9762 papers found
The accuracy of instruments for measurement a magnetic induction depends on a multiplication error of a sensor. It is considered the new algorithms of this error reducing by mean of a pilot signal with uninterrupted and periodic comparison and also with the negative feedback with respect to envelope of signals.
The problem of the metrological qualification of data acquisition systems and of waveform recorder is a fundamental issue for both users and manufacturers of digital instruments. The need for an improved industrial standard leading to unification and standardization in this field is a very pressing requirement. Users have to receive technical specifications written in standard format and manufacturers to obtain them following standard test procedure. The Main goal of this paper is to underline the need of unifying the modeling, identification and optimization of ADC-based systems, by...
The idea of acquiring not the proper samples at the input of an ADC but the difference ("Delta" and its sign "Sigma") between the new sample and the previous one (the derivative of the signal, in finite-difference sense) led to an important decrease of samples’ dynamic, provided the over-sampling frequency goes towards the slew-rate of the conversion circuits divided by the last significant bit. Considering the previous sample as the simplest (1-st order) estimate of the new sample, the authors modeled a more efficient way (in terms of speed and memory requirements): the acquisition of the...
In this paper, we propose a visual feedback system for a neuroanatomy. The stereoscopic microscope image of the dentate gyrus of adult rat brain in the neuroanatomy is converted into a black and white image. By the region segmentation, the region of the dentate gyrus is extracted. A binary image is obtained from a microscopic photo of cresyl violet-stained coronal section of the rat brain as a template. By the template matching, the apex of the dentate gyrus is automatically detected. The visual feedback system consists of a stereoscopic microscope, a micromanipulator, two CCD cameras and a...
A calibration method for a system designed to measure complex voltage ratios is presented. The method is based on the application of an AC transformer bridge. The system comprises a multichannel data acquisition board with simultaneous sampling, input adaptation circuits and dedicated software. An analysis of the accuracy of the proposed calibration method is made. Experimental tests of the calibration system were performed for signals differing in phase by π/2 and π at frequencies from 50 Hz to 1 kHz.
A method for the reduction of quantization errors in compressed multichannel RGB images is presented. The proposed method adopts fuzzy relations among neighboring pixels in order to reconstruct the data corrupted during the coding process. Results of computer simulations show that the method is simple and effective. Unlike other techniques in the literature, no complicated tuning of the parameters is necessary. Blocking and ringing artifacts are effectively reduced and the quality of the image is satisfactorily preserved.
Switched Current (SI) is a very interesting analog technique to perform interface circuits in mixed analog/digital systems because it is compatible with a low cost digital CMOS process (single poly technologies). The attempt of this work is to shed some light on the SI delta-sigma converter design method making use of an analog Hardware Description Language. To demonstrate the performances of the HDL-A model to optimize delta-sigma converters, a first order SI delta-sigma modulator has been designed, simulated and implemented using a 0.7 mm CMOS digital process. Also we have compared the...
An automated system for dynamic testing of ISA, PCI and VXI modules in frequency range up to 1 MHz developed at Department of Measurement of FEE CTU Prague is presented. The application of the Hewlett-Packard E1430A high precision VXIbus digitizer for evaluation of testing signals is described.
In this paper a novel approach for the direct computation of the probability density function (pdf) at the output of generic memory-less nonlinear processing blocks is derived. This method has been applied to the modeling of the THA-ADC chain. By using this approach, we are able to determine the exact behavior of the Signal to Noise Quantization Ratio (SQNR) of the THA-ADC chain for cases where the well-known Pseudo Quantization Noise (PQN) model do not give accurate results. The model can be easily improved to take into account for the ADC non idealities such as saturation and nonlinearity...
System for measurement of dynamic hysteresis loops is based on a pair of measuring ADC boards. Influence of different phase shift in both channels causes false phase information in the digitised signals. The character of the phase shift was identified as transport delay and its frequency dependence was measured. Software correction was implemented and tested. Study of the effective number of bits of resolution is also presented.