Calibration and Measurement Procedures for a High Magnification Thermal Camera

Infrared thermography is a relatively mature measurement technology, however systematic evaluation of measurement uncertainty for multi-point measurement (an infrared focal plane array) is very limited, or, does not follow uncertainty evaluation guidelines outlined in the Bureau International des Poids et Mesures Guide to the Expression of Uncertainty in Measurement (BIPM-GUM). In order to approach uncertainty evaluation of thermographic measurements, a new thermographic calibration and measurement procedure was developed at the National Institute of Standards and Technology (NIST). This method takes from procedures used with single-point radiation pyrometers, which have a more developed background in uncertainty evaluation stemming from their use as calibration transfer instruments. This report details a methodology for calibrating a thermal camera and obtaining temperature measurements, including measurement of emissivity and point spread function. This procedure is performed as a ‘post-processing’ technique which does not require the camera operating software to convert camera signal to temperature values. In-camera or manufacturer provided calibrations and temperature conversion algorithms may provide sufficiently low measurement uncertainty, however these results are often ‘hidden’ within the camera operating software and are not readily available for thorough uncertainty analysis, or, these algorithms are known but their form inhibits analytical means for uncertainty analyses. The methodology described here is designed as a framework for future development of analytical derivations of measurement uncertainty. The detailed process also includes methods for measuring and reducing identified sources of uncertainty (e.g., point spread function) that are otherwise neglected in most thermographic measurement procedures. Disclaimer: This document is an official contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States. The National Institute of Standards and Technology does not recommend or endorse commercial equipment or materials, nor does it imply that the equipment or materials shown are necessarily the best available for the purpose. ii TABLE OF CONTENTS Abstract i Table of