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Based on the experimentally discovered regularity – emission of micro-sized particles during monoaxial deformation of non-homogeneous structures, such as rocks and concretes, a sensor technology to identify their pre-destruction processes is proposed. At nearing the stressed state until the disintegration of the massifs, exponential increase of particles generation appears. The innovation is applicable to risky rock formations where vertical measurement boreholes are made, by which kernels are obtained. Using the specimens formed by the kernels, through monoaxial load by press in laboratory conditions and corresponding particle emissions, the reference pressure values for different stages of the pre-destructive state development are determined. The reference data from the pressure are compared with the results for the deformation loads in the rock structure, corresponding to the generated particles in a borehole model. The values of the stress determine the occurrence of critical states in the structure. This information is an integrated indicator for the timely identification of pre-destructive processes in rocks. The described system increases the accuracy of determining the appearance of failure conditions. One of the strategic applications of the new technology is in seismically active regions.

Regularity has been observed in the generation of microparticles during uniaxial deformation of rocks and building concretes with the following formula: a previously unknown phenomenon in solid non-regular structures has been experimentally established and investigated, which is expressed in emission of microparticles under the action of strong uniaxial pressures. The size and amount of the fine-dispersed microfractions depend on the substance’s physicalmechanical properties and pressure values. The paper presents the first results of the observed phenomenon in rock structures – granite and limestone originating from some regions of Bulgaria. The effect motivates the option for using the emission process as a new sensor method for assessment of the stress condition of solid-state systems.

A novel method and a device measuring the mobility of majority carriers in semiconductors using the Hall current is proposed and experimentally tested. The geometry of the mobility-determining structures is similar to the topology of the so-called Corbino disk. The semiconductor wafer, in our case, n-silicon, has circular form and two concentric ohmic contacts: one of them in the central zone of the disk, and the other around the circumference. In contrast to this well-known Corbino configuration, the peripheral electrode is interrupted, whereas the size of the so-formed arc is many times smaller than the remaining section of the external perimeter. The two ohmic contacts are brought together to a current source, and the external magnetic field is applied perpendicularly to the disk plane. The ends of the interrupted electrode are connected to an electronic galvanometer measuring the Hall current involved in the Corbino structure. The experiments were carried out at room temperature and in liquid nitrogen. The results obtained with the new device are comparable to the previously known mobility values.

An original multidimensional magnetic-field sensor using subsequent measurement method based on a bipolar drift-aided magnetotransistor is presented. The device contains silicon substrate, emitter, two base contacts and four collectors. Using a new effect consisting of electrical control of magnetosensitivity polarity, the full information about all components is obtained by three collector pair arrangements. The measurement is carrying out with the same magnetotransistor, but at different time. The channel sensitivities reach $\boldsymbol{\mathbf{S}_{\mathbf{x}} \approx 37.5 \mu \mathrm{A} / \mathrm{T}, \mathbf{S}_{\mathrm{y}} \approx 75 \mu \mathbf{A} / \mathbf{T}}$ and $\boldsymbol{\mathrm{S}_{\mathrm{z}}\approx 98\mu \mathrm{A}/\mathrm{T}}$ , respectively.

In this paper is experimentally determined a mechanism occurring in gradient magnetic field at two-collector bipolar magnetotransistors (BMT) when their collector currents are equal at induction B = 0. The effect represents a linear control of the sum of these currents by the gradient field. This phenomenon transform the BMT’s in magnetogradiometer sensor with high resolution. The experiments are carried out with prototypes realized by integrated silicon processes and innovative magnetomodular system featuring high and linear gradient. The sensitivity of BMT reaches S ≈ 300 μA/T for the selected operation mode. The maximal gradient obtained with new actuator system is 78 mT/mm. The results are very promising, as the magnetogradiometer further extends the functional possibility of BMT for sensor electronics and automation.

