【正文】 。s calibration equation and the target39。s emissivity, that indicates an object39。F, the smart sensor, or series of sensors, can be calibrated to that temperature. ? Twopoint. If sensor readings must match at two specific temperatures, the twopoint calibration shown in Figure 3 should be selected. This technique uses the calibration temperatures to calculate a gain and an offset that are applied to all temperatures throughout the entire range. ? Threepoint with variable temperature. If the process has a wide range of temperatures, and sensor readings need to match at three specific temperatures, the best choice is threepoint variable temperature calibration (see Figure 4). This technique uses the calibration temperatures to calculate two gains and two offsets. The first gain and offset are applied to all temperatures below a midpoint temperature, and the second set to all temperatures above the midpoint. Threepoint calibration is less mon than one and twopoint, but occasionally manufacturers need to perform this technique to meet specific standards. Field calibration software also allows routine diagnostics, including power supply voltage and relay tests, to be run on smart sensors. The results let process engineers know if the sensors are performing at their optimum and make any necessary troubleshooting easier. Conclusion The new generation of smart IR temperature sensors allows process engineers to keep up with changes brought on by newer manufacturing techniques and increases in production. They now can configure as many sensors as necessary for their specific process control needs and extend the life of those sensors far beyond that of earlier, “nonsmart” designs. As production rates increase, equipment downtime must decrease. By being able to monitor equipment and finetune temperature variables without shutting down a process, engineers can keep the process efficient and the product quality high. A smart IR sensor’s digital processing ponents and munications capabilities provide a level of flexibility, safety, and ease of use not achieved until now. How Infrared Temperature Sensors Work Infrared (IR) radiation is part of the electromagic spectrum, which includes radio waves, microwaves, visible light, and ultraviolet light, as well as gamma rays and Xrays. The IRrange falls between the visible portion of the spectrum and radio waves. IR wavelengths are usually expressed in microns, with the IR spectrum extending from to 1000 microns. Only the micron band is used for IR temperature measurement. Using advanced optic systems and detectors, noncontact IR thermometers can focus on nearly any portion or portions of the micron band. Because every object (with the exception of a blackbody) emits an optimum amount of IR energy at a specific point along the IR band, each process may require unique sensor models with specific optics and detector types. For example, a sensor with a narrow spectral range centered at microns is optimized for measuring the surface temperature of polyethylene and related materials. A sensor set up for 5 microns is used to measure glass surfaces. A 1 micron sensor is used for metals and foils. The broader spectral ranges are used to measure lower temperature surfaces, such as paper, board, poly, and foil posites. The intensity of an object39。 peakhold returns an object’s peak temperature either over a period of time or by an external trigger. ? HI alarm/LO alarm can be set to warn of improper changes in temperature. On some process lines, this could be triggered by a break in a product or by malfunctioning heater or cooler elements. ? Attenuation indicates alarm and shut down settings for twocolor ratio smart sensors. In this example, if the lens is 95% obscured, an alarm warns that the temperature re