In the paper is proposed an original calibration method for microcalorimeter measurements on thermistor power sensors and certain preliminary experiments are illustrated, which are necessary for the effective application of the method. This new method avoids some critical steps in the usual microcalorimeter calibration, saves the time and does not require vectorial measurements for the feeding path sections.

Any practical oscillator has fluctuations in its amplitude and frequency. These fluctuations represent random amplitude modulation and phase jitter in the time domain. In the frequency domain there is a broadening of the signal frequency spectrum around a nominal frequency. The basic noise is a quantification of the quality of each oscillator and generator, and a measure of the quality of the equipment and of the system in which they are used. These noises determine the external interference immunity of all equipment and the interferences generated in the most frequent applications, in radio communication systems by themselves will work outwards.

This paper presents the derivation and effects of a genuine algorithm for identification of circular parametric operators describing performance of periodically time-varying systems, of one input – one output type. The periodic steady state is taken into the consideration, while the period of the change of the system parameters overlaps the period of the changes of input and output signals. Within the domain of discrete time, such operators take the form of a real element matrix. A circular parametric operator may be transformed into the frequency domain. In this version, the quantitative assessment of mixing and generating of harmonics of input and output signals is possible. The original identification algorithm is used for determination of time-varying two-terminal impedance. Some results of computer simulations are presented.

In two parts of this paper is presented the synthesis of some author’s works on unified backgrounds of immitance multivariable (nD) measurements of few jointed variables and on the unconventional signal conditioning in four terminal (4T) bridge circuits used for that. In Part 1 four different circuits for 2D measurements are proposed. Short description of equations and main parameters of the 4R bridge as twoport type X of variable parameters and then as circuit 4T unconventionally supplied by two current sources, named double current bridge (2J) are given and shortly discussed. In Part 2 application of both types of 4R bridges for 2D measurements is presented and discussed in details.

Accurate dc current transformers (DCCTs) are required for high current precision power supplies- Three basic categories of devices are available: devices which uses Ohms law (V=RI) called current shunts, devices which use Amperes law ( ∫ Hdl =ΣI ), called magnetic current sensors, and devices which uses both, called direct current transformers, DCCT’s The novel DCCT (NDCCT) uses Amperes law, and a reed relay (RR) as magnetic current sensor to detect when the primary and secondary ampere-turns would exactly be equal in magnitude and opposite. RR detects the zero flux condition occurring at the outlined balance condition. NDCCT is a clamp-on current probe. Two versions of NDCCT are illustrated, the one as dc current comparator and the other DCCT. By test results on an experimental NDCCT an uncertainty of 1.410-7 on the ratio error at 1 kA of the primary current is achieved.