Kálmán Máthé

Improved version of the printed circuit board (PCB) modular multi-channel microdrive for extracellular electrophysiological recordings

The modular multi-channel PCB microdrive was described some years ago, since then several improvements were introduced while using these drives. Utilizing several years of experience with the original PCB microdrive we redesigned it to improve its stability and usability. The application of the printed circuit board technology and the extensive use of flexible fused silica capillaries for fabrication of the microdrive are described in detail. The improved design led to a low cost and light-weight multi-channel microdrive with outstanding modularity for extracellular field, single unit or multiunit tetrode recording up to 64/128 channels.

The application of cross-point switch arrays as input selector switch devices for multi-channel electrophysiological experiments

Integrated circuits (ICs) containing cross-point switch arrays were applied to create analog input selector switch devices for multi-channel electrophysiological experiments. The described analog input selector switch devices make it possible to connect to the main amplifiers inputs those microelectrode and preamplifier output wires that yield unit discharges of acceptable shape and amplitude, or yield other kind of acceptable electrophysiological signals (EEG, EP). This kind of selector allows to use higher number of preamplifier channels and to ignore the input channels without adequate signals or the channels with noisy inputs. No manual switching is required, as the work is done by computer controlled switches. The switch positions can be saved and reloaded at the next experimental session through an I/O port (e.g. the parallel port) of the computer.

Implementation of a galvanically isolated low-noise power supply board for multi-channel headstage preamplifiers

Custom made multi-channel headstage preamplifiers are traditionally powered by battery. By the use of an isolated unregulated DC/DC converter integrated circuit (DCP010512B from Texas Instruments Inc., TX, USA), here we describe the implementation of a galvanically isolated low-noise power supply board for multi-channel headstage preamplifiers. The implemented galvanically isolated power supply board provides the same quality noise free recording as the battery power supply. The non-isolated part of the power supply board is powered by standard 230 V AC/6 V DC wall mount adapter or USB cable. The described galvanically isolated power supply board can replace the batteries in preamplifier power supplies without any deterioration of the quality of recordings.

DSP platform for 64-channel brain cell signal preprocessing

The problem of correct radio telemetry can only be solved if the signal is preprocessed. This work presents the pre-distortion and reconstruction process of a real time signal, and its effects.

Implementation of a miniature sized, battery powered electrophysiological signal-generator for testing multi-channel recording equipments.

Testing electrophysiological recording equipments is an important task in multi-channel extracellular in vivo electrophysiology. In this paper, a miniature, battery powered multi-channel electrophysiological signal-generator (ESG) is described that was designed for this purpose. The device is based on a Xilinx CPLD (Complex Programmable Logic Device) and it is powered by a 3V lithium coin battery. It is a useful tool for calibration and testing the performance, quality and parameters of the recording equipments used for acquiring EEG, field potentials, ECG, EMG, and multiple unit activity. The device is ideally suited to identify instances when errors interfere with the proper recording, and repair of wiring or service of the equipment is needed. Two versions of the device are described; one is for 16 (ESG16), and another is for 32 channels (ESG32). Both versions provide amplitude and time calibration, as well as cross-talk and CMRR (common mode rejection ratio) testing for the recording equipment.

Realization of protocol conversion for high speed data acquisition system

In computer networks data flows can often reach transfer rates of several Gigabits per second. On the other hand most embedded systems have additional criteria — power consumption, size, low cost, generated heat — which usually means that even a flow rate of several Megabits per second is difficult to reach. This paper reports on the development of an automated embedded system for data transfers of up to 47Mib/s using two customized embedded 68k/Coldfire RISC microprocessors.

