Measuring instrument


A measuring instrument is a device for measuring a physical quantity. In the physical sciences, quality assurance, 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 process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty.
These instruments may 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.

Time

In the past, a common time measuring instrument was the sundial. Today, the usual measuring instruments for time are clocks and watches. For highly accurate measurement of time an atomic clock is used.
Stop watches are also used to measure time in some sports.

Energy

Energy is measured by an energy meter. Examples of energy meters include:

Electricity meter

An electricity meter measures energy directly in kilowatt hours.

Gas meter

A gas meter measures energy indirectly by recording the volume of gas used. This figure can then be converted to a measure of energy by multiplying it by the calorific value of the gas.

Power (flux of energy)

A physical system that exchanges energy may be described by the amount of energy exchanged per time-interval, also called power or flux of energy.
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For the ranges of power-values see: Orders of magnitude.

Action

Action describes energy summed up over the time a process lasts. Its dimension is the same as that of an angular momentum.
This includes basic quantities found in classical- and continuum mechanics; but strives to exclude temperature-related questions or quantities.

Length (distance)

For the ranges of length-values see: Orders of magnitude

Area

For the ranges of area-values see: Orders of magnitude

Volume

If the mass density of a solid is known, weighing allows to calculate the volume.
For the ranges of volume-values see: Orders of magnitude

Mass- or volume flow measurement

For the ranges of speed-values see: Orders of magnitude

Acceleration

For the ranges of mass-values see: Orders of magnitude

Linear momentum

: The principle of a mercury barometer in the gravitational field of the earth.

Pressure (flux density of linear momentum)

For the ranges of pressure-values see: Orders of magnitude

Angle

For the value-ranges of angular velocity see: Orders of magnitude
For the ranges of frequency see: Orders of magnitude

Torque

See also the section about [|navigation] below.

Level

Considerations related to electric charge dominate electricity and electronics.
Electrical charges interact via a field. That field is called electric field.If the charge doesn't move. If the charge moves, thus realizing an electric current, especially in an electrically neutral conductor, that field is called magnetic.
Electricity can be given a quality — a potential. And electricity has a substance-like property, the electric charge.
Energy in elementary electrodynamics is calculated by multiplying the potential by the amount of charge found at that potential: potential times charge.
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Electric charge

For the ranges of charge values see: Orders of magnitude

Electric current (current of charge)

See also the relevant section in the article about the magnetic field.
For the ranges of magnetic field see: Orders of magnitude

Combination instruments

-related considerations dominate thermodynamics. There are two distinct thermal properties: A thermal potential — the temperature. For example: A glowing coal has a different thermal quality than a non-glowing one.
And a substance-like property, — the entropy; for example: One glowing coal won't heat a pot of water, but a hundred will.
Energy in thermodynamics is calculated by multipying the thermal potential by the amount of entropy found at that potential: temperature times entropy.
Entropy can be created by friction but not annihilated.

[Amount of substance] (or mole number">Mole (unit)">mole number)

See also Temperature measurement and :Category:Thermometers. More technically related may be seen thermal analysis methods in materials science.
For the ranges of temperature-values see: Orders of magnitude

[Energy] carried by [entropy] or [thermal energy]

This includes thermal capacitance or temperature coefficient of energy, reaction energy, heat flow...
Calorimeters are called passive if gauged to measure emerging energy carried by entropy, 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 entropy.
is accessible indirectly by measurement of energy and temperature.

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.
The given sample is cooled down to absolute zero. At absolute zero temperature any sample is assumed to contain no entropy. Then the following two active calorimeter types can be used to fill the sample with entropy until the desired temperature has been reached:
Processes transferring energy from a non-thermal carrier to heat as a carrier do produce entropy.
Either the produced entropy or heat are measured or the transferred energy of the non-thermal carrier may be measured.
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Entropy lowering its temperature—without losing energy—produces entropy.
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 temperature coefficient of energy divided by a substance-like quantity describing the sample. Usually calculated from measurements by a division or could be measured directly using a unit amount of that sample.
For the ranges of specific heat capacities see: Orders of magnitude

[Coefficient of thermal expansion]

See also thermal analysis, Heat.

More on [continuum mechanics]

This includes mostly instruments which measure macroscopic properties of matter: In the fields of solid state physics; in condensed matter physics which considers solids, liquids and in-betweens exhibiting for example viscoelastic behavior. Furthermore, fluid mechanics, where liquids, gases, plasmas and in-betweens like supercritical fluids are studied.

[Density]

This refers to particle density of fluids and compact solids like crystals, in contrast to bulk density of grainy or porous solids.
For the ranges of density-values see: Orders of magnitude

[Hardness] of a solid

[Tensile strength], [ductility] or [malleability] of a solid

This section and the following sections include instruments from the wide field of :Category:Materials science, materials science.

More on electric properties of [condensed matter], [gas]

[Permittivity], [relative static permittivity], ([dielectric constant]) or [electric susceptibility]

Such measurements also allow to access values of molecular dipoles.

[Magnetic susceptibility] or [magnetization]

For other methods see the section in the article about magnetic susceptibility.
See also the :Category:Electric and magnetic fields in matter

[Substance potential] or [chemical potential] or molar [Gibbs energy]

conversions like changes of aggregate state, chemical reactions or nuclear reactions transmuting substances, from reactants to products, or diffusion through membranes have an overall energy balance. Especially at constant pressure and constant temperature molar energy balances define the notion of a substance potential or chemical potential or molar Gibbs energy, which gives the