Pictured is a method for testing high temperature measurements by comparing the color spectrum of light at various power settings with an Optical Pyrometer. The devices are calibrated at NIST. The power through the bulb is varied and monitored by the meter on the table. The scanning device that the technician is looking though is adjusted till the color scheme viewed within in the device matches the color of the emanating from the bulb at the particular power setting. Using a relationship table provided, the technicians can then identify the temperature.The light source pictured is used to calibrate the device that the technician looks through. The technician would then go to a source of heat such as an oven and by aligning the color given off by the unit under test (UUT), he would use the reference table to determine the sources heat output.