Ing. Pavel Mlejnek, Ph.D.

The notion of theragnostic brings together such terms as telemedicine, bionanosensors, and personalized medicine. Synergy in the mainstream areas can bring new approaches and provide a fresh perspective on long-established areas. The present research aims to prepare technological equipment for evaluating and measuring functionalized nanomembranes with analyte. Due to the functionalization of nanomaterials, it is possible to capture selectively the analyte or the targeted group. It can be, for example, viruses, bacteria, dangerous chemicals, body fluids, or miRNA. Electronic and optical methods have been preselected for the biomarkers binding evaluation. Methods were selected as technically and scientifically proven. Optical methods have a leading place in “in vitro” diagnostics. In the long-term horizon, it can be used as a Nano Chip biosensor (Including Nano Receptor, Nano Biosensor, and microelectronics)

Článek popisuje změny, které nastaly v pololetí roku 2022 v souvislosti s účinností zákona č. 250/2021 Sb., o bezpečnosti práce v souvislosti s provozem vyhrazených technických zařízení a o změně souvisejících zákonů. Společně s tímto zákonem vešly v platnost i související nařízení vlády č. 190-194/2022 Sb. Z hlediska elektrických zařízení jsou pak relevantní NV č. 190/2022 Sb., o vyhrazených technických zařízeních a požadavcích na zajištění jejich bezpečnosti a NV č. 194/2022 Sb., o požadavcích na odbornou způsobilost k výkonu činnosti na elektrických zařízeních a na odbornou způsobilost v elektrotechnice. Jaké změny toto přineslo v oblasti činností na elektrickém zařízení a požadavcích na bezpečnost je cílem tohoto článku.

Nanocrystalline and amorphous stress-annealed and field annealed tapes are used for cores of DC-tolerant current transformers. We analyze the influence of external DC field of arbitrary direction on the performance of these transformers. For the realistic core shapes the demagnetization is high, which leads to effective external field suppression. However, DC tolerant transformers are tolerant to the DC component of the current and not to the external field -they can be saturated by 30 mT field from permanent magnet. This means that for the practical applications in domestic energy meters some external shielding is required.

Novel rectangular yokeless current transducer with the range 400 A using 16 microfluxgate sensors around the busbar conductor is presented in this paper. Compared to yokeless transducers utilizing the differential pair of magnetic sensors, our solution has much better suppression of the external currents (lower crosstalk). Compared to industrial transducers with yoke, the new transducer has 15-times lower noise, 7-times better temperature stability, and same crosstalk. The sensor design and design of the current monitoring system is presented together with the results of long-term field tests. Crosstalk error is examined in dependence on the number of operating sensors and the external current position.

We present a method of calibration and error correction of the AMR yokeless current transducer consisting of a circular array of eight anisotropic magnetoresistors (AMR) with one feedback compensation loop. The main sources of errors are the nonidentical parameters of AMR sensors and off-center position of the measured current. It is well known that AMR sensors from the same batch have 2% spread of the sensitivity; we found that the variation of the factor of the internal compensation coil is the same. We developed a novel calibration process using the readings of individual residual uncompensated voltages of the AMRs. The position of the current inside the measurement hole is estimated from the individual voltages considering the influence of external DC magnetic field such as the Earth’s field. During the calibration phase, the sensor outputs are measured for several positions of the current conductor inside the measuring hole. As a result of calibration the lookup table of error corrections is calculated and stored in the memory, and then these values are used for the correction during the measurement of the unknown current. This procedure reduces the off-center error from 0.4% to 0.06%.

Tento článek pojednává o principech detekce zvýšené vlhkosti, které využívá systém Moisture Guard. Článek se zabývá vyhodnocovacím algoritmem pro detekci havarijních stavů. Rozebírá rozpoznání běžných sezonních změn vlhkosti a problematických nárůstů ještě před dosažením kritických hodnot.

Tento článek shrnuje problémy spojené se zvýšenou vlhkostí v konstrukci dřevostaveb, které se podařilo odhalit tímto systémem v pilotních instalacích za přibližně 2 roky od jeho prvního nasazení.

We analyse the influence of real parameters of KMZ51 magnetic sensors on the accuracy and characteristic of AMR current measurement sensor. The device consists of a circular array of eight magnetic field sensors. The differences in sensitivity of individual AMRs, as well as bridge resistance, the resistance of compensation coil and compensation coil factor are discussed. Finally, we present the method how to compensate the mentioned errors by reading individual sensor outputs.

A complex system for continuous moisture monitoring in timber constructions will be introduced in this work. The main purpose of the developed system is to guard a wooden building or other timber construction against any failure resulting in increased moisture level in wooden structure. The whole system works on early warning principles in order to detect potential failures immediately and thus minimize costs related to reconstruction works. The detection process relies on combined humidity, moisture and temperature information provided by each distributed sensor installed in the building structure. The system is being tested both in laboratory conditions simulating several types of leakages and in real wooden buildings as pilot installations with promising results.

