Testing Temperature Uniformity on a Flat-Plate Infrared Calibrator

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Testing Temperature Uniformity on a Flat-Plate Infrared Calibrator (99.41 KB)

There are a number of instruments used to perform infrared (IR) thermometer and IR imager calibration. These instruments fall into two categories, cavities and flat-plates. To calculate the uncertainty in using these instruments, the temperature uniformity must be known. This is especially true with flat-plates. This uncertainty may be given in an instrument’s specification. However, there is not a standardized test method to test the uniformity of a flat-plate calibrator as there is with other classes of temperature calibrators such as dry block calibrators.

What compounds this problem is that a uniformity specification may mean something different for the IR imager user than it does for the IR thermometer user. This is because an IR thermometer measures the radiation emitted by a sizable area of the calibration surface. In effect, the IR thermometer averages the temperature over this area. By contrast, the IR imager measures many areas that are much smaller. This type of measurement approaches a point temperature measurement.

This paper discusses how uniformity is measured by a flat-plate manufacturer. It discusses what this means for both the calibration of an IR imager and the user of an IR thermometer. It then proposes a test method that may become a standard for testing flat-plates. This paper should be of interest to anybody who calibrates or tests either IR imagers or IR thermometers.