A silicon 2D multisensor measuring simultaneously and independently the in-plane components of the magnetic field is experimentally tested. The devise contains one central ohmic contact and symmetrically to it - two perpendicular to each other pair of ohmic contacts. The sensitivities of the two sensor channels in accordance with symmetry are equal, reaching $\mathrm{S}=25\ \mathrm{V}/\mathrm{AT}$ at $T=300\ \kappa$ and $\mathrm{S}=119\ \mathrm{V}/\mathrm{AT}$ at $T=77\ \mathrm{K}$ . The channel cross-sensitivity does not exceed 5% as the internal noise is of the $1/f$ type.

A novel silicon Hall device with geometry-enhanced sensitivity was fabricated and characterized. The magnetosensitivity was grows with the charge carrier density on the Hall sides. The shape of the edges on which the Lorentz force deflects the electrons has the form of isosceles acute triangles on whose corners the ohmic Hall contacts are formed. The sensors were realized based on n-Si wafers with ρ ≈ 7.5 Ω.cm. The obtained transducer efficiency is by about 20 % higher than the sensitivity of the usual with orthogonal activation Hall element from the same material and with the same input conditions. The new Hall configuration is very promising for low-field magnetometry and robotized surgery.

A novel in-plane sensitive Hall-effect multisensor is presented, in the active transducer region of which, two Hall voltages are generated independently. This is achieved by the original design and by the supply formed by two constant currents. The residual offset drift is about 140 times smaller than the drift of a single Hall device. The magnetosensitivity reaches $\mathrm{S}_{\mathrm{RI}}\approx170\mathrm{V}/\mathrm{AT}$ . The signal-to-noise ratio is increased, the measured minimal magnetic induction is $B_{\min}\approx 9\mu \mathrm{T}$ . These characteristics will have impact on quantum communication, and medicine.

A novel single-chip sensing device for measurement of two orthogonal magnetic-field components using a common transducer zone and, for the first time, containing four contacts, is presented. On a rectangular n -type silicon substrate, n + - ohmic planar contacts are implemented − two of them are elongated and serve as power supply, and the other two terminals, positioned in the middle of the region between the elongated ones, function as outputs. A proper coupling arrangement is used for obtaining the information about vector components B x (parallel to the supply contacts) and B z (perpendicular to the substrate). Actually, the 2D magnetometer integrates an in-plane sensitivе Hall element and a device with vertical magnetic-field activation. The sensor operation is determined by the direction of the individual parts of the curvilinear current trajectory and the Lorentz force deflection action on them. The 2D vector sensor interface circuitry in hybrid realization comprises three instrumentation amplifiers and a differential amplifier. Simple fabrication technology is applied, containing four masks. The effective spatial resolution volume is high, constituting about 90 × 60 × 40 μm 3 . The respective channel-magnetosensitivities without amplification reached: the lateral sensitivity S x ≈ 17 V/AT and the vertical sensitivity S z ≈ 23.3 V/AT. The channel cross-talk at induction B ≤ 1.0 T is no more than 3% and the lowest detected induction B min for the two-axis device at supply 3 mA over frequency range f ≤ 100 Hz is about 11 μT.

An original p+-n -p+ magnetotransistors for subsequent measurement of three orthogonal magnetic components using a common sensor region is presented. Collector coupling-arrangements are formed for obtaining the information about the full magnetic-field vector. The operation is determined by curvilinear trajectory of holes and Lorentz force deflection on them. The channel outputs are linear and magnetosensitivities reaches Sx≈25µA/T, Sy≈150µA/T and Sz≈345µA/T for device with accelerating field in the base. The cross-talk reaches about 3.0 % at inductionB ≤ 1T.

The paper presents a single-chip 3-D multidimensional bipolar $p-n-p$ transistor (BMT) sensor for subsequent measurement of the three orthogonal magnetic-field components using one and the same transducer region. Three successive collector coupling arrangements make two parallel-field and one orthogonal BMT devices. The respective sensitivities are $\mathbf{S}_{\mathbf{x}} \approx 37.5 \mu \mathbf{A} / \mathbf{T}, \mathbf{S}_{\mathbf{y} \approx 7} 5 \mathbf{\mu} \mathbf{A} / \mathbf{T} \text { and } \mathbf{S}_{\boldsymbol{z}} \approx \mathbf{1} 04 \mathbf{\mu} \mathbf{A} / \mathbf{T}$. The proposed approach employs the same element, but at different time. The subsequent measurement method makes it possible to obtain an unusually high resolution using one and the same zone.

