Methods enabling a determination of errors eI and dI for a high transformation ratio difference between a standard and tested instrument current transformers (ICT) are described in this article. A widespread method uses an automatic transformer test set for the measurement of a difference between a standard and tested ICT. A method transforming secondary currents to voltages and an indirect method using error measurement from magnetizing current are also described.

A measurement process represents a controlled learning process in which various aspects on uncertainty analysis are investigated.
A measurement process is performed if information supplied by it is likely to be considerably more accurate, stable and reliable than the pool of information already available.
The substantial amount of information, got with respect to the conditions prior to the result after the measurement process is performed, can be connected to the "Kullback's principle of minimum cross-entropy".
This, as it is known, is a correct method of inductive inference when no sufficient knowledge about the statistical distributions of the involved random variables is available before the measurement process is carried out except for the permitted ranges, the essential model relationships and some constraints, gained in past experience, valuable usually in terms of expectations of given functions or bounds on them.
In this paper the authors pointed out the connection between the evaluation of the uncertainty in a repeated measurements process and the "Kullback's principle of minimum cross-entropy".

In this work are analysed performance of quality assurance in the Estonian measuring instruments verification laboratories. During last 10 years had Estonia changed completely and this involves also activity on the metrology area. Basic change was case, that on the previous period the verification was mandatory for almost all measuring instruments, now shall it be replaced greatly by voluntary calibration. But verification stays highly required service. Verification area involves mainly measuring instruments which are used in affairs. New is also fact that now-a-days verification laboratories are more commonly private companies and public authorities carry out only market surveillance. To get stability of work laboratory shall implement quality system.
Above was ground for this work and analysed are the quality and competence assurance in the verification laboratories. Based on the accreditation data are analysed the critical points of quality assurance. In a summary is given conclusion of actions which can be used for restructuration of metrological infrastructure especially in measuring instruments verification area.

In our recent papers we have dealt with the assessment of the uncertainties associated with the virtual instrument measurements, proposing two completely different methods. The first one is based on an original application of the "uncertainty propagation law" of the ISO "Guide to the expression of uncertainty in measurement". The second one is a numerical approach, based on the Monte Carlo simulation. In this paper we show how the proposed approaches can be implemented in the virtual instruments in order to make the instrument itself able to auto-estimate the measurement uncertainties.

This paper contains the processing formula of an inductive transducer in an immersion version for contactless measurements of conductivity of conductive media. In this version, a winding has been wound round an insulating stick in the form of a short coil. Such a construction enables us to easily place the transducer in the investigated medium. Dependencies determining the influence of the electric and magnetic properties of the walls of the vessel, which contains the investigated medium upon the transfer function of the transducer have also been formulated. These dependencies can also be used to designing the transducer in a shield with aforementioned properties. Moreover, experiments have been carried out which consisted in the measurement of the conductivity of the H₂SO₄ electrolyte solutions of known concentrations in a constant temperature by means of the transducer designed and using the theoretical dependencies derived. The results obtained demonstrate that the measurements – by means of the proposed methodology – can be carried out with a sufficient accuracy.