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Brinksmeier E.,IWT - Foundation Institute of Materials Engineering | Heinzel C.,IWT - Foundation Institute of Materials Engineering | Wilkens A.,IWT - Foundation Institute of Materials Engineering | Lang W.,Institute for Microsensors | Seedorf T.,Institute for Microsensors
Advanced Engineering Materials | Year: 2010

A different to conventional monitoring systems sensor equipped tools give the possibility to gain information about the process status directly from the contact zone between tool and component to be machined. For example this can be realized by the integration of small temperature sensors into grinding wheels. The transmitting of the process data is performed by a telemetric unit attached to the grinding wheel's core. In this paper, the development of a new thin film thermocouple sensor concept is described. The unique feature of this sensor is the continuous contacting of the thermocouple through the grinding process inherent wear which leads to smearing of the thermoelectric layers and thus forming the measuring junction of a thermocouple. The system was used in OD grinding processes aiming to detect grinding burn and process instabilities. By reducing the volume of the sensors a fast response and high time resolution can be obtained. By thisway, observance of the key parameters of the practical operation as closely as possible to the cutting area is enabled and so observance of process efficiency and tool status independent from workpiece machining conditions can be realized. All sensors used are thermocouples of type K, a combination of Chromel (NiCr) and Alumel (NiAlMnSi) material. The maximum temperature to be measured by this sensor is about 1350 °C, which ensures the applicability in the grinding process. Telemetry components to amplify and send the thermovoltage signals are adjusted to this type of thermocouple. The ability of the set-up to detect thermal influences was demonstrated in grinding processes with a continuously increasing specific material removal rate. The approach serves to measure temperatures between fast sliding surfaces in harsh environments (fluids, high pressure, heat), similar to the grinding process. Therefore their application is not limited to tools but also applicable for other rotating components such as bearings, gears and shafts in powertrains. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jedermann R.,Institute for Microsensors | Jedermann R.,Microsystems Center Bremen | Potsch T.,University of Bremen | Potsch T.,Bremen Research Cluster for Dynamics in Logistics LogDynamics | And 2 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

Remote measurement of product core temperature is an important prerequisite to improve the cool chain of food products and reduce losses. This paper examines and shows possible solutions to technical challenges that still hinder practical applications of wireless sensor networks in the field of food transport supervision. The high signal attenuation by water-containing products limits the communication range to less than 0.5m for the commonly used 2.4GHz radio chips. By theoretical analysis of the dependency of signal attenuation on the operating frequency, we show that the signal attenuation can be largely reduced by the use of 433MHz or 866MHz devices, but forwarding of messages over multiple hops inside a sensor network is mostly unavoidable to guarantee full coverage of a packed container. Communication protocols have to provide compatibility with widely accepted standards for integration into the global Internet, which has been achieved by programming an implementation of the constrained application protocol for wireless sensor nodes and integrating into IPv6-based networks. The sensor's battery lifetime can be extended by optimizing communication protocols and by in-network preprocessing of the sensor data. The feasibility of remote freight supervision was demonstrated by our full-scale 'Intelligent Container' prototype. © 2014 The Author(s) Published by the Royal Society.

Sklorz A.,Institute for Microsensors | Lang W.,Institute for Microsensors
Procedia Engineering | Year: 2011

Three sensitivity improvement strategies for non-dispersive-infrared (NDIR) ethylene gas detectors were defined and examined: the application of low-cost Fresnel lenses, usage of a conically shaped measurement chamber and a simple digital signal processing lead to a seven times better IR-radiation efficiency compared to a system configuration without consideration of these methods. The approaches don't affect IR-detectors, IR-sources or the optical pathway and thus, the methods can be called "passive". It was shown that usage of lock-in amplifiers is not necessary to achieve good sensitivity results and noise equivalent concentrations of about 6 ppmv. © 2011 Published by Elsevier Ltd.

Breede A.,Faserinstitut Bremen e.V. | Moghaddam M.K.,Institute for Microsensors | Brauner C.,Faserinstitut Bremen e.V. | Lang W.,Institute for Microsensors | Herrmann A.S.,Faserinstitut Bremen e.V.
Materials Science Forum | Year: 2015

An online monitoring scheme to determine viscosity and permeability for a composite main spar infusion is presented. During the manufacturing process, defects such as dry spots and pores can occur and lead to poor part quality. In this study, dielectric sensors are used to create the information needed to model the process. Several experiments have been carried out to investigate the correlation between the sensors signal and the viscosity and to derivate constitutive equations. The provided data and the derived permeabilities are integrated into a simulation model of a cross section of the composite main spar. As a result, the real permeability can be identified. The knowledge of these parameters is one of the key aspects for a prediction of the resin flow and therefore for an improved process control. © (2015) Trans Tech Publications, Switzerland.

Kahali Moghaddam M.,Institute for Microsensors | Breede A.,Faserinstitut Bremen e.V. | Chaloupka A.,Fraunhofer Institute for Chemical Technology | Bodecker A.,Institute for Microsensors | And 4 more authors.
Sensors and Actuators, A: Physical | Year: 2016

In this study, microscale interdigital capacitive sensors are designed, fabricated and embedded in glass fiber composite for real-time cure monitoring of resin. The microscale interdigital capacitive sensor offers great advantages due to its miniaturized size, high flexibility and high temperature stability. Most importantly, after integration, due to the small footprint and only 5 μm thickness, the embedded sensor minimally downgrades the composite mechanical properties. Apart from all these merits, the substrate foil is perforated to provide an opportunity for the resin to go through the substrate and bridge it. The sensor consists of two interdigitated arrays. There are two different sensor designs, which offer 900 and 450 electrodes in arrays. The electrodes are made out of tantalum and are fully insulated with about 50 nm tantalum oxide. Therefore, it is possible to embed the sensor even in conductive fibers, e.g. carbon, and to use the sensor out of the Cleanroom without getting contaminated with conductive particles to shortcut the arrays. Polyimide is chosen for the substrate of the sensor. This specific polymer has excellent flexibility and its geometry stays unchanged even at high temperature. The Dielectric Analysis (DEA) measurement proves the effective and real-time tracking of resin polymerization during laminate production. © 2016 Elsevier B.V. All rights reserved.

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