A novel in-plane sensitive Hall arrangement consisting of two identical n-Si three-contact (3C) elements and realized in a common technological process, is presented. In the solution, the minimization of the offset and its temperature drift is achieved by cross-coupling of the outer device contacts. This terminals’ connection provides equalizing currents between the two substrates which strongly compensate the inevitable difference in the electrical conditions in the two parts of the arrangement. As a result, the residual offset of both integrated Hall elements at the output Vout(0) and its temperature drift are strongly minimized. The residual offset is about 160 times smaller than the single-configuration one. The obtained output voltage-to-residual offset ratio at sensitivity of SRI ≈ 98 V/AT is very promising, reaching 6 × 103 at temperature T = 40 °C and induction 1 T. As a result, increased metrological accuracy for numerous applications is achieved. For a first time through the novel arrangement a suppression of sensitivity in the presence of external magnetic field could be achieved in order to obtain permanent offset information. This is one of the key results in the Hall device investigation.

A novel coupling of a pair of identical two-contact (2C) magnetoresistors transformed into an in-plane sensitive Hall device is presented. The ohmic contacts are cross-linked, also adding a load resistor bridge, providing for constant current mode of operation and eliminating the inevitable parasitic offset. This silicon configuration, apart from its simplified layout, has linear and odd output voltage as a function of the magnetic field and current. The quadratic and even magnetoresistance in the two parts of this innovative device is completely compensated, which ensures high measurement accuracy alongside with identification of the magnetic field polarity. The experimental prototypes feature sensitivity of 110 V/AT. The mean lowest detected magnetic induction B at supply current of 3 mA over frequency range f ≤ 100 Hz at a signal-to-noise ratio equal to unity is Bmin ≈ 10 μT. Тhe high performance and the complete electrical, temperature and technological matching of the parts of this unusual Hall device make it very promising for many practical applications.

A new 2D (two-dimensional) in-plane sensitive Hall-effect sensor comprising two identical n-Si Greek-crosses is presented. Each of the crosses contains one central square contact and, symmetrically to each of their four sides, an outer contact is available. Outer electrode from one configuration is connected with the respective opposite contact from the other configuration, thus forming four parallel three-contact (3C) Hall elements. These original connections provide pairs of opposite supply currents in each of the cross-Hall structure. Also the obligatory load resistors in the outer contacts of 3С Hall elements are replaced by internal resistances of crosses themselves. The samples have been implemented by IC technology, using four masks. The magnetic field is parallel to the structures’ plane. The couples of opposite contacts of each Greek-cross are the outputs for the two orthogonal components of the magnetic vector at sensitivities S ≈ 115 V/AT whereas the cross-talk is very promising, reaching no more than 2.4%. The mean lowest detected magnetic induction B at a supply current Is = 3 mA over the frequency range f ≤ 500 Hz at a signal to noise ratio equal to unity, is Bmin ≈ 14 μT.

A novel single-chip 3-D multidimensional Hall device for subsequent measurement of the three orthogonal magnetic-field components using one and the same transducer zone is presented. The magnetometer includes n -Si microsensor and simple and reliable interface circuitry which contains power supply and original signal extraction and conditioning circuitry. In the 3-D microsensor, six ohmic planar contacts on silicon substrate are implemented. Two of them are used for power supply. The other four are used to obtain the full information about the magnetic field vector components, by three successive coupling arrangements realizing two in-plane sensitive and one orthogonal Hall effect devices. The proposed approach employs the same element, but at different time. The sensor operation is determined by the direction of individual parts of nonlinear carriers’ trajectory in the substrate and the Lorentz force action on them. The effective sensor minimum operational volume is 90 μm × 60 μm × 30 μm. The respective channel-magnetosensitivities consist S x ≈ 35 V/AT, S y ≈ 26 V/AT, and S z ≈ 18 V/AT, the channel cross-talk at induction B ≤ 1 T reaches no more than 3% and the lowest detected magnetic field of the three channels is about 10 μT in the frequency range f ≤ 10 2 Hz. The instrument ensures the measurement of the full magnetic field vector with rate 20,000 Hz and the output signal is in range [−5 V, 5 V].