Dřevo se pro své vlastnosti stalo velmi populárním stavebním materiálem a tak podíl počtu dřevostaveb v celkovém počtu novostaveb rok od roku stále roste. Dřevo má však kromě svých pozitivních vlastností i svá rizika, mezi která patří i často opomíjená vlhkost. Zvýšená vlhkost velmi výrazně ovlivňuje životnost stavby a její zákeřnost spočívá v nemožnosti odhalit ji včas.

Tento článek volně navazuje na předchozí články o zvýšené vlhkosti v dřevostavbách a možném způsobu, jak ji monitorovat systémem Moisture Guard. Článek popisuje vyhodnocení monitoringu vlhkosti uvnitř konstrukce po přibližně jednom roce od dokončení stavby a započetí užívání objektů. Hlavním předmětem zájmu je porovnání především vlivu použití mokrých a suchých procesů uvnitř dřevostavby na vlhkost v konstrukci budovy.

Následující článek přináší návrh řešení jednoho z problémů dřevostaveb – zvýšené vlhkosti v konstrukci stavby. Systém Moisture Guard, který byl vyvinut na Univerzitním centru energeticky efektivních budov ČVUT v Praze, kontinuálně monitoruje vlhkost přímo uvnitř konstrukce a v případě zjištění nepřirozeného nárůstu této vlhkosti informuje uživatele o možném úniku kapaliny. Systém se instaluje do vytipovaných kritických míst konstrukce (kuchyně, koupelny, toalety, technické místnosti aj.) již během stavby. Skládá se z centrální vyhodnocovací jednotky a několika (cca deseti) jednotlivých senzorů spojených napájecí a komunikační sběrnicí. Ze znalosti umístění senzorů je pak systém schopen i přibližně lokalizovat místo úniku.

Článek popisuje jeden z nejdůležitějších faktorů omezující životnost dřevostaveb - vlhkost. Ukazuje, jaké jsou nejčastější příčiny a důsledky zvýšené vlhkosti v konstrukci dřevostaveb a jakými způsoby lze tuto vlhkost detekovat a měřit. Prezentuje jednu z možných metod pro kontinuální monitoring - metodu měření elektrického odporu a jeho následný převod na hodnotu vlhkosti. Dále popisuje možnosti korekce této hodnoty na vliv teploty i na druh materiálu.

Článek popisuje problematiku vlhkosti v dřevostavbách. Ukazuje, jaké mohou být příčiny a důsledky zvýšené vlhkosti v konstrukci a jakými způsoby lze tuto vlhkost měřit. Jako jednu z nejvhodnějších metod prezentuje metodu měření elektrického odporu a jeho převod na hodnotu vlhkosti. Dále jsou zde prezentovány možnosti korekce této hodnoty na vliv teploty a druh materiálu.

Článek popisuje systém senzorů vlhkosti ve dřevě Moisture Guard, který byl vyvinut na Univerzitním centru energeticky efektivních budov ČVUT v praze. Účelem systému je kontinuálně monitorovat stav vlhkosti dřevěné konstrukce budovy a v případě zjištění nepřirozeného nárůstu této vlhkosti informovat uživatele o možném úniku kapaliny.

Článek popisuje systém senzorů sloužících pro detekci zvýšené vlhkosti ve stavebních materiálech, především dřevě. Předpokladem je zabudování sítě senzorů do konstrukčních materiálů dřevostavby a jejich připojení k monitorovací jednotce. Cílem je vyvinout sběrnicový typ senzoru vhodný pro permanentní zabudování do konstrukce již při realizaci stavby. Takový senzorový systém pak umožní včasnou a rychlou detekci zvyšující se vlhkosti a upozorní správce budovy. Primárně budou senzory rozmístěny v kritických místech budovy a v případě zvýšení vlhkosti upozorní na možné problémy. Tím lze přibližně lokalizovat místo vzniku poruchy, zkrátit dobu detekce a značně omezit rozsah i náklady na nutnou sanaci v případě havárie.

Následující článek popisuje systém senzorů sloužících pro detekci zvýšené vlhkosti ve stavebních materiálech. Předpokladem je zabudování sítě senzorů do konstrukčních materiálů dřevostavby a jejich připojení k monitorovací jednotce. Cílem je vyvinout sběrnicový typ senzoru vhodný pro permanentní zabudování do konstrukce již při realizaci stavby. Takovýto senzorový systém pak umožní včasnou a rychlou detekci zvyšující se vlhkosti a upozorní správce budovy. Primárně budou senzory rozmístěny v kritických místech budovy a v případě zvýšení vlhkosti upozorní na možné problémy. Tím lze přibližně lokalizovat místo vzniku poruchy, zkrátit dobu detekce a značně omezit rozsah i náklady na nutnou sanaci v případě havárie.

