In this paper we present an 8 bits CMOS-only Digital to Analogue Converter (DAC), which has been used to introduce complex signals inside of a system based on an array of discrete elements. The design and the test are designed taking into account the nature of its application.

To estimate the measurement uncertainty using a modular DAQ system, factors influencing the quality of A/D modules have to be determined. While integral and differential non-linearity describes the static quality of an ADC, the effective number of bits or SINAD are typical integral parameters characterising the dynamic quality of an A/D module. The paper analyses how individual disturbing factors and imperfections of the A/D module influence the quality of digitalisation, and how they could be specified for a future standardisation. It is shown that (in the case of a time-variable input signal) the factors mentioned above induce disturbing undesirable components in the digital output and so they influence the value of SINAD of the investigated A/D module.

The paper describes the architecture of a distributed web-based measurement system able to disseminate measurement data over the Internet. After drawing the general architecture here proposed, the paper goes on describing, in somewhat detail, (i) the design choices adopted, (ii) the solutions implemented in order to correctly manage the measurement equipment also in presence of multiple connections, (iii) the assessment for maintaining a high degree of both generality and portability. Finally, a first application concerning a measurement station for the dissemination of environmental quantities over Internet is reported, in order to highlight the capabilities of the proposed architecture.

A measurement station able to carry out reliable non-destructive testing on conductive materials was set up and tested. It is characterised by a high flexibility thanking to suitable user interfaces that allows an easy definition of the scanning and measurement parameters. An adaptive scanning strategy allows a reduction of the investigation time by optimising the scanning step in function of the measured data. Experimental results on a number of specimens with known cracks prove the effectiveness of the realised station.

Monitoring the intensity of the reflected spot in a RHEED image is the most important method used to control the growth of semiconductor crystals in facilities like for example MBE. In some application the availability of the spot intensity signal as an analog voltage is also useful to realize a feedback between the growth dynamics and the external parameters of the plant, such as the cells temperatures and the synchronization of the shutters. Although said analog signal could be obtained by using a photo-detector near the RHEED screen or grabbing and digitizing the RHEED image, these methods are troublesome or expensive respectively. In this paper a simple and cheap solution, based on a synchronized sample and hold operation on the composite video signal, is proposed.