A novel in-plane magnetosensitive double Hall sensor, consisting of power supply and two identical three-contact и-Si cross-coupled architectures, realized in common technology process, is presented. High magnetosensitivity as well as increased metrological accuracy is achieved. The residual offset is about 160 times smaller than the internal ones. The obtained output voltage-to-residual offset ratio at magnetosensitivity of 98 V/AT (T = 300 K) is very promising, reaching 7.5×103 at magnetic induction IT.

A novel Hall magnetometer using dynamic offset cancellation principle is presented. It consists from a single triangular silicon plate with three contacts and interface electronics. The proposed dynamic offset-cancelling measurement cycle includes three states. During each state, an external circuit is switched to the plate contacts in a certain way. This way, the direction of current flow through the Hall plate is changed from phase to phase. At the same time, the output voltage is measured. After averaging the obtained three voltages per a measurement cycle, the offset voltage cancelled and this way the offset-free Hall voltage is obtained. The obtained offset reduction factor is very promising, reaching 120–130. The Hall device sensitivity is about 25 V/AT.

A new three-axis magnetometer for both 3-D magnetic field sensing and contactless in-plane 360° absolute angle encoding has been developed. The magnetometer is based on the Hall effect and consists of a circular in-plane sensitive CMOS Hall-effect microsensor, biasing and signal conditioning circuits. The sensing device contains a narrow n-well ring with a chain of contacts positioned radial on the ring. The signal conditioning circuit gives two output analogue signals: a voltage Vz, proportional to the magnetic field component Bz, and a sine wave function Vxy(t). The magnitude of the in-plane magnetic field B(x,y) is directly proportional to the sine amplitude and the phase Ψ corresponds to the angle between the applied in-plane magnetic field and a reference direction.

Future integrated systems will benefit significantly from the progress in batch manufactured silicon sensors and signal processing techniques. Silicon technologies make possible to produce sensing microdevices combining maximal sensitivity, high accuracy and minimal design complexity. Smart sensors on the base of Vertical vector Hall effect devices offer a number of advantages including reducing mass, volume and power consumption; greater redundancy of system functions and simpler architecture. In view of these characteristics, it can be expected that such smart sensors will be used extensively wide if an adequate solution is found to reduce the design cost and simplify the electrical interface. Consequently, cost effective microsystems including vector magnetic sensors, circuits and eventually actuators can be fabricated. This paper presents a new approach in the field of signal processing for magnetic field sensors based on vertical Hall elements. A design example is illustrated specific problems and solutions associated with data converters and signal-processing functions for smart sensors.

This paper contributes to the development of in-plane sensitive Hall-effect configurations based on a new sensor concept. An original coupling of pairs of identical two-contact (2C) magnetoresistors transduce an in-plane magnetic field, i.e., parallel to the silicon chip surface into a Hall voltages by means of four-contact (4C) and eight-contact (8C) devices. Two different arrangements are accomplished – hybrid realization with a discrete resistor bridge and fully integrated implementation. The pair’s ohmic contacts of the magnetoresistors are cross-coupled and parallel connected. These configurations has linear and odd output signal as a function of the magnetic field and supply current. The quadratic and even magnetoresistance of innovative solutions is completely suppressed, which ensures high measurement accuracy alongside with identification of the magnetic field polarity. The experimental prototypes feature simplified technological fabrication, sensitivity about 100 V/AT, low output temperature drift and high linearity. The lowest detected magnetic induction at current of 3 mA over frequency range 5 Hz ÷ 500 Hz at a signal-to-noise ratio equal to unity is around 10–12 μT. A benchmarking of the characteristics was performed with both new configurations as well as with an in-plane sensitive four-contact Hall element with closed design. It is established that the new arrangements have advantage and confirms the innovativeness of the proposed concept. The complete electrical, temperature and technological matching of proposed Hall devices is very promising for many practical applications.

