José Miguel Dias Pereira

An overview and a contribution to the optical measurement of linear displacement

The present work is a contribution to the field of linear displacement measurements by optical means. For that purpose, a brief overview of some existing solutions is presented and two systems for axial linear displacement measurement based on light intensity detection are introduced. The systems have redundancy and were designed with the purpose of achieving identification and automatic correction of errors arising from inadvertent angular variations between the sensor and the light beam positions.

An FFT-based method to evaluate and compensate gain and offset errors of interleaved ADC systems

Interleaved analog-digital converter (ADC) systems can be used to increase the sampling rate for a given ADC implementation technique. In theory, the maximum sampling rate that can be achieved is limited only by the bandwidth and the practical limits related to the power and space of integrated circuits. In this paper, a solution to increase the sampling rate of a digitizing system based on interleaved ADCs is presented. An error analysis, which takes into consideration offset and gain errors of the different ADC channels, is performed in order to quantify the effect of such errors in the systems performance. A software method based on the fast Fourier transform is presented for offset and gain error compensation of interleaved ADC associations. Numerical simulations and experimental results are used to validate the theory and the proposed compensation algorithm.

Self organizing maps application in a remote water quality monitoring system

This work was developed in the context of a system for remote water quality monitoring based on a wireless local area network (WLAN) and includes a Kohonen self-organizing map (K-SOM) implementation in order to perform sensor data validation and reconstruction and sensor failure and pollution event detections. Simulation and experimental results are presented.

A Digitally Programmable A/D Converter for Smart Sensors Applications

Nonlinear analog-to-digital conversion in smart sensor applications is an important topic since signal digitization and linearization can be performed in a single step near the transducer. In this paper a double pulsewidth modulated (PWM) scheme for nonlinear analog-to-digital conversion is presented. Calibration or auto-calibration data stored in the smart sensors memory define the nonlinear profile characteristic of the transducer and provide the required data to obtain the inverse function of the analog-to-digital converter (ADC) transfer curve. Basically, as a function of the transducers nonlinearity degree, the input voltage range of the ADC is segmented in a continuous set of subintervals and, for each of these subintervals, a second-order correction term based on a PWM A/D conversion is used to obtain a linear characteristic for the smart sensor. Additional advantages of this method result from its easy implementation in low-cost microcontrollers that include generally comparator inputs and PWM outputs. A flexible and programmable A/D conversion solution can be dynamically adapted to variations of the transducers nonlinearity profile, and an increased resolution can be achieved at the expense of a lower conversion rate. Some MATLAB simulations and experimental results obtained with a square-root airflow transducer will be presented in the final part of the paper

The history and technology of oscilloscopes

Oscilloscopes are one of the main tools for analyzing electrical signals. The primary information obtained from the waveform of the signal is visualization of its amplitude variation over time. Oscilloscopes are excellent tools for testing, debugging, and troubleshooting because they can easily detect waveforms and demonstrate if the electrical components or circuit modules properly. The aim of this article is to provide an overview of the main characteristics of the different types of oscilloscopes and correlate their evolution with the development of the underlying technologies they incorporate

.NET Framework and Web Services: A Profit Combination to Implement and Enhance the IEEE 1451.1 Standard

In 1999, the 1451.1 standard, which defines a common object model and interface specification to develop open multivendor distributed measurement and control systems, was published. However, despite the well-known advantages of the model, there have been a few initiatives to implement a commercial version of the standard. In this paper, we describe the implementation of a network capable application processor (NCAP) in a well-known and well-proven infrastructure, i.e., the microsoft .NET framework. The use of a commercial framework increases productivity because it handles low-level programming details and provides good development tools, which allows us to produce a reusable and robust code. In addition, a solution to enhance the 1451.1 Standard is presented by proposing a new format for interNCAP communication based on eXtended Markup Language (XML) Web Services. This approach promotes interoperability because any device with a compatible Web Service middleware can locate and communicate with our prototype.

Smart walker solutions for physical rehabilitation

In the last decade, the clinical reasoning in physical therapy has been to develop systems for physiotherapists to make clinical decisions rapidly, effectively and efficiently, in response to the increasingly complex needs of health and rehabilitation units [1]-[3]. Some studies show the importance of walking aids during rehabilitation from some diseases, and after surgery for arthroplasty in the elderly population [4], and in elderly patients with balance disorders, muscle weakness [5] or in people with diabetes mellitus [6]. Walkers are important devices that aid the rehabilitation process. The use of a walker is recommended for gait changes and imbalance due to various factors, such as surgery of the lower limbs or neurodegenerative changes, especially in the early recovery period [7].

Data Fusion, Decision-Making, and Risk Analysis: Mathematical Tools and Techniques

Human activity involves sequential decision-making. Activities with alternatives require deciding for one of the alternatives. A rational decision is one that weighs each alternative pros, cons, and risks. The support for decision-making is data that come basically from experience, either previously acquired or gathered for the specific decision-making. The data usually come from different sources and thus have to be fused for a single decision. The core of this chapter is precisely about data fusion. In its subsections, we look namely at some procedures and techniques commonly used in data fusion. Decision-making and risk analysis are briefly discussed

HART protocol analyser based in LabVIEW

Analysis of highway addressable remote transducer (HART) protocol is important in reliability evaluation of HART based systems. We propose a virtual instrument based solution for HART signal analysis that includes a digital oscilloscope with GPIB interface, a HART modem, a PC with a GPIB interface board and a RS232 port, and a software component developed in LabVIEW. The HART analyser permits the visualisation of signals that correspond to the HART protocol, gives access to data coming from field instruments and has the ability to analyse and modify field instrument performance

FM-CW radar sensors for vital signs and motor activity monitoring

The article summarizes on-going research on vital signs and motor activity monitoring based on radar sensors embedded in wheelchairs, walkers and crutches for in home rehabilitation. Embedded sensors, conditioning circuits, real-time platforms that perform data acquisition, auto-identification, primary data processing and data communication contribute to convert daily used objects in home rehabilitation into smart objects that can be accessed by caregivers during the training sessions through human–machine interfaces expressed by the new generation of smart phones or tablet computers running Android OS or iOS operating systems. The system enables the management of patients in home rehabilitation by providing more accurate and up-to-date information using pervasive computing of vital signs and motor activity records.