Wolfgang Schelter

GMR sensor scheme with artificial antiferromagnetic subsystem

A magnetoresistive GMR-sensor scheme is demonstrated and analyzed in which the hard magnetic layers are replaced by Artificial Antiferromagnetic Subsystems (AAFs). These consist of ferromagnetic layers antiferromagnetically coupled via interlayers. The magnetic rigidity of this AAF is improved by an order of magnitude compared to the individual magnetic layers. Operational field windows for 360/spl deg/-angle detectors 20 kA/m have been realized. The sensor signal /spl Delta//spl rho///spl rho/ is 6%. The temperature-operation range extends itself up to 150/spl deg/C. The angle resolution is 1/spl deg/.

Integrated pO2, pCO2, pH sensor system for online blood monitoring

Abstract A self-calibrating sample-taking sensor system for online p O 2 , p CO 2 and pH monitoring is presented. The system consists of a two-lumen catheter with a sensor flow-through cell, a pump unit with instrumentation and a personal computer. The sensor device is based on an integrated silicon chip containing chemically sensitive field-effect transistors (ChemFETs) with CMOS signal-processing and thin film electrode systems for potentiometric and amperometric transducers. In vitro measurements and animal studies with anaesthetized pigs show good correlation with standard analyzer equipment.

Online blood electrolyte monitoring with a ChemFET microcell system

Abstract A sample-taking sensor system for online pH and electrolyte monitoring of blood is described. The system consists of a two-lumen catheter with a ChemFET flow-through cell, a syringe pump unit with ChemFET instrumentation and a personal computer. Suitable operation of the pump unit allows the sensor to be calibrated every 2 min before each measurement. The blood sample volume withdrawn from the patient is on the order of 10 μl. Solvent polymeric membrane ISFETs serve as measurement sensors as well as reference sensors. For this purpose they are spatially separated by a flow-through channel where a liquid junction can be established between the calibration solution and blood. In this way the arrangement saves a conventional reference electrode with the bridge solution. In vivo experiments in pigs show a very good correlation between sensor and analyzer values. There was no blood clotting in the sensor system.

Industrial applications of magnetoresistive sensors

Abstract Magnetoresistive sensors are commonly used for determining data in rigid disk drives, angular or linear positions, currents and magnetic fields. The magnetic field itself is the quantity which will be measured and the desired information about position, angle, distance, number of turns, rotational speed, defect detection, pressure, moment of force and tactile strength can be evaluated from the strength or direction of the field.

Contactless potentiometer based on giant magnetoresistance sensors

We present a magnetic sensor based on the giant magnetoresistance (GMR) effect, which can be used as a contactless potentiometer. The sensor consists of a novel GMR sensor scheme with an artificial antiferromagnetic subsystem. The sensor gives a sinusoidal signal in dependence on the direction of a rotating external magnetic field Hrot. With two sensors in a planar setup, the whole 360° angle range can easily be covered. The amplitude ΔR/R of the signal is about 5%. The signal amplitude runs through a very flat maximum and changes only by 5% within a field range of about 4.4–27.2 kA/m. This large field range, the magnetic window (Hw), is the main advantage of this sensor compared to other magnetic sensor physical principles for contactless potentiometers. Therefore, large mounting tolerances and variations in the field strength of the rotating permanent magnet can be accepted. The temperature dependence of the sensor is linear both for the ground resistance (R0) and the signal amplitude (ΔR), allowing sim...

Combination of amperometric and potentiometric sensor principles for on-line blood monitoring

Abstract Low-cost disposable multiparameter chemical sensors not only require monolithic and hybrid integration of different sensors, but also a combination of different measuring principles within a small area of a silicon chip. Miniaturized sensors can be implemented using potentiometric ISFETs and three-electrode amperometric sensors. ISFET-transducers need a signal ground reference to the analyte which would shunt the counter electrode of a three-electrode amperometric oxygen sensor without an isolating membrane. The working electrode potential of the oxygen sensor is used as the signal ground reference for the ISFETs. Despite the fact that the working electrode potential is varied cyclically for the purpose of electrode regeneration, no interference between the different sensors occurs.

Monitoring of blood pO/sub 2/ with a thin film amperometric sensor

A sample-taking sensor system for online pO/sub 2/ monitoring of blood is described. The system consists of a two-lumen catheter with a thin-film amperometric sensor cell, a pump unit with instrumentation, and a personal computer. The planar three-electrode system is only covered by a hydrophilic pHEMA membrane to avoid alterations in the composition of any internal electrolyte solution. To overcome the problem of electrode poisoning, the surface of the working electrode is regenerated during the calibration mode of the calibration/measurement cycle. Animal studies have been performed with anaesthetized pigs. The comparison of the sensor values with blood gas analyzer data shows a curved but reproducible correlation.<<ETX>>

Photolithographic structuring of giant magnetoresistive CoCu multilayers

Abstract A manufacturing process for structuring giant magnetoresistive multilayers based on dry etching techniques is described. The samples were deposited on oxidized silicon with the sensitive areas varying in width between 5 and 100 μm. The structured multilayers exhibited magnetic properties in accordance with unstructured macroscopic control samples of 100 mm 2 total area.

A New Catheter for Quasi-Continuous Measurement of Arterial Partial Oxygen Pressure

Recently a catheter has been developed based on amperometric measurement principle for in vivo monitoring of PaO2. A study in pigs was performed to compare the cell with a standard method for measuring PaO2. The results show that the cell is capable to accurately measure PaO2.

A micro transmission cell for monitoring of oxygen saturation and hemoglobin concentration

Abstract Oxygen uptake and transport into cells are important mechanisms for metabolism. There is a demand for sensors which measure oxygen saturation ( Sa O 2 ) and hemoglobin concentration ( c Hb ) for automated monitoring systems. An ex vivo optoelectrical flow-through cell is connected to a catheter and a pump system, originally developed for a ChemFET measuring system. The system is in vitro calibrated and has been tested in vivo with anesthetized pigs. It is capable of monitoring Sa O 2 and c Hb with high accuracy and stability with an expected lifetime greater than monitoring periods experienced in intensive care.