Measurements and Instrumentations

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Measurements and Instrumentations

• By Dr. Ghazi AL SUKKAR
• ghazi.alsukkar_at_ju.edu.jo

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Introduction-

• The field of measurements and instrumentation is
  rapidly changing where new Standards, Sensors and
  Measurement systems are continually being
  devised.
• IEEE transactions on instrumentation and
  measurement.
• Review of Scientific Instruments.
• Journal of Scientific Instruments.

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Begining of measurements-

• Barter trade ? they need to quantify the amounts
  being exchanged.

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Purpose of measurement system

• A measurement system is often made a part of a
  control system If you can not measure it, you
  can not control it .

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Measurement system (Instrument)Architecture-
Event ? Quantity (Variable)
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Sensor

• An element whose characteristics change with the
  change of in the Quantity Under Measurement
  (QUM).
• Ex Photo sensors, thermal sensors, strain
  gauges, motion sensorsetc.
• Primary Secondary Sensor.

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Signal Conditioning Element-

• Convert the output of the sensor to a more
  suitable form for further processing usually,
  voltage, current.
• Ex -Amplifier amplify voltage.
• -Deflection bridges convert impeadance change
  into voltage change.
• -Oscillator convert impedance change into
  frequency change.

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Signal Processing Element-

• Convert the output of signal conditioning element
  to a form suitable for presentation.
• Its mean purpose is the correction of the
  non-linearity in the sensor output signal.
• Ex A/D (ADC) converter, Microprocessor.

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Data Presentation Element

• Show the QUM in a form suitable for the observer.
• Ex -Pointer (Scale indicator).
• -Screen.
• -Printer.
• Sometimes one unit combines multi-elements.

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Standards Used in Measurements-

• The very first measurement units where those used
  in barter trade Based in whatever was available
  as a measurement unit, foot, hands, human
  fingures..etc.
• People lookforward to unify these means of
  measurement through put standards.
• Standards Instrument and techniques used to
  quantify variables.

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• Early establishment of standards for the
  measurement of physical quantities proceeded in
  several countries at parallel time, in
  consequence, several sets of units emerged for
  measuring the same physical variable.
• ex Length Yard,meter,mile
• Also tools and techniques used to quantify a unit
  have been progressively improved over the years.

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Ex Meter-

• 1. Defined as 10-7 times the polar quadrant of
  the earth.
• - Platinum bar made to the defined length was
  established as a standard of length in early
  nineteenth century.
• -Bar manufactured from a platinum-iridium
  alloy.
• 2. In 1960 redefined meter in term of 1.65076373
  x 106 wavelengths of radiation from krypton-86 in
  vacuum.
• 3. In 1983 redefined as the length travelled by
  light in an interval of 1/299792458 sec.

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Classification of standards-

1. International standards defined by international
   agreement and kept at the International Bureau
   of Weights and Measures in Sèvres, France.
2. Primary Standards Calibrated from International
   Standards and maintained in national standards
   laboratories in countries around the world.
3. Secondary Standards Calibrated from the Primary
   Standards, used in industry and research labs on
   a daily basis.
4. Working Standards.

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SI Units Systèmes Internationales dUnités -

• Define 7 base unites
• Length meter (m)
• Mass kilogram (kg)
• Amount of substance mole (mol)
• Time Seconds (sec)
• Temperature kelvin (K)
• Current ampere (A)
• Luminous intensity Candela (Cd)
• Other units are derived from the base units
• ex area m2
• speed m/s
• luminance Cd/m2