Minerais de ferro do Ordovícico Inferior do Anticlinal de Valongo

The Lower Ordovician oolitic ironstones of Valongo anticline have abundant chamosite and/or siderite. True oolites are rare in the studied levels. Some pseudo-oolites are related to the presence of algae, as evidenced by cathodoluminescence. Iron came from emerged areas and deposited during transgression of Early Ordovician, in a shallow platform protected by barriers, with exhalativesedimentary vent in reducing environment rich in organic matte

Digital filtering in smart load cells

This paper describes an application of a Self Adaptive Pseudo-Moving Average Filter used in the implementation of a Smart Load Cell, to combine a stable digital output with a fast response to weight changes. The Smart Load Cell is a data acquisition solution using a single chip RISC microcontroller with very few other active and passive components around and taking advantage of the ratiometric functioning of load cell. The use of Smart Load Cells with digital outputs needs a cost effective in digital filtering of the final converter results for each Smart Load Cell. The technique is established by theoretical analysis and is justified by means of simulation and experimental results. The paper also describes an example of software calibration of a Multi-Load-Cells weighbridge, using four smart load cells.CEL-Cachapuz Electrónica Lda

Células de carga inteligentes

Este artigo descreve a implementaçãoo de uma arquitectura de procesamento de sinal das células de carga, muito simples, bastante eficaz e de baixo custo, desenvolvida em torno de um microcontrolador RISC e tirando partido da característica ratiomérica da saída das células de carga. Para amplificaçãoo e filtragem dos sinais aplicaram-se as técnicas de condensadores comutados. A necessidade de estabilidde térmica dos circuitos e componentes é minimizada devido ao uso da mesma cadeia de amplificação para o sinal e referência em conjunto com o software de calibração. A conversão analógico-digital é feita através do método de rampa simples, sendo controlado pelo microcontrolador que realiza todo o processamento digital necessário, bem como a comunicação série com o exterior. Também é descrito um exemplo de software de calibração duma plataforma de pesagem com várias células de craga "inteligentes"

On-chip integrated silicon bulk-micromachined soil moisture sensor with electronics and bus interface

This paper presents an on-chip silicon bulkmicromachined Soil Moisture Sensor (SMS) for irrigation control in greenhouses. The system-on-a-chip includes the SMS, readout electronics, self-test, calibration facilities and a digital bus interface for external data transmission. Moreover, this low-cost device can be applied in several locations (e. g. per each plant root), and networked together with the 1-wire bus. The heat-pulse technique is used (for measuring the maximum temperature on a distant point) to determine the volumetric heat capacity and hence the water content of a porous media, such as soil. In order to validate this method, experimental results were achieved with a macrosensor based on the heat-pulse and capacitance methods. The capacitance method relates the volumetric water content with the capacitance change (dielectric properties) of a probe, inserted in the soil. Several tests were performed for different type of soils and water contents. These results are compared with the measurements achieved using the conventional thermogravimetric method

A influência de variáveis ambientais no crescimento de espécies/procedências de Eucalyptus spp. nos estados de Minas Gerais e Espírito Santo.

Foram analisados onze experimentos de introdução de espécies e procedências potenciais de Eucalyptus instalados em várias localidades dos estados de Minas Gerais e Espírito Santo. O estudo da influência de variáveis ambientais dos locais de introdução no crescimento em altura dessas espécies, aos três anos e meio de idade, permitiu concluir que a altitude do local do experimento foi a variável que mais influenciou o crescimento em altura de Eucalyptus camaldulensis, E. dunnii, E. grandis, E. pellita e E. tereticornis; o déficit hídrico isoladamente influenciou significativamente apenas o crescimento em altura de E. urophylla; a temperatura média e o total anual de precipitações não influenciaram isoladamente o crescimento em altura das oito espécies estudadas, e que é possível prever o comportamento das espécies e procedências em relação ao crescimento em altura, conhecendo-se a altitude, déficit hídrico e total anual médio de precipitações do local de introdução

On-chip integrated silicon bulk-micromachined soil moisture sensor based on the DPHP method

This paper reports the design, modelling, fabrication and assembly of a silicon bulk-micromachined soil moisture microsensor using the Dual-Probe Heat-Pulse (DPHP) method. Soil humidity measurement is essential to studysoil preservation and control the development of plants, namely in closed ecosystem. The DPHP method uses a heater (Peltier effect) and a temperature probe (Seebeck effect) to determine the volumetric heat capacity of the soil and hence water content ( θv). This is the first time that the DPHP method is implemented in a microdevice and the first integrated sensor for soil moisture. This microdevice is more suited to measure at different soil depths in a non-destructive and automated manner.Agricultural and Agro-industrial Science and Technology Institute of the University of Trás-os-Montes and Alto Douro

Calibration of a multi-load cells weighing system based on neural networks

Multi-load cells weighting systems are based on a platform supported by four or more load cells, normally in parallel inputting lhe same signal conditioning unit. Because of mechanical and electrical paralleling tuning the gain of a load cell affects lhe behavior of the others, making the calibration difficult and tedious, specially withweightbridges for cars and trucb, requiring lhemotion of heavy weights around /arge p/atforms