NIST-NPL Bilateral Comparison of Guarded-Hot-Plate Laboratories from 20 °C to 160 °C
Robert R. Zarr, Jiyu Wu, Hung-Kung Liu
A bilateral study to compare guarded-hot-plate measurements at extended temperatures be-tween laboratories at the National Institute of Standards and Technology (NIST) and the National Physical Laboratory (NPL) is presented. Measurements were conducted in accordance with standardized test methods (ISO 8302 or ASTM C 177) over a temperature range from 20 °C to 160 °C (293 K to 433 K). Following a blind round robin format, specimens of non-woven fibrous glass mat, approximately 22 mm thick and having a nominal bulk density of 200 kg∙m 3, were prepared and studied. Results of the study show that the thermal conductivity measurements agree over the temperature range of interest to within ±1.0 %, or less. Consensus and individual laboratory fits to the data as a function of mean temperature are presented graphically. Sources of measurement variability are addressed.