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Generalisation of traceability in LVD to other directives case study Testing of ear thermometers

Ear thermometers are clinical thermometers, which have to be tested for their accuracy. Their overall requirements and performance fall under the Council Directive 93/42/EEC. General test requirements are written in different standards (designation E-1965-98 ASTM 1998) or draft standards (prEN 12470-5:2000, Draft of JIS, Infrared ear thermometer, JMIF 2001). If the test of an ear thermometer shall determine its required accuracy all uncertainty components of auxiliary equipment shall be negligible compared to the uncertainty of an ear thermometer itself. One of the critical uncertainties represents the uncertainty of temperature due to the characteristics of a blackbody radiator (temperature stability and homogeneity, emissivity). The requirements for a blackbody radiator are very strict but it is very hard to determine their absolute values especially the emissivity. We will perform the analysis and comparison of different shapes of blackbody cavities according to the mentioned standards (and drafts) plus we will introduce a new shape. All the cavities will be analysed in terms of emissivity calculation and mounted in the same water bath. Blackbody radiators with different cavities will be evaluated also in terms of temperature stability and homogeneity. The comparison analysis will show how influential are other parameters besides an ear thermometer itself in testing of clinical ear thermometers to their overall accuracy.

First outcome in the scope of this task was the doctorate thesis of Igor Puanik. An important part of the thesis consists of description of experiments related to ear thermometers and technical requirements based on the requirements of the Medical Device Directive and related standards.

The second outcome were three articles related to the topic of the task, which were published in the SCI journals of the Institute of Physics:
Puanik I., E. van der Ham, Drnovaek J., IR ear thermometers - what do they measure and how they comply with the EU technical regulation, IOP Physiol. Meas. 25 (2004) 699-708
Puanik I., Simpson R., Drnovaek J., Bilateral comparison of blackbody cavities for calibration of infra-red ear thermometers between NPL and FE/LMK, IOP Physiol. Meas. 25 (2004) pp. 1239-1247
PU`NIK, Igor, DRNOV`EK, Janko. Infrared ear thermometers - parameters influencing their reading and accuracy. Physiol. meas. (Print). [Print ed.], 2005, vol. 26, pp. 1075-1084.

The third outcome of the task was a patent granted by the Slovene patent office. PU`NIK, Igor, BOJKOVSKI, Jovan, DRNOV`EK, Janko. Kopel za socasno umerjanje medicinskih brezkontaktnih in kontaktnih termometrov: patent atevilka 21628: patent je podeljen z odlocbo at. 600-198/04-JM-5 z dne 3. 5. 2005. Ljubljana: Urad RS za intelektualno lastnino, 2005. Copy of the patent document is enclosed to this report. The holders of patent filed also an inquiry for the patent at European patent office in Munich. At the end of the project the application was still under consideration. Copy of the application is enclosed to this report.

As a spin-off result of this task and based on published articles Dr. Igor Puanik was invited by the convenor of the OIML - Organisation Internationale de Metrologie Legale dr. Jurgen Hartmann from Physikalisch-Technische Bundesanstalt Berlin-Braunschweig, Germany to participate in the standardisation work for development of the new joint OIML and ISO standard on clinical thermometers. At the meeting of the working group ISO/TC 121/SC 3/JWG 8 in December 2005 at DIN, Berlin, Germany, Dr. Puanik was nominated as a member of the working group for preparation of testing methods for clinical thermometers. By the end of the project, 3 meetings were held (Berlin, Germany; Washington, USA; Limassol, Cypruss). At the meetings the international standard was developed to the stage of a committee draft and more than 500 comments from interested parties received through their national standardization bodies were discussed. The work will continue with the next meeting in April at the DIN, Frankfurt, Germany and later according to the needs. It is expected that the standard for clinical thermometers could be adopted by the end of 2008.

Another spin-off of this task was the inter-laboratory comparison of blackbodies for calibration of ear thermometers between the national measurement institutes in Europe. The EUROMET comparison was initiated during the EUROMET TC THERM meeting on 5./6. April 2005 in Vienna. MIRS/FE-LMK was chosen to be the pilot laboratory. The procedures and instructions, which are given in the protocol, should be followed by all participants. Each laboratory should follow its common practice in calibration of infrared ear thermometers (IRETs), when calibrating IRETs against their own blackbody. The objective of the inter-comparison is to determine agreement of blackbodies and procedures in calibration of IRETs among European national laboratories.

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University of Ljubljana
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