Noise measured across silicon single-crystal solar cells may serve as a non-destructive reliability indicator of the devices. The noise sources in monocrystalline solar cells has been described. The noise measuring system and the results of measurement of circular form cells (a diameter of 100 mm and a thickness of 360 µm) have been presented. The DLTS measurements performed on investigated solar cells approved the noise measurement results.
The properties of some algorithms based on digital signal processing for the impedance components evaluation in circuits with sampling sensor have been analysed. It is supposed that the voltage and current are sampled synchronously to the fundamental frequency of the generated sinusoidal signal. Two groups of fitting sine wave algorithms, which are based on the least mean square (LMS) technique, have been described. The first one reconstructs indirect measurement method. The second group of algorithms estimates the unknown impedance components by direct method. In all these algorithms to...
In this paper a Nuclear Magnetic Resonance magnetometer (NMR) in a form of a LabVIEW Virtual instrument (VI) is proposed. The heart of the magnetometer remains the marginal oscillator with a proton sample. The magnetic resonance signal and all other auxiliary signals are generated and controlled by a set-up composed of a digital counter (for resonance frequency measuring), a VXI system (for the modulation signal generation and for the sampling of the oscillator output), a programmable DC voltage source (for oscillator frequency control) and a personal computer controlling the measurement....
A transportable high stable reference AD device was designed and realised for a comparison of systems for testing a dynamic quality of ADCs or AD modules two years ago. In spite of the fact that several comparative measurements were successfully executed, some limitations and imperfections were found out. Therefore a new innovated version of the device was designed and developed based on existing experiences. The new solution is described in this paper.
The characteristics of analog-to-digital converters (A/D converters) are established and assessed based on the results of the conversion of a sinusoidal signal. This method of measurement has been selected because it is relatively easy to generate sinusoidal signals with the required good parameters. Among the criteria of the measurement of an actual a-d conversion is the probability density function (PDF) of the quantization error. Unfortunately, the distribution of the PDF of the error of the quantization of a sinusoidal input signal is not rectangular (because sinusoidal signals do not...
The software validation of measuring instruments is a complex procedure, which can be divided into the validation of separate software functions. The paper deals with the software validation of functions for serial line communication. It describes methods for preparation and validation. Methods are based on demands and facts, which are important for measuring instruments under legal control. They were developed during type approval process of an automated liquid level measuring instrument, but they can be easily adopted and used with other measuring instruments or communication interfaces....
IEN system for unlike impedance comparison (resistance vs. inductance, or resistance vs. capacitance) is based on an implementation of the three-voltmeter method, which configures both standards in comparison as four terminal-pair, by using automatic electronic compensations to achieve the purpose. Basic relative accuracy of the instrument is between a few parts in 10 -6 for comparison of impedances in the range 10 Ω to 10 kΩ, and at frequencies in the range 100 Hz - 10 kHz. The same system, without any changes in the instrumentation employed or its wiring, can be effectively used also as a...
The paper presents problems of compressing measurement signals recorded under long-lasting monitoring conditions. The criteria for compression method selection in view of its efficiency (compression ratio) and quality of conversion (coding-decoding procedure), with regard to dynamic properties of the measurement signals are discussed. Attention is given to the interdependence of the achieved compression ratio and the distortion level. A method is proposed for generating synthetic test signals to investigate the efficiency of lossy compression methods, which enables unification of the...
It is noticed in the paper that scaling of digital measurement signals and their registration in format which is comfortable to investigations during computer processing increase their volume. Possibility of realization a reverse scaling operation as an initial processing method preceding compression is mentioned. The authors proposed to complete initial processing by generally well-known operation - calculation of differences between succeeding samples and they tested the additional compression ratio, resulting from the proposed transformations, using experiments.
The monitoring of a few critical parameters during epitaxal growth is necessary in order to obtain high quality III-V semiconductor heterostructures. We have developed an electronic circuit that is able to perform realtime analysis of the spatial distribution and intensity of RHEED (reflected high energy electron diffraction) patterns by means of a CCD camera. Besides being used for obtaining information from RHEED patterns, the new system can also be employed for in situ and real time stress measurements during molecular beam epitaxy of lattice mismatched heterostructures.