This paper deals with measurement of phase and ratio errors of current and voltage channels of a new produced energy meter. This fully digitally controlled energy meter combines the classical static energy meter with power quality analyzer. The calibration of phase and ratio errors in wide frequency range is then necessary. Paper shows the results of error measurement, introduces the mathematical approximations and describes the calibration constants. It allows error compensation and power calculation of particular harmonics. The electric power of the higher harmonics can be interesting information of distributed electric energy quality.

This article deals with wide frequency range behaviour of DC tolerant current transformers that are usually used in modern static energy meters. In this application current transformers must comply with European and International Standards in their accuracy and DC tolerance. Therefore, the linear DC tolerant current transformers and double core current transformers are used in this field. More details about the problems of these particular types of transformers can be found in our previous works. Although these transformers are designed mainly for power distribution network frequency (50/60 Hz), it can be interesting to understand their behaviour in wider frequency range. Based on this knowledge the new generations of energy meters with measuring quality of electric energy will be produced. This solution brings better measurement of consumption of nonlinear loads or measurement of non-sinusoidal voltage and current sources such as solar cells or fuel cells. The determination of actual power consumption in such energy meters is done using particular harmonics component of current and voltage. We measured the phase and ratio errors that are the most important parameters of current transformers, to characterize several samples of current transformers of both types.

Paper deals with effect of half-wave rectified current on the measurement in energy meter. This type of current can be normally present in distribution network and does not cause any problem in active energy consumption measurement. On the other hand it can be the cause of saturation of the high permeability core of dual core current transformers. Moreover half-wave rectified current brings the increasing of the reactive power and consequently also the apparent power. It causes rising of losses in the conductors. The simple energy meter, eg electromechanical, does not measure these values and the losses are hidden. In present day there are many problems with capacity of energetic distribution network. Therefore information about character of energy consumption can be very important.

Tester for a space micro-accelerometer was developed for pre-flight tests of the micro-accelerometer electronics.

The energy meters with dual core current transformers, that measure energy consumption of inductive or capacitive load and DC magnetic flux is present in the core, measure with the errors up to few tens of percentage. It is due to saturation of high permeability and it causes the step change of phase displacement. This change in dependence on the distance between permanent magnet and current transformer can be up to tens of degrees. The article deals with these errors and shows them in dependence on the type of load.

Current transformers can be very easily affected by dc component of measured current. The behavior of such transformers can be different in comparison with normal conditions. The errors of power measurements arise in order of units of percent and can be both positive and negative according to the type of load for some type of current transformers. The errors are mainly caused by change of phase shift between primary and secondary current. The source of the problem is dc magnetic flux in the ferromagnetic core of the current transformer. The presence of dc magnetic field in ferromagnetic core of current transformer can be, in some cases, detected by analyzing the frequency spectrum of current signal using a microcontroller, usually by measuring the second harmonic. According to these results the energy meter is able to decide about possibility of unauthorized current consumption.

This article deals with dual core current transformers that are used in some modern static watt-hour meters where they should substitute the more expensive DC tolerant current transformer with linear hysteresis loop. It describes the problem of power consumption measurement on inductive or capacitive loads where some DC magnetic field is applied. In this case the core with high permeability is saturated and operating point is moved on hysteresis loop of low permeability core. Then additional errors occur and the sign of the error can be both positive and negative depending on load type. Dimension of errors can be in order from units up to tens of per cents and it relies on power factor and DC magnetic field. Explanation of this problem is described in the article as well as some results of measurements and comparison with theoretical computation.

Micro-accelerometer MAC04 has been developed in order to measure very low accelerations such as those caused to satellites by atmospheric drag and other non-gravitational forces. The instrument uses a cubic proof-mass inside a small cavity. In an open loop the change of capacitance between the cube and 12 electrodes on the inner cavity surface is a measure of the applied acceleration. It is very difficult to ground test and calibrate such a device due to gravity. The tester simulates the change of capacitances (base capacitance 13,5pF, changes in a range of +-1.5pF). Complete closed loop system is presented.

AMR current measurement device is described. It works contactless with 1% accuracy.

The current transformers in modern static watt-hour meters have to fulfil the criteria according to international standards. The manufacturers of the transformers use various techniques to obtain high DC tolerance. Some of them use the cores with low permeability and narrow and almost linear BH loop. These transformers are quite expensive and therefore some manufacturers use the double cores made from high and low permeability material. But as was found these transformers could bring additional errors in special conditions. The paper describes these conditions and explains the problems.

