In our last post, Brett explained why LumaSense is exploring innovations that wed the well-known arena of pyrometry with thermal infrared (IR) imaging. Emerging from our customer-driven R&D efforts is a new area of temperature measurement and control—a potentially transformative technology that we call Rel-Rad™.
To understand why Rel-Rad is so transformative, I thought it would be useful to take a brief snapshot of the current state of pyrometry and thermal imaging and explain where Rel-Rad fits.
Essentially, everything we know emits electromagnetic radiation—you, me, even the walls around us. This radiation arises from the thermal motion of molecules within an object, and is generally peaked in the near infrared (IR) region of the electromagnetic spectrum (0.7 – 20 um), which is invisible to the human eye. As temperatures increase, the peak emissions move into the visible range; think blacksmith forming a horseshoe. Pyrometers and thermal Imagers are instruments that can remotely detect an object’s emitted electromagnetic radiation and convert this signal into a temperature reading.
The study of material’s thermal emissions and IR thermography was developed during the mid-1800’s and culminates with the Planck spectrum, which defines the spectral radiation for an ideal ‘black body’ that emits the maximum radiation at a given temperature. We can then use the shape of this spectrum along with specially designed cavities that approach an ideal black body to perform a ‘radiometric’ calibration of a pyrometer or thermal imager. With a little care, the resulting calibrated system can then be used to provide accurate temperature readings for a variety of applications.
IR thermography has developed something of a mysterious aura, stemming from the false perception that the technology is difficult to master. In truth, it is a direct and precise means of temperature measurement that is really fairly simple. Point and shoot, so to speak. The trick is understanding the radiation emission (‘emittance’ or ‘emissivity’) and reflectivity properties of the object to be measured and then selecting a corresponding pyrometer or thermal imager that is sensitive in the spectral range where the emissivity is high. Of course there are a host of other concerns that are application and environmental specific, but the material properties are generally where the black magic is addressed.
Pyrometers and thermal imagers both have the same basic operation and concerns when selecting the proper device. A pyrometer will accurately measure the temperature at a single point on your object, the size of which is determined by the optics selected and distance to the object. These devices are plentiful, and generally quite cost effective. Thermal Imagers are the logical extension of wishing to measure the temperature of multiple points, without buying a boat load of pyrometers. Imagers typically have a detector array with over 100,000 pixels, each of which can measure the temperature of a single point, and together form a 2-dimensional image the size of which is again determined by the optics selected. Rather than display a 2-D array of numbers to represent the measured temperatures, thermal imagers overlay a color palette with each color representing a temperature, to produce visually stunning images. This process requires full radiometric calibration of each pixel to insure accurate temperatures & colors. However, the cost of a fully radiometric IR camera often ranges well beyond the budgets of cost-sensitive manufacturing operations.Pyrometry is actually quite simple. The concepts of electromagnetic emissivity of base materials – canonically known as blackbody radiation – were originally defined in the mid-1800’s by Max Planck and other scientists of the day.
To sum it up: Pyrometry gives you a highly accurate reading for a single point in a very low-cost package vs. radiometric thermal imaging, where you can get a number of readings to make a thermal image, but the cost is much higher.
Today, pyrometry and thermal imagery are widely used in most every segment of industrial materials and advanced technology manufacturing and processing. Thermal imagers certainly are the preferred solution for some applications, but recall the emissivity issue I spoke of above: If an image from a complicated object or scene is not corrected for emissivity pixel by pixel then the colors you see will not represent the true temperature. You may be paying for a calibration that is not needed!
So where’s the happy medium?
Enter Rel-Rad, combining low-cost spot pyrometry with lower-cost non-radiometric IR cameras to produce thermal images that are relatively radiometric. In Rel-Rad, the pyrometer delivers a precise temperature point, while the camera shows the variation across the surface. Together, Rel-Rad delivers relatively radiometric infrared imaging at a significantly lower cost than fully radiometric imagers.
- Now that we understand why Rel-Rad is so transformative, how do you see pyrometry and thermal imaging helping you transform your own industrial landscape?
- How would an image help you where you measure a temperature point today?
- Where are you not measuring temperature that might help you?
Want to test a Rel-Rad solution for your industrial application? Contact LumaSense Application Engineering at firstname.lastname@example.org.
If you’d like a copy of the LumaSense Infrared Thermometer Handbook, email us at email@example.com, and we’ll be happy to send it to you.
Our guest blogger is LumaSense Director of Global Applications. With a Ph.D. in Physics from the University of Iowa, Dr. Tim Dubbs has 20+ years of experience in sensors and system development.