Avancerad teknik för mätning av infraröd temperatur

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 are 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. For example, at 7.9um polyester film is opaque. So pyrometers filtered at this special wavelength are appropriate for making this measurement.

MW Pyrometers provide consistent and accurate measurements with non-greybody materials under a wide range of operating conditions without any adjustments. The MW pyrometers use application specific ESP Algorithms to accurately correct for emissivity variations due to:

• Changes in alloy, surface texture, surface oxidation
• Abnormal operating conditions such as a furnace leak, bad roll, or reheated coil (Annealing Line)



The most common applications involve aluminum, steel, and copper. Each MW pyrometer can hold up to eight selectable algorithms so that the same sensor can be used for multiple applications.

The MWx pyrometers work differently than traditional MW technology which assumes that the surface conditions are relatively consistent. The MWx sensors use Dynamic ESP Technology to automatically compensate for more significant variation in surface character and conditions without any adjustments. The two applications which require the more advanced MWx technology are:



• Aluminum hot rolling mills where the surface character of the aluminum varies dramatically by alloy and pass as it goes through the reversing mill.
• High temperature (<900°F/480°C) aluminum billets where there is an elemental migration of aluminum to the outside billet surface that dramatically changes the emissivity of the billet surface.
  

Two-color pyrometers use what is called a “sandwich detector” using a fixed set of wavelengths, meaning that two wavelength filters are laid one on top of the other. One wavelength is a broad waveband (0.7-1.1um for example) and the other wavelength is a narrow waveband (1.0-1.1) that is a subset of the broader band.

• General purpose wavelength set
• Can tolerate modest optical obstructions, misalignment and partial field of view
• Compensate for variable emissivity
• Used when there is a clear optical path between the pyrometer and target
• Can only measure temperatures above 1100°F / 600°C

Keep in mind that two-color pyrometers cannot view through common optical interferences, so it is critical to avoid water, steam, flames, combustion gasses, plasma and laser energy for the most accurate and repeatable results.

Dual-wavelength pyrometers use two separate and distinct wavelength sets on a filter wheel. Because the design allows for separate wavelengths, these wavelength sets can be independently selected and combined allowing for some unique capabilities.

• Compensate for variable emissivity, temperature gradients, severe optical obstructions, and misalignment
• Select wavelength sets tolerate water, steam, flames, combustion gasses, plasma, and laser energy
• Separation of wavelengths produces a heavily weighted reading towards the hottest temperature viewed
• Available in broad temperature spans and low-temperature ranges
• Includes ESP filtering to continuously measure intermittent targets or eliminate intermittent interferences

Dual-wavelength pyrometers offer two different and selectable wavelengths allowing for all of the benefits of a two-color pyrometer plus some additional capabilities.