The most of the electronic static energy meters employ current transformers for current sensing. The current transformer has to fulfil some requirements according to international standards. Accuracy, together with the immunity against the dc current, is one of the requirements. Therefore manufactures of energy meter use the dc tolerant current transformers with linear hysteresis loop. These types of sensors have constant parameters and behaviour in very wide range of dc biasing. Second type of current transformers employs two cores with different parameters. But the parameters and behaviour vary with dc biasing. This paper deals with the changes of phase error of current transformers under dc biasing and describes the consequences of these changes.

The precision of gastric motility and volume sensing by implanted magnetic sensors is sufficient for monitoring of the stomach volume.

This article introduces the current sensors that are used in electricity meters. It shows their advantages and disadvantages. This paper is especially focused on DC tolerant current transformers and how they can be influenced by the DC component of measured current. Moreover the effect of a strong magnetic field generated by permanent magnets is analysed. Method to eliminate the disturbance and the stealing of energy is then presented. Next, the article deals with Rogowski coils and how it can replace the current transformers in electricity meters. Finally the problem of manufacturing precise coils, suitable for measuring the current in order of tens mA as it is required by the distributors of electrical energy, is presented.

Gastric electrical stimulation has shown positive effects on weight reduction and on various gastric motility disorders. This stimulation leads to earlier satiety thus decreasing food consumption significantly. For long term effective function some control of implant activity is necessary, for which gastric volume and movements have to be sensed. For this purpose we have chosen mutual induction principle between small implantable coils. Sensors have to fulfill many requirements including biocompatibility, mechanical and chemical durability and minimum power consumption. First successful in-vivo experiments were held with simple configuration of two implantable coils and an external electronics box.

DC tolerant current transformers are used in modern electricity meters. This brings some advantages but at the same time increases ratio error and causes higher but almost constant phase displacement. Therefore it is important to measure both errors. The indirect method of these errors measurement the errors has been tested on a commercial DC tolerant current transformer with manufacturer declared errors and the calculated errors were in very good accord with the declared parameters. This way the verify of the indirect method was proven and it has been used for further measurements. The measurements have been done with four DC tolerant current transformers that use cores made by different manufacturers. This article describes the method of measurement and shows the results.

Two main errors exist in the current transformers: the ratio error and the phase displacement. These errors indirectly depends on apparent permeability of the ferromagnetic core. Precise current transformers usually use a core with high apparent permeability which ensures small errors. But even a small DC component of the measured current causes saturation of the core and growing errors. Therefore the cores with low permeability, narrow and almost linear hysteresis loop are used in the current transformers in the modern energy meters. This paper examines DC tolerance and its influence on the errors of the current transformer and describes the method of its measuring.

The current transformers are used in almost all energy meters. Therefore it is important to know about their ratio error and phase displacement. Two ways can be used for measurement both of the errors. The direct method consist in comparison of the measured current transformer with the standard current transformer. The indirect method uses a measurement of magnetizing current and computation the errors from its value. This article deals with the indirect method and its using with measurement on DC tolerant current transformers that are presently used in the energy meters.

On-demand gastric electrical stimulation has been proposed to save energy of the pacing implant. For the purpose of control enough information about movement and size of stomach has to be measured with minimum external parts. Higher long-term efficiency of the method is expected in addition to its formerly documented positive effects in obesity treatment. Magnetic induction principle was chosen to measure the elongation of gastric wall between attached coils. In vivo a simple two coil configuration has been successfully tested and satisfactory resolution in demanded bandwidth has been proved. Especially for experimental studies directional dependence may be compensated by multi-axial sensor.

Gastric electrical stimulation showed positive effects on weight reduction and on various gastric motility disorders. Up-to-date implantable device delivers uninterrupted pulse train, however that is not effective, furthermore forming a habit decreasing its efficiency gradually. Herein presented experimental measurement system for on-demand stimulation is designed to reduce the energy consumption dramatically. Magnetic induction principle was chosen to measure the elongation of gastric wall between attached coils. Experimental system was built and studies in vitro were made as well as in vivo experiments on laboratory animals. Biocompatibility of implantable parts had to be ensured. Multi-coil systems are planned to reduce the errors caused by angular deviations and transverse displacements in simple two coils arrangement. Series of developments have to be done to achieve fully implantable reliable device.

A device for the contactless current measurement with Anisotropic Magnetoresistive sensors (AMR) has been developed. As the AMRs are much more sensitive than classically used Hall sensors, no magnetic concentrator is needed. The realized device reaches so far the linearity error of ą60 ppm in the current range of ą11 A for DC, i.e. the absolute resolution is ą1.3 mA. And the error due to non-concentric wire is less then ą0.6 %. The influence of the external current is reduced more then 45 dB.