Pyrometers & IR-Thermometers
Pyrometers
Fixed, Non-Contact Temperature Measurement
Principle
Pyrometers measure temperature by detecting infrared (IR) radiation emitted from an object. The intensity of this IR radiation increases with the temperature of the emitting object. Since all objects emit some level of IR radiation, pyrometers use specialised lenses to focus on a small “spot” and determine the temperature. They are available in both fixed and hand-held models.
Advantages
- No physical contact with the process
- Can average the temperature across large areas rather than at single points
- Wide range of temperature measurement capabilities
Disadvantages
- Susceptible to interference from dust, smoke, haze, or other optical obstructions
- More expensive compared to contact sensors
Focus
When selecting a sensor, consider the target size you want to measure. Pyrometers have a specific “spot size” at a particular range, the area measured by the sensor. This spot size increases as the distance from the pyrometer’s focal point increases.
Emissivity
Different materials emit and absorb IR radiation differently, with some being more reflective, meaning they not only emit their own IR radiation but also reflect IR radiation from other sources. For example, a perfect black body has an emissivity of 1, meaning all the infrared emitted is from the object itself. In contrast, polished metals like copper have low emissivity, making them difficult to measure without specialised pyrometers designed for such surfaces.
Thermal Imaging
Beyond the Basics
Principle
Thermal imaging cameras function like digital cameras but are sensitive to infrared rather than visible light. They capture temperature data of objects in the field of view. Available in both hand-held and fixed mounting versions, thermal imaging cameras have become more affordable with the advent of low-resolution models.
Advantages
- No contact with the process
- Can drastically reduce inspection time by providing a comprehensive view of the system from a distance
Uses
Thermal imaging cameras are invaluable for mechanical and electrical engineers in fault-finding and preventative maintenance. They allow for quick identification of hot or cold spots, saving hours of manual temperature checking. Builders and inspectors use them to detect issues like insect activity, rising damp, water damage, and mildew. They are also useful for security applications, detecting human presence in low-light conditions.
Features
Thermal imaging cameras can display the highest, lowest, or average temperatures across the image, and generate detailed reports that can be printed or stored digitally. Fixed units can trigger alarms if temperatures exceed set thresholds, making them ideal for machine protection and fire detection.