CONTAMINATION OF PLATINUM RESISTANCE THERMOMETERS BY SILVER

Mass spectrometric analysis shows that platinum resistance thermometer s become contaminated by exposure to Ag and Cu at high temperatures. T o study the rate at which such contamination occurs. bundles of Pt wir es in quartz tubes were soaked in a silver fixed-point furnace. The re sults suggest that the sensing element of a platinum resistance thermo meter (PRT) inserted into an Ag-contaminated thermometer well will beg in to become contaminated after approximately 400 hours of accumulated use at the sliver point. The experimental results suggest that the co ntamination may be avoided by interposing an additional, disposable qu artz tube between the contaminated thermometer well and the PRT.