Johann Nicolics

Magneto-optical rotational speed sensor

Abstract A new passive and wireless magneto-optical rotational velocity sensor is described. It is based on measuring the intensity oscillations of linearly polarized light transmitted through an orthoferrite plate and an analyzer. The plate is subjected to the action of the magnetic field of a disc whose angular velocity has to be measured. Thanks to the high velocity and smooth reproducible character of the domain wall motion in the orthoferrite plate, one can continuously measure angular velocities in a very wide range—from ultralow to the MHz range.

A Low-Cost Wireless Sensor System and Its Application in Dental Retainers

In this paper, a wireless interrogable sensor device based on an ultra low-power microcontroller for data collection and a radio frequency identification (RFID) interface for data transmission is presented. Wireless sensor systems utilizing RFID transponders offer a new and exciting means of measurement and identification suitable for many biomedical applications. For the majority of these applications, small, inexpensive radio request sensor systems are desirable. In this paper, an ultra-low-power and low-cost wireless temperature data logger system is presented with its application in observing dental retainer use. For this purpose, the retainers ambient temperature is measured by an integrated sensor and recorded using a microcontroller which acts like a temperature data logger storing the thermal history of several months. For a self powered wireless data transmission from the sensor to the interrogation unit a RFID transponder, operating in the 13.56 MHz ISM band, is used. The presented sensor system includes hard- and software power saving modes reducing the sensor idle current consumption to 1 muA. This allows a battery powered operation of the device for up to two years. For dental and biomedical applications, the device is hermetically sealed using a biocompatible polymeric encapsulation. Results of the first clinical trials observing the patients dental retainer usage by a set of retainers equipped with the RFID temperature sensor/data logger device are presented. The stored temperature values are analyzed and a clear temperature characteristic indicating the retainer usage was found.

Magneto-optical current sensors of high bandwidth

A new current transformer is described by means of new results concerning the domain wall excitation in orthoferrites. The measured parameter is the geometrical position of the boundary between domains with opposite magnetizations. In a wide frequency band, including DC currents, the measurement results are a linear function of the measured current due to the very high domain wall velocity. They are not affected by temperature changes and mechanical factors.

Wirelessly interrogable magnetic field sensor utilizing giant magneto-impedance effect and surface acoustic wave devices

A micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30 /spl mu/m diameter amorphous FeCoSiBNd wire of zero magnetostriction. Surface Acoustic Wave (SAW) devices are described as passive, radio requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors. In order to develop a wirelessly interrogable magnetic field sensor, the combination of GMI sensors and SAW transponders is discussed by several measurements. The device shows a relative signal sensitivity of 80 dB/T at low magnetic flux density B<30 mT, quick response (/spl ges/40 MHz bandwidth), and a high-temperature stability.

Latching type optical switch

An optical switch on yttrium orthoferrite crystal is developed. The switch is of latching type and has an operating time of 100 ns. Matrices of switches are feasible due to the dimensions of the optical rotator of less than 2 mm3.

Application of orthoferrites for light spot position measurements

Results of measurements of the light spot positions based on the spatial light modulation in an orthoferrite crystal are presented. The reproducibility of the measurements is 0.8 μm and the sampling rate is 600 kHz.

Magneto-optical current sensor by domain wall motion in orthoferrites

A brief review of the latest developments on optical current measurements based on the Faraday effect is presented. In all existing magneto-optical current transformers, the main measured parameter is the polarization state of the light transmitted by a sensor element. A new transformer is described by means of new results concerning the domain wall excitation. The measured parameter is the geometrical position of the boundary between domains with opposite magnetizations. In a wide frequency band, including DC currents, the measurement results are a linear function of the measured current. They are not affected by temperature changes and mechanical factors.

High resolution thermal simulation of electronic components

Abstract An efficient thermal management in electronic components is essential to minimize the influence of thermomechanically induced stress and thermal load. Frequently, thermal simulation tools are applied to reduce the number of experiments needed for thermal characterization of the semiconductor components. However, for using commercially available software packages, much effort is necessary for maintenance and for generating the thermal models. Moreover, the limitation of the node number does not allow a discretization sufficiently fine for more complex structures as in high lead count packages. In this paper, a new thermal simulation tool is presented, which allows one to create models in a very efficient way. The developed and implemented solver based on the alternating direction implicit method is efficiently processing the required high node number. Moreover, the developed thermal simulation tool is applied for the thermal characterization of a 176 lead quad flat pack (QFP-package) using a discretization with 320,000 nodes. Steady-state and transient thermal qualities of the package are investigated under boundary conditions as specified by the Joint Electronic Device Engineering Council (JEDEC). Further, results obtained by thermal simulation are compared with those established from experimental procedures. Conclusions of how this new tool can be used for thermal design optimization are derived.

Passive wirelessly requestable sensors for magnetic field measurements

A direction-sensitive micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30-μm diameter amorphous FeCoSiBNd wire. Consisting of a micro-sized zero-magnetostrictive amorphous wire of about 70-μm length, the GMI sensor was connected to a self-oscillating Colpitts oscillator circuit by laser welding. It shows a high sensitivity with a resolution of 100 nT for DC fields, quick response, and a high temperature stability. Reproducible measurements of a surface-flux distribution of mechanically 100 μm structured magnetic bar codes were carried out. Surface Acoustic Wave (SAW) devices are shown as passive, radio-requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors. In order to develop a wirelessly interrogable magnetic field sensor, the combination of the GMI sensors and SAW transponders is discussed and the results are shown.

Optimization of process parameters for laser soldering of surface mounted devices

The authors present characteristics of laser soldering the explain their importance for industrial application. The dependence of solder joint quality on the laser beam parameter settings as well as on the properties of the solder and the materials to be joined is discussed. A simple thermal model is used to describe the influence of material properties on the temperature within the solder joint. Temperature courses recorded during soldering processes while applying different parameter settings are analyzed. >