosensitivity. The detection time and response time of thermal IR sensors are slow even though cooling is not required. Some common types of thermal IR sensors include; thermocouples, bolometers, and pyroelectric detectors.
- Quantum IR sensors – This type of sensor depends on the wavelength for photosensitivity; thus, the response speed and detection are higher and faster. There is a need for cooling to achieve accurate and desirable measurements. It is divided into categories namely, Intrinsic and Extrinsic types.
Application of IR Sensors
- Radiation thermometers
- Flame monitors are used for flame detection and determining how the flame is burning.
- Moisture analyzers – They are used to detect infrared energy by analyzing the wavelength in the moisture regions.
- Gas Analyzers – are used to measure the gas density by using gas absorption characteristics. They are of two types; Dispersive and Nondispersive.
- IR imaging devices – are used in thermal images, night vision devices, and many others because they are not visible.
- Remote sensing – gives information on an object by measuring the wavelength of light emitted by the object.
- Missile guidance – is used to give direction to the missile using the passive infrared guidance system.
- Optical power meters – measure optical fiber transmission loss, light intensity, laser power, and many more.
- Sorting devices – They are used to sort agricultural crops from clods and stones by the inherent property of absorption.
- Human body detection – They are used for detecting the presence of a person, such as auto light switching.
- Spectrophotometers
- LD monitors
Benefits of IR Sensors
They are various benefits that come along with infrared sensors. They include:
- Simple circuitry thus requires low coding/decoding
- Low power consumption
- High noise immunity
- Beam directionality; thus, the data is not spilled or leaked
- International regulatory constraints are few
