Single-Wavelength Pyrometer Technology
There are three distinct technologies for Single-Wavelength pyrometers: Short-Wavelength, Long-Wavelength, and Specialty-Wavelength. Single-Wavelength pyrometers are preferred when appropriate due to simpler, lower-cost technology. For most applications, select the shortest wavelength compatible with the measurement conditions and desired temperature span. Specialty wavelengths may be necessary depending on the optical and emissivity properties of the target.
Williamson places a strong emphasis on short-wavelength single-wavelength pyrometers because of their ability to better tolerate emissivity variation and optical obstruction. As a result, Williamson short-wavelength pyrometers provide superior performance over a wide range of real-world operating conditions.
Short-Wavelengths Reduce Error from Emissivity Variations
For most applications, selecting the shortest practical wavelength is recommended. As indicated in the chart, shorter wavelengths result in smaller errors. In fact, short-wavelength sensors can be 4-20 times less sensitive to emissivity variation compared to long-wavelength sensors.
Short-Wavelengths Can View Through Optical Obstructions
Wavelength selection is a critical factor in Williamson’s short-wavelength technology. By choosing the correct wavelength span, you can view through water, steam, flames, combustion gases, plasmas and other common industrial interferences.
Long-Wavelength (LW) pyrometers tend to be lower in cost, but when measuring temperatures above 100˚C / 200˚F, errors can be large due to optical obstructions, misalignment, and emissivity variations. These are general purpose sensors used for many low-temperature or near ambient measurements and high emissivity materials.
Specialty-wavelength pyrometers are used when the target is least reflective and most opaque at a specific wavelength or when optical obstructions are most transparent at a specific wavelength.
Example: Emission band for polyester film
At 7.9µm, polyester film is opaque. Pyrometers filtered at this special wavelength are appropriate for making this measurement.
Each Specialty-Wavelength pyrometer is designed for a specific application. Download the datasheet to determine which wavelength is appropriate for your application.