A new concept of distributed IEEE-488 measuring systems using Java architecture is proposed. A connection of external modules (standard library for National Instruments IEEE-488.2 interface board) to source code in Java is described. Next, an example of the system, that uses a communication based on sockets for remote controlling of instruments, also via Internet, is presented.

The present work concerns magnetic circuits which are built of laminated soft magnetic materials, e.g. cores of transformers or of rotating machines. Such systems tend to show very complex local distributions of the magnetic field vector H, the induction vector B and the energy loss P. For simultaneous measurements of all these local quantities, we designed a hand-held sensor which can be arranged on the surface and - taking advantage from small sensor thickness - also between the core sheets. All data are displayed instantaneously on the computer screen. The measuring method is based on search coils for the planar components of H, and on the needle method for the components of B out of the electric field vector E. The losses P are derived from the Poynting vector S = E × H. The sensor proves to be an effective tool, e.g. for rapid investigations of T-joint regions in transformer cores which tend to show rotational magnetization. Apart from such practical applications, the present paper is focused also on fundamental problems of the novel sensor design.

The paper presents a new concept of virtual electronic scales (VES) conceived as a PC peripheral. The traditional approach, “specific scales for specific application”, has dominated the development and production of both mechanical and state-of-the-art electronic scales. The main aim of this paper is to promote a PCbased approach – electronic weight scales as a virtual instruments. The paper offers a detailed presentation of originally developed hardware and software structures of VES called Soft Scales, based on strain-gauge load cells, of 2 ... 200 kg measurement range, accuracy class III, up to 10,000 scale intervals. Finally, a list of specific applications and realisation of both trade scales and body mass index measurement sistem as a virtual instruments, together with a brief measurement-technical comparison between the classical and PC-based approach are presented.

The computer-controlled system for low-frequency noise measurements has been presented. All major functions for adequate polarisation of a device under test are programmable providing complete flexibility and automation for biasing. The inherent noise parameters of the main modules are enclosed. The system enables to measure input-output noise relations for BJTs, JFETs, MOSFETs, MESFETs, HEMTs, and, in general, also other two-ports.

A low-cost switch for ac-dc transfer is presented in this paper. The switch performs fast switching of the input of the thermal voltage converter (TVC) between AC and DC calibrator outputs. It can be controlled through the GPIB bus, manually and through the serial RS-232 interface. Both 4-wire and 2-wire connection between the TVC and the calibrators is possible. The switch provides very fast switching. The dead time of the switch is less than 5 ms. The switch is well protected against relay and power failures.