A previously unknown galvanomagnetic effect in semiconductors (conducting materials) within wide temperature range (77–300 K) has been experimentally observed, which is expressed by the appearance of magnetically controlled currents on the opposite lateral boundaries of structures between which Hall voltage is also generated. Surface currents are a linear and odd function of the strength and direction of both the bias current and the magnetic field – if the direction of the magnetic field or the supply current is reversed, the polarity of the surface current will also change. This unexpected surface phenomenon is a direct demonstration of the action of the Lorentz force on the moving charges in semiconductors. The discovered mechanism can enrich the possibilities for surface characterization and rapid determination of the main parameters in solids, such as conductivity type, carrier concentration and carrier mobility. The dependence of the surface current in solids on various nonelectrical quantities is useful for development of new types of sensors for pressure, light, chemical composition etc.

A novel Hall device with enhanced magnetosensitivity has been implemented and tested. For the first time the transducer efficiency of the Hall sensor is increased due to the growth of surface charge density on Hall boundaries by reducing the area of the edges on which the Lorentz force deflects the carriers. The original shape of the Hall sides represents an isosceles acute triangle on whose vertex the Hall contact is formed. Discrete structures with four terminals and a three-contact version are developed in n-Si wafers. The experimentally obtained sensitivity is about 18% greater than the efficiency of a standard Hall element made of the same material and with the same input conditions. The new Hall sensors allow IC realization and are very promising for magnetometry.

An innovative parallel-field double-Hall microsensor comprising a silicon substrate, four planar contacts providing simultaneously two supply inputs and two differential outputs and a voltage source is characterized. This device functionally integrates two Hall devices sharing the same transducer zone and activated by unique supply current. The magnetosensitivities are equal but opposite in sign consisting of 40 V/AT and the two offsets are low and nearly equal. A self-reduction of the residual offset and its temperature drift is achieved by appropriate conditioning circuit, subtracting the two output voltages. A drastic compensation of the offset and the drift of more than two orders within a wide temperature range ( − 40 ≤ T ≤ 80 ∘ C ) is obtained.

A new class of Hall microsensors with minimal design complexity was suggested and experimentally tested. The devices consisting in n-Si substrate and three n+-strip contacts only are sensitive to a magnetic field parallel to the chip surface. Using a reference voltage generating with a specific bridge circuitry, the linear Hall voltage is extracted and the quadratic geometrical magnetoresistance is fully compensated. The internal noise of the design with a Hall contact located outside the sensor active region is at least ten times smaller than those of the three-contact element with an inside placed output electrode. This leads to enhanced resolution reaching Bmin ap 35 muT. A three-terminal multisensors generating simultaneously and independently strongly asymmetric voltage to the magnetic field direction and a Hall signal were devised too. The devices performance proved undoubtedly that new three-contact sensors could compete with the other well-known vertical Hall elements.

A new amperometric mode of operation of bipolar magnetotransistor (AMOBMT) is studied both theoretically and experimentally. This mode is achieved without reverse-biasing of the collector junctions and by using the current between the two ‘floating’ collectors as an information signal. The output current is a linear and anti-symmetrical function of the applied magnetic field. AMOBMT has some advantages with respect to the conventional mode of operation of bipolar magnetotransistor which utilizes reverse-biasing of the collector junctions.

The experimentally observed new phenomenon in conducting materials – the magnetically controlled surface current was examined again with an original measuring method and new silicon samples. The obtained results corroborate very well with the previously acquired data. The proposed registration approach utilizes the nulling compensation technique guaranteeing full offset compensation in all operating modes. The connection of the Ettingshausen effect with the new effect is clear demonstrated. A novel pressure sensor using the surface current dependence on external mechanical strain is developed and tested. The output characteristics of this transducer are very well reproducible and are suitable for measurement technologies.

