IR ear thermometers: what do they measure and how do they comply with the EU technical regulation?

Medical diagnostics and clinical practice rely extensively on test and measurement instrumentation. It is therefore of paramount importance that test and measurement instrumentation provides reliable data of sufficient stability, within appropriate limits of accuracy. At the same time the intended purpose of a particular measuring instrument has to be taken into account. The essential problem of every measuring instrument is that it measures and indicates basically what appears at the input of the measuring instrument, which might be significantly different from the real condition of a measurand. Namely, it is assumed that a measurand is stable, repeatable, and relatively unsusceptible to environmental influences. All these requirements are difficult to assure in a biological system and especially difficult in medical practice. Technology could easily provide high-resolution measurements, but due to natural instability of a measurand and various influential parameters the measurement uncertainty is inevitable. Sometimes even gross measurement errors are introduced. To achieve the expected accuracy for intended purpose is therefore much more demanding than merely relying on manufacturers' specifications. This paper describes and analyses the mentioned dilemmas in the case of widely used infrared ear thermometers, with their benefits and limitations, as well as with regard to the European technical regulation in the field of medical devices.