Senzori

INTRODUCTION

Sensors and transducers course treats:

- The characteristics and performances

- The construction

- The functioning and the utility of sensors based

systems in industrial robots domain and applications.

SENSOR AND TRANSDUCERS NOTIONS

The transducer represents an elementary unit able to

convert a physical non electrical variable into a variable

that can be evaluate electrically.

The sensor represents a system based on one or more

transducers able to convert a non electrical variable into

an electrical variable that can be use without any

processing in an automatic control system.

Applications of sensors

Sensors are present at the moment in almost all human

activities, starting from labour saving devices to

complex industrial processes.

In technique there are three main applications of

sensors:

Monitoring of processes and operations

Control of processes and operations

Experimental engineering analysis

1. Monitoring of industrial processes and

equipments

The sensors based monitoring systems are used to

visualize and represent the process parameters. Their

reading do not serve any control functions into process

or equipment.

The monitoring measurement system are simply

indicate the condition of the environment, process or

equipment.

In home application, water, gas, and electric meters keep

track of the quantity of the commodity used so that the

cost to the user may be computed.

2. Control of processes and operations

In the most important type of application for sensor

based measuring systems, the instrument serves as a

component of an automatic control system.

A functional block diagram illustrating the operation of

such a system is shown in the figure.

To control a variable using an automatic system is based

on the "feedback" scheme. It is first necessary to

measure the variable. The control system must

incorporate at least one measuring instrument.

Examples of automatic control of a process:

Home-heating system

The home-heating system is designed to control the

temperature (thermostatic control) in a closed

environment (room).

A temperature-measuring instrument (often a bimetallic

element) senses the room temperature. The

measurement information is used to control the

heating/cooling device in order to regulate the

temperature inside the room.

A single control system may require information from

many measuring instruments. Many industrial machines

and process controllers also utilise multi-sensor

measurement systems.

3. Experimental engineering analysis

In solving engineering problems of the systems, two general

methods are available: theoretical and experimental.

Theoretical analysis method:

- To decompose the system in component elements

- To write the equations for component elements

- To eliminate the intermediary variables

- To determine the general equation

The features of the theoretical method:

1. Often gives results that are of general use rather than for

restricted application.

2. Invariably requires the application of simplifying assumptions.

Will result a simplified "mathematical model" of the system. This

means the theoretically predicted behaviour is always different

from the real behaviour.

3. In some cases, may lead to complicated mathematical problems.