Importance,Organization and Evaluation of Interlaboratory Tests

The importance of ＂precise＂ test values and their verification is growing in every industry throughout the world, lnterlaboratory studies constitute a basis for this. The high expenses and mathematical work required to carry out proper interlaboratory studies are frequently considered reasons not to conduct such studies. This makes it all the more important to emphasize the various advantages of an accurate interlaboratory study. In addition to providing precision data for the test method, it is also possible to carry out laboratory evaluations, which is important for accredited test laboratories. Furthermore, existing test methods can be optimized, refer- ence material can be obtained, and test methods can be compared. Optimized test instructions can also be generated using the findings and precision data. These advantages will be described in detail by means of examples below.

Round Robin Study on the Thermal Conductivity/Diffusivity of a Gold Wire with a Diameter of 30μm Tested via Five Measurement Methods

Since first establishing thermal measurement techniques for micrometer-scale wires,various methods have been devised and improved upon.However,the uncertainty of different measurements on the same sample has not yet been discussed.In this work,a round robin test was performed to compare the thermal conductivity and thermal diffusivity measurement methods for a fine metal wire.The tested material was a pure gold wire,with a diameter of 30μm.The wire was cut into certain lengths and distributed to four institutions using five different measurement methods:the direct current(DC)self-heating method,the DC heating T-type method,the 3ωmethod for thermal conductivity,the scanning laser heating alternating current(AC)method,and the spot periodic heating radiation thermometry method for thermal diffusivity.After completing the measurements,the reported thermal conductivity and thermal diffusivity at room temperature,i.e.,317 W·m^(-1)·K^(-1)and 128×10^(-6)m^(2)·s^(-1),respectively,were adopted as references for comparison with the measurement results.The advantages and disadvantages of each method are described in terms of the effect of electrical and thermal junctions fabricated on a wire,such as an electrode,a thermocouple,and a heat bath.The knowledge obtained from the tested methods will be useful for selecting and designing a measurement technique for various wire-like materials.

China’s participation in the international RRT for I_(c) measurement of superconducting cables organized by IEC/TC90

Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting cables.At the end of 2020,an international round robin test(RRT)was organized,in which five Chinese institutions participated,and four accomplished the test.The electric-field versus current(E-I)curves obtained by each institution are highly repeatable.Those obtained by different institutions are nearly identical after appropriate curve averaging,indicating high reproducibility,except the last participant's inner core curves.The discrepancy was later determined to be the result of sample cable damage.After excluding highly deviated data,it is determined that the maximum relative standard uncertainty in I_(c) is 0.7%,and the maximum relative standard uncertainty in n-value is 12.8%.The I_(c)values are comparable to Japan's domestic RRT results,but the n-values are significantly different.The test results support the DC four-terminal method as a recommended test method,with a target relative uncertainty of less than 2%for the Ic value.