Low voltage AC-DC transfer standards at LNE
This paper describes the method used to establish the traceability of LNE AC-DC transfer standards in the mV-range to the 1 V multijunction converter, which serves as the primary AC-DC standard. Main uncertainty components are listed and final uncertainty given for the different voltage levels. An independent method was developed for the calibration of thermal converters at 0.3 V and 0.2 V. The agreement between this method and the step-down is within the standard uncertainty.
Automated comparator for accurate AC-DC difference measurements at the BNM-LCIE
This paper describes the new automated comparator system developed at the BNM-LCIE for the calibration of voltage thermal converters used as national AC-DC transfer standards. The system achieves Type A standard uncertainties of a few parts in 10/sup 7/ in the frequency range from 10 Hz to 1 MHz (100 kHz for voltages above 100 V). Type B standard uncertainties, depending on the type of converters to be compared and on the measurement voltage level, are between a few parts in 10/sup 7/ and a few parts in 10/sup 6/.
Low-temperature thermal expansion of PEEK, HTA and some of their composites reinforced with carbon fibres
Abstract The thermal expansion of poly(ether ether ketone), a modification of poly (ether sulphone) and carbon fibre reinforced composites of these polymers has been measured over the range −153 to 27°C with a push-rod diameter. Where other measurements are available for comparison, agreement is obtained within experimental scatter. Some multidirectional composites are tested and the measured values of thermal expansion are explained qualitatively. It is thought that the specimen size has had a significant effect on these results. The longitudinal and transverse coefficients of thermal expansion of Hercules AS4 fibre have been calculated.