The paper presents results of an international comparison of two quantum AC Josephson Voltage Standards based on pulse- driven Josephson arrays. The two systems differ in several hardware and software characteristics as well as in the level of automation, features which can influence the accuracy of transferring the quantum -standard voltage value to a calibrated instrument. The comparison was conducted at 100mV, 20mV and 12mV, at frequencies between 2.5kHz and 100kHz. An electronically-aided thermal transfer standard was used as a travelling standard. At the most accurate voltage and frequency point, 100mV at 2.5kHz, both laboratories agreed to better than 1 part in 106.

This work presents the prototype of a standard for HVDC, designed to be used in the range of 1 kV to 50 kV and calibrated in low voltages. In HV, it will be the link in the chain of traceability between the INMETRO standard and the dividers used by industrial laboratories.

Adaptive Optics has become an important technology to reduce the effect of wavefront distortions. It is used, for instance, to compensate the effects of atmospheric distortion in astronomical telescopes and to reduce the impact on the quality of the retinal image caused by optical aberrations inserted by the cornea and eye optical path. A wavefront sensor is an important part of an adaptive optical system and in the Hartmann-Shack method three parameters must be estimated prior to the wavefront estimationstep: the distance between the microlens array and the image sensor chip; and the pixel pitches in the X and Y directions in the Hartmogram image. This paper presents one method to estimate the actual distance between a microlens array and an image sensor; and another method to calculate pixel pitches, both based on image processing techniques and geometric analysis.

A coaxial microcalorimeter based on thermoelectric detection is the system used to realize the broadband primary power standard at high frequency by Istituto Nazionale di Ricerca Metrologica, Italy. The paper describes and compares two analysis methods that can be applied to the measurement data for evaluating the overall system uncertainty. Methods are completely general and we applied them to our measurement system that can operate with 7 mm, 3.5 mm and 2.92 mm coaxial insets, covering, therefore, the frequency range of 10 MHz -40 GHz.

Symmetricom has developed a Time Scale System that incorporates advanced measurement, sign al processing, and algorithmic techniques to provide an automated solution suitable for a national time scale. The total system includes two redundant time scale sub-systems with automatic output switching in case of a failure. Each time scale creates a real-time UTC(lab) output including such signals as 1 PPS, IRIG time codes, serial time code, 5 and 10 MHz, NTP, and PTP. The base system supports up to 6 local clocks, which may be either cesium standards or hydrogen masers and additional remote clocks. Input switching of the clocks is used so that failure of an individual clock does not cause a failure of the UTC (lab) output. The time scales use the KAS-2 algorithm to create a free time scale called TA (lab) [1], [2], [3]. A coordinated paper time scale is formed by steering relative to the free time scale using measurements from either the GNSS receiver or Circular-T. The UTC (lab) output is generated by steering a synthesizer to the coordinated time scale. The paper presents the overall system design as well as details of the time-scale algorithm, robustness algorithms, and steering algorithms. Performance data are presented.