Sensors and their Application for Disabled and Elderly People

Introduction

New technologies are a valuable instrument to mitigate the disabled and elderly people problems. When we speak about the disability concept (Ferreira, 2007), we refer to the fault of capacity or difficulty to carry out an activity that is considered as normal.

There are some statistical studies published that give the number of people that suffer some kind of disability. It is really surprising; according to the Statistical National Institute (INE), 8.5% (3,847,900 people) of the Spanish people declare to have some disability. In addition, more than 1.3 million need some kind of help to carry out the basic activities in their daily life. More than 60,000 are children and adolescents (INE, 2008).

The illnesses that can affect and hinder the disabled people to accomplish their daily activities can be classified according to their nature. We distinguish the following ones:

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  Sensory illnesses: That mainly affect the visual and auditory system and frequently it can reduce the tact sense.

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  Physical illnesses: That it usually affects the movement and body coordination, organic illnesses.

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  Metabolic and viral illnesses and cardiopathies among others are included.

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  Mental and psychiatric illnesses.

The use of new technologies to develop devices for disabled and elderly people is being quite important. Our purpose, along the following pages, is to present different types of sensors and the way to process and amplify their signals. We will also show some commercial references in order to introduce the reader to the topic and analyze the circuits needed to sense the environment to facilitate the live for disabled and elderly people.

What Is A Sensor?

A sensor is a device, formed by sensitive cells, that transforms physical or chemical magnitudes (instrumentation variables) in useful signals to measure or control systems (electric magnitude). The instrumentation variables depend on the type of sensor and they can be temperature, distance, acceleration, inclination, displacement, pressure, humidity, pH, etc. The electric magnitude can be a value of electric resistance, an electric capacity, a voltage, an electric current, etc. A transducer and a sensor are different devices and they should be differentiated. A transducer is a device that transforms a physical magnitude into a different physical magnitude (such as mechanical energy or electric energy). A transducer can be a microphone that transforms an audio wave into an electric signal. A sensor is a device that provides an output signal, given by a specific physical quantity. The input value is called measure magnutude and it causes an answer in the sensor. An example is a linear variable differential transformer (LVDT), which converts a position into an electric signal (Nyce, 2004). Therefore a sensor can be considered as a transducer and vice versa. All sensors can be classified and included inside of one of the groups shown in Table 1.