• Introduction
  • Prerequisites
  • Bibliography
  • Sensors Package

    The Instrumentation & Sensors Package is designed in order to emphasise the role of measurement in all technical activities.

    Measurement is at the basis of a lot technical activities because a main part of actions is done after an observation of the environment ; so in the technical world sensors are so called " weak link " because, in Control System, a lot of decision are based on measurement information provided by sensors, as show bellow.

    To discover the road of information in a Control Loop, please click on the blue arrow bellow.

    Click here for a simulation

    To discover the "road" of information within a Control Loop, please click on the blue arrow ; the loop scheme is on the basis of Automation, as far as Real Control Loop are concerned such

    (if you know a very interesting use of sensor, please let me know)

     

    So, sensors are essential for the industrial word, they allow

     

    (if you know other very interesting use of sensor, please let me know)

     

    They are also essential in your life, because with the help of sensors, your are able

    (if you know other very interesting use of sensor, please let me know)

     

    BUT

    as a postulate, you have to remember that a sensor gives to the end-user a information which is only an estimation of a the value of a physical quantity.

    Because of the used technologies and because of the measurement environment, the error between the "true" measure and the "delivered" measure could be represented by a randomised noise.

    The simulation below tries to illustrate this concept, please enter a number in the green box, and have a look on the value of the Produce Measure, and on the sign of the error.

    Click here for a simulation

    Notice that

    But, be confident, the sensor designer and the sensor manufacturer should do their best to make sure that this gap will be as close as possible…

    This gap is usually called uncertainty of measurement.

    Because the uncertainty between "true" measure and the "delivered" measure should always be specified, in association with the numerical value of the measure, the estimation of this uncertainty requires the use of mathematical tools and the process for evaluation is defined by some guidelines.

    So, a the result of a measurement should be

    Unit(s)

    The unit (of measurement) is a specific quantity, adopted by convention, used to express quantitatively quantities which have the same dimension

    SI (courtesy of the NIST)

    SI (courtesy of the BIPM)

    Sensors are very important

     in the industrial world,

     to measure level in silos , for instance

     to detect meteorological conditions ,

     in your "driver" live , you use "human" sensors along the road,

     to preserve a 500-year-old Peruvian mummy ,

     to determine the kinematics of the Mars Pathfinder Lander ,

     to measure human life parameters ,

     …

    But, in order to use the right sensor for the right application, some knowledge should be acquired ; it's the aim of this Metrology sub-package…

    To know

     what a sensor is,

     what are its qualities,

     what are (sources of) measurement errors,

     how some of them work,

     

    in order to use it in the best conditions and

    to verify if you acquire good knowlege about sensors terminology

    Before going further, please verify your knowledge about basis on Physics and Electronics

     


    Updated July 2000