How Do Infrared Temperature Sensors Work?
Infrared temperature sensors, also known as infrared thermometers or pyrometers, are devices designed to measure the temperature of an object without direct contact.
These sensors utilize the principles of infrared radiation and the relationship between temperature and the emitted infrared radiation to provide accurate temperature readings.
The key components of infrared temperature sensors include a lens, a detector, and an electronic processing unit.
1. Infrared Radiation
All objects with a temperature above absolute zero emit infrared radiation. This radiation is a form of electromagnetic radiation with wavelengths longer than visible light.
The amount and characteristics of the emitted infrared radiation depend on the object’s temperature.
Infrared temperature sensors leverage this principle to measure the temperature of an object by detecting and analyzing its infrared radiation.
2. Two Types of Infrared Temperature Sensors:
- Contact Infrared Temperature Sensors (IRTs): These sensors are designed to be in direct contact with the object whose temperature is being measured. They typically feature a probe or a thermopile that directly touches the surface. Contact IRTs are suitable for situations where physical contact is feasible and are commonly used in applications such as food processing, industrial machinery, and scientific research.
- Non-contact Infrared Temperature Sensors (NCIRTs): NCIRTs, also known as infrared thermometers, are the more common type. They measure the temperature of an object without physically touching it. These sensors are suitable for measuring the temperature of moving objects, hazardous substances, or situations where maintaining a distance is crucial. Non-contact infrared temperature sensors are widely used in various industries, including manufacturing, automotive, and healthcare.
3. Optics and Lens System
The lens of an infrared temperature sensor plays a crucial role in focusing the infrared radiation onto the sensor’s detector.
The lens is designed to allow only the infrared radiation emitted by the target object to pass through and reach the detector. The optics of the sensor are carefully calibrated to ensure accurate and reliable measurements.
The detector is a critical component that captures and converts the incoming infrared radiation into an electrical signal.
Different types of detectors are used in infrared temperature sensors, including thermocouples, bolometers, and pyroelectric detectors. The choice of detector depends on factors such as the required temperature range, response time, and sensitivity.
- Thermocouples: These detectors generate a voltage in response to temperature changes. The voltage produced is proportional to the temperature of the object being measured.
- Bolometers: Bolometers are devices that change their electrical resistance based on temperature variations. The change in resistance is measured to determine the object’s temperature.
- Pyroelectric Detectors: Pyroelectric materials generate an electric charge in response to changes in temperature. The charge is measured to determine the temperature of the target object.
5. Electronic Processing Unit
The electronic processing unit of an infrared temperature sensor is responsible for converting the electrical signal from the detector into a temperature reading.
This unit often includes a microprocessor and algorithms that take into account the sensor’s calibration, emissivity adjustments, and other factors affecting the accuracy of the measurement.
6. Emissivity Adjustment
Emissivity is a measure of how efficiently an object emits infrared radiation compared to a perfect emitter (a blackbody).
Since real-world objects do not always behave like perfect emitters, infrared temperature sensors often allow users to adjust the emissivity setting to match the material properties of the object being measured.
This adjustment ensures more accurate temperature readings.
7. Distance and Spot Size Ratio
Infrared temperature sensors have a specific distance-to-spot size ratio, indicating the size of the measurement area at a given distance.
This ratio is crucial for obtaining accurate readings, especially when measuring the temperature of small or distant objects.
The choice between contact and non-contact infrared temperature sensors depends on the specific requirements of the application.
Non-contact sensors are favored for their versatility, speed, and ability to measure temperatures from a distance, while contact sensors are preferred when direct contact is permissible or necessary for accurate readings.