Measuring instrument

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Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea
Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea
A Love Meter at a Framingham, Massachusetts Rest Stop.
A Love Meter at a Framingham, Massachusetts Rest Stop.

In the physical sciences and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the measurement results in a given number for the relationship between the item under study and the referenced unit of measurement. Measuring instruments and formal test methods are the means by which this translation is made. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty.

Physicists use a vast range of instruments to perform their measurements. These range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments.


Contents

[edit] Time

Timeline of time measurement technology


[edit] Mechanics

[edit] Length (i.e., distance)

  • Electronic distance meter
  • Ultrasound distance measure, indirect by runtime measurement of sound waves (sonar, Echo sounding)
  • Laser rangefinder, indirect by runtime measurement of coherent electromagnetic waves around the visible light region (lidar)
  • Radar antenna, indirect by runtime measurement of electromagnetic waves around the microwave region (radar)
  • GPS, indirect by runtime measurement of electromagnetic waves in the GHz-range

see also Distance measuring equipment

[edit] Area

[edit] Level

[edit] Volume

(if the mass density of a solid is known, weighing allows to calculate the volume)

[edit] Speed


[edit] Acceleration

[edit] Mass

[edit] Linear momentum

[edit] Force (current of linear momentum)

[edit] Pressure (current density of linear momentum)

Current density is also called flux.

Timeline of temperature and pressure measurement technology

[edit] Angle

[edit] angular velocity or rotations per time unit

[edit] Angular momentum

[edit] Torque



[edit] Electricity and Electronics

[edit] electric charge

[edit] electric current (current of charge)

[edit] voltage (electric potential difference)

[edit] electric resistance

[edit] electric capacitance

[edit] electric inductance

[edit] Energy carried by Electricity

[edit] Power carried by Electricity (current of energy)

These are instruments used for measuring electrical properties. Also see meter (electronics).

[edit] Electric Field (negative gradient of electric potential)


[edit] Magnetic Field


[edit] Thermodynamics

[edit] Temperature

  • Thermometer
  • Resistance thermometer principle: relation between temperature and electrical resistance of metals (platinum) (Electrical resistance), range: 10 kelvins to 1000 kelvins, application in physics and industry
  • Thermistors principle: relation between temperature and electrical resistance of ceramics or polymers, range: from about 0.01 kelvin to 2,000 kelvins (-273.14°C to 1,700°C)
unit overall range approximate precision
kelvin 0.01-2,000 row 1, cell 3
celsius -273.14-1,700 row 2, cell 3

[edit] Energy carried by Heat

This includes Thermal capacitance or temperature coefficient of energy, reaction energy, heat flow ... Calorimeters are called passive if gauged to measure emerging heat, for example from chemical reactions. Calorimeters are called active or heated if they heat the sample, or reformulated: if they are gauged to fill the sample with a defined amount of heat.

see Calorimeter or Calorimetry

[edit] Entropy transfer

Phase change calorimeter's energy value divided by absolute temperature give the entropy exchanged. Phase changes produce no entropy and therefore offer themselves as an entropy measurement concept. Thus entropy values occur indirectly by processing energy measurements at defined temperatures, without producing entropy.

  • constant-temperature calorimeter, phase change calorimeter

[edit] Entropy content

The given sample is cooled down to (almost) absolute zero (for example by submerging the sample in liquid helium). At absolute zero temperature any sample is assumed to contain no entropy (see Third law of thermodynamics for further information). Then the following two calorimeter types are used to fill the sample with entropy until the desired temperature has been reached: (see also Thermodynamic databases for pure substances)

[edit] Entropy production

Processes transferring energy from a non-thermal carrier to heat as a carrier produce entropy (Example: mechanical/electrical friction). Either the produced entropy or heat are measured (calorimetry) or the transferred energy of the non-thermal carrier may be measured.

  • calorimeter
  • (any device for measuring related work and ambient temperature)

Entropy lowering its temperature - without loosing energy - produces entropy (Example: Heat conduction in an isolated rod; "thermal friction").

  • calorimeter

[edit] temperature coefficient of energy ("heat capacity")

Concerning a given sample, a proportionality factor relating temperature change and energy carried by heat. If the sample is a gas, then this coefficient depends significantly on being measured at constant volume or at constant pressure. (The terminiology preference in the heading indicates that the classical use of heat bars it from having substance-like properties.)

[edit] specific temperature coefficient of energy ("Specific heat")

The temperature coefficient of energy divided by a substance-like quantity (amount of substance, mass, volume) describing the sample. Usually calculated from measurements by a division or could be measured directly using a unit amount of that sample.


[edit] Coefficient of thermal expansion

[edit] More on Condensed Matter, Gas

[edit] Amount of substance

usually determined indirectly by measuring volume, mass, molar concentration or "knowing particle number"


[edit] Plasticity of a solid

[edit] Tensile strength, Ductility or Malleability of a solid

[edit] Hardness of a solid

[edit] Shape and surface of a solid

[edit] Granularity of a solid or a suspension

  • Grindometer

[edit] Optical activity of a solid

[edit] Compressibility

[edit] Density

[edit] Substance Flow measurement

[edit] Substance potential or Chemical potential or molar Gibbs energy

The substance potential of a redox reaction is usually determined electrochemically using reversible cells.

[edit] Substance content in mixtures


[edit] pH: Concentration of Protons in a Solution


[edit] Humidity

[edit] Rays ("Waves" and "Particles")

[edit] Sound, compression waves in matter

[edit] Sound pressure

[edit] Light and radiation without a rest mass

(for lux meter see the section about human senses and human body)

[edit] Photon polarization

[edit] Pressure (current density of linear momentum)

[edit] radiant flux

The measure of the total power of light emitted.

[edit] Radiation with a rest mass, Particle radiation

[edit] Cathode Ray

[edit] Atom polarization and electron polarization


[edit] Ionizing Radiation

Ionizing radiation includes rays of "particles" as well as rays of "waves". Especially X-rays and Gamma rays transfer enough energy in non-thermal, (single) collision processes to separate electron(s) from an atom.

[edit] particle current

[edit] Human Senses and Human Body

[edit] concentration or partial pressure of carbon dioxide in the respiratory gases

[edit] power, work

[edit] luminuos flux, Photometry

A measure of the perceived power of light, luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

[edit] illuminance, Photometry

See also: Category:Physiological instruments


[edit] Meteorology

See also Category:Meteorological instrumentation and equipment.

[edit] Navigation

See also Category:Navigational equipment.

[edit] Uncategorized, Specialized application


[edit] Notes

Note that the alternate spelling "-metre" is never used when referring to a measuring device.

[edit] See also

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