The problems of metrological ensuring virtual measuring instruments (VMI) are discussed. The VMI classification is proposed. The principles of measuring instrument legalization are formulated as a base for the problem solving. As the basic problems, structural identification of VMI, and unauthorised access, and VMI calibration and standardization are pinpointed. It is shown that complete calibration is foreground for VMI similar as to usual measuring instruments, without necessity to certify, separately, measurement software.

The paper presents the derived dependence on the total noise factor of cascade-connected linear two-ports in the conditions of energy mismatching. The method of assessing the uncertainty in measuring this factor, which takes into account propagation of standard partial uncertainties of the measurement of the set of four noise parameters, disposable power gains and input and output impedance of particular two-ports, is determined. The uncertainty analysis takes into account the correlation among these parameters. A strict dependence between the mismatching stages of two-ports in the cascade and the uncertainty in measuring the total noise factor is shown. Sensitivity coefficients determining the participation of particular standard partial uncertainties are defined. The results of the analyses and simulations of particular uncertainties components, which were carried out for a typical communications receiver, are presented.

This protocol was developed to estimate the uncertainty of measurement of a chemical analysis by utilizing in-house validation studies and quality control data. The approach was to generate an estimate of the uncertainty across the analytical concentracion range. This was to be expressed as a mathematical equation or factor that could be inserted into a Laboratory Information Management System (LIMS) and thus produce an uncertainty estimate from an entered analytical result.
The aim is to identify as many sources of uncertainty as possible and account for them by appropriatte precision and trueness studies. Any additional sources of uncertainty are evaluated by other means such as calibration certificates, published dana, etc.. It is not necessary to evaluate every source of uncertainty if they are deemed insignificant, unless there are a large number of them. Uncertainty components that are less than one third of the largest component are not evaluated in detail. A preliminary estimate of the contribution of each component or combination of components to the uncertainty is made and those that are not significant eliminated . The uncertainty contributions is expressed as standard deviation, and combined according to the appropriate rules, to give a combined standard uncertainty. Coverage factor (2 for normal distribution) is applied to give an expanded uncertainty.

Electronic systems for automated monitoring of the presence of dangerous gases are available nowadays in different configurations and with quite different capabilities. This work is presenting the development of an electronic instrument for monitoring the level of two gases (namely CO and CH₄) aiming for possible use in coalmines. The instrument is using SnO₂ sensors and is based on a graphical estimation of the concentration of each of the two gases realised by a combination of the information from the calibration curves of the two sensors. In this way, instead of trying to suppress the well-known secondary sensitivity of these gas sensors, this method is estimating the two concentrations by a computerised approximation of the operating point on the calibration curves.

In this paper we present an overview of the electromagnetic field loop sensors measurement performances. The loop sensors are much utilised in electromagnetic field measurements (magnetic field measurement, simultaneous magnetic and electric field measurements). The knowledge of the influence of the dimensions sensor on measurement performances of the electromagnetic field is important both in sensor optimisation, and in the selection of the sensor for a certain application. The results of time domain measurements of the magnetic field near some appliances, made with an active magnetic field sensor, are presented.