Multi-Frequency Electrical Impedance Measurement on a Wooden Disc Sample

Abstract Non-invasive measurement techniques are widely used for the investigation of living tree and wood material. Principles and methods from other fields of science form the basis of these techniques. Electrical impedance measurement, which is adopted mainly from applied geophysics, plays an important role in the investigation of living trees and wood material. Unlike other measurement techniques that provide mainly physical information, electrical impedance measurement is able to gather either physical or chemical information. There are several published accounts of the use of Electrical Impedance Tomography mainly for examining internal decay, estimation of sapwood, and heartwood width. The advantages of the method are its low costs and rapid execution; however, low spatial resolution is still one of the most glaring limits of the method. Use of a new, self-developed, high resolution measurement system provides new opportunities to gain better insights into the characterisation of wood material. As well as high accuracy and resolution, the measurement system is able to operate in a wide frequency range. This expands the examined parameters making it possible to extend the gained information and develop new methods for the investigation of living trees and wood material. The aim of our publication is to introduce some experimental results in the investigation of spatial resolution our system measured on a wooden disc. Kivonat Fakorongok multi-frekvenciás elektromos impedancia mérése. Az előfak es faanyagok vizsgalatahoz kulonboző merestechnikai eljarasokat alkalmaznak. Ezek alapjat elsősorban mas tudomanyteruletekről hozott elvek es modszerek kepezik. Az elektromos ellenallas (impedancia) meres, melyet a geofizikai gyakorlatbol adoptaltak, ezek kozott nem kevesbe fontos szerepet tolt be, ugyanis mig a meresi modszerek tobbsege szerkezeti, fizikai informaciot szolgaltat, addig az elektromos modszerek a fizikai mellett kemiai informacioszerzesre is alkalmasak. Az Elektromos Impedancia Tomografiat tobb izben publikaltak előfak eseteben uregek, illetve szijacs es geszt vastagsag becslesre. Bar a meresi eljaras előnyei koze sorolhato a relativ alacsony koltsegigeny es gyorsasag, osszevetve azonban mas kepalkoto eljarasokkal, a kisebb terbeli felbontas szab hatart az egyes alkalmazasok elterjedesenek. Egy uj, sajat fejlesztesű nagy felbontokepessegű merőeszkoz alkalmazasa uj lehetősegeket nyujthat a felbontas javitasaban es a faanyag jellemzeseben. A merőeszkozre jellemző, hogy a nagy pontossagu es felbontokepessegű mereseket igen szeles frekvencia-tartomanyban kepes kivitelezni. Ez egy uj dimenziot nyit meg az előfa es faanyag vizsgalat modszertanaban, mely egy uj meresi eljaras fejleszteset alapozhatja meg. Jelenlegi publikacionk celja merőeszkozunk terbeli felbontasanak kiserleti ellenőrzese faanyagon.

Application of the FPGA technology in the analysis of the biomedical signals

Over the years the acquisition and analysis of bioelectrical signals in humans has become more and more important for advancing in the medical treatment. In every living organism there are millions of bio-electrical signals and extracting just one of them is a very challenging engineering task. This paper presents a device specially developed for biomedical researches of the signals in extreme noise environments which uses lock-in amplifiers and tuned filters for the spectral and impedance measurements. The practical realization of this system demanded high speed multichannel parallel algorithms which could only be implemented in the FPGA technology. The device is intended for use in multiple medical researches such as determining the influence of the medical probes on the living tissue, measuring deviations in the impedance between healthy and diseased tissue, registering the presence of viruses in the blood samples and analysis of the brain bio-electrical signals.

Thermopile battery, thermoelectric generator as the only possible alternative for future

Sun supplies the purest energy available on the Earth. Hungary and Serbia seems to be even further from this energy source free from CO2 emission, since in spite of the fact that, these states has excellent geographical features neither our present governments non supports this issue to a sufficient extent. A correct purchase price of solar energy should be determined in harmony with the European directives, as nearly all our neighbouring countries have higher achievements in utilising renewable energy sources. Today thermopiles can be found in various applications for temperature or radiation measurements and for electric energy production. It is in the initial stage, especially space technology applications. There exist, for example, surface temperature sensors, gas sensors based on the Lambert-Beer law of absorption, and vacuum sensors. Based on the thermoelectric effect, the thermopile can be used as a heat sensor to measure thermal radiation. A thermopile is made of thermocouple junction pairs connected electrically in series. The absorption of thermal radiation by one of the thermocouple junctions, called the active junction, increases its temperature.