A framework for design of novel interfaces for Cloud compatible medical services called User Interface as a Service (UIaaS) is presented in the paper. The aim is to support seamless and ubiquitous health monitoring based on flexible and useful Cloud services for healthcare. The paper describes the methods and new interfaces for health monitoring that have recently been developed for the proposed framework. The influence of the new methods and technologies for future Cloud computing systems for healthcare is discussed.

A pilot interface system is developed for computer-aided diagnostic and interventional assistance of cardiologists based on clinical trials. The system includes optimized methods for processing and presentation of cardiological knowledge and data. The multimodal principle of the interface is based on know-how tests of a new magnetic microsensor for detection of catheter navigation in images from angiograms and intra-vascular ultrasound and on new investigations of the principle of operation of the electrocardiograph. The user interface includes interactive access to the clinical database and a cognitive approach to disease visualization.

The devices and microsystems for measuring magnetic fields have the unique ability to reveal realities that cannot be perceived by the human senses. These transducers, which measure magnetic fields in a range not less than 15 to 16 orders of magnitude and are universal in their applications, are in continuous development.This chapter discusses recent progress in the most frequently used magnetic-field microsensors and MEMS, which are perfectly compatible with microelectronic technologies, most of which are silicon technologies. Up-to-date results are analyzed and abundant information is presented about the following topics: physical mechanisms of the origin of magnetosensitivity,device designs, sensor characteristics and the methods for their determination, biasing and inter-face circuits, the means for performance improvement and overcoming the basic transducer limitations, the most current and prospective applications, anddevelopment trends. Ample references torelevantliterature are included for all modifications of Hall effect devices (orthogonal and parallel field); micromagnetodiodes; magnetoresistors (including feromagnetic versions such as giant magnetoresistance elements); microsensors based on AniBv semiconductors; MOSFET, bipolar, CMOS, unijunction,and split-drain magnetotransistors and related devices; carrier-domain magnetometers; functional multisensorsfor the magnetic field, temperature, and light; 2-D and 3-D vector microsystems for the magnetic field; and magnetogradiometers and digital stochastic magnetotransducers.

A novel three-axis sensor for simultaneous and independent magnetic-field components measurement based on the Hall effect has been implemented and tested. On the upper side of n-Si substrate, a 10 colonm deep rectangular- shaped p-ring sized 50 x 160 colonm2 has been formed. In the n-zone surrounded by p-well, through six ohmic contacts, two parallel-field Hall devices for in-plane BBx and BBy components registration and one orthogonal Hall element for Bz detection has been functional integrated. The 3D magnetometer has been fabricated using silicon planar technology. The experimentally obtained magnetosensitivities are Sx ≈ 41V/AT, Sy ≈ 43V/AT and Sz ≈ 49V/AT, the cross- sensitivity reaches no more than 3%, the non-linearity is 1–2%, the noise spectral density on all outputs at frequency f ≤ 1000Hz is of the 1/f type and the sensor detectivity is BBmin ≈ 21 colonT. The spatial resolution is 50 x 160 x 10μm3.

ActiveVessel is a new multimedia workstation that enables the visualization, acquisition, and handling of different medical image modalities onand off-line for cardiology purposes. The workstation implements image decompression and browsing, video acquisition, reproduction, and storage for intravascular ultrasound (IVUS) and angiogram (X-ray) analysis. A distinctive implementation feature is the automatic image reconstruction with intensive use of 2D and 3D deformable models (snakes). The interactive interface allows the user to ‘correct’ deviations of catheter path reconstruction. An important characteristic feature of ActiveVessel is the interactive mode of model correction via mouse dragging. A novel technical solution for catheter path reconstruction is the integration with a magneto-sensitive micro-device (MSMD) inside the catheter/ vessel for faster and safer minimal invasive surgical intervention. This paper gives the overview of the entire system, its basic new functionalities, and the proposed technical solution of integration of four sensor modalities in cardiovascular practice.