Abstract

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Infrared thermometers for non-contact temperature measurement are highly developed sensors which have wide-spread application in industrial processing and research. This paper describes, in non-mathematical terms, the theory upon which the measurement technology is based, and how this is used to deal with the variety of application parameters which confront the intending user.

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Introduction

An infrared thermometer measures temperature by detecting the infrared energy emitted by all materials which are at temperatures above absolute zero, (0癒elvin). The most basic design consists of a lens to focus the infrared (IR) energy on to a detector, which converts the energy to an electrical signal that can be displayed in units of temperature after being compensated for ambient temperature variation. This configuration facilitates temperature measurement from a distance without contact with the object to be measured. As such, the infrared thermometer is useful for measuring temperature under circumstances where thermocouples or other probe type sensors cannot be used or do not produce accurate data for a variety of reasons. Some typical circumstances are where the object to be measured is moving; where the object is surrounded by an EM field, as in induction heating; where the object is contained in a vacuum or other controlled atmosphere; or in applications where a fast response is required.

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Designs for an infrared thermometer (IRT), have existed since at least the late nineteenth century, and various concepts by F were featured by Charles A. Darling (1) in his book "Pyrometry," published in 1911. However it was not until the 1930's that the technology was available to turn these concepts into practical measuring instruments. Since that time there has been considerable evolution in the design and a large amount of measurement and application expertise has accrued. At the present time, the technique is well accepted and is widely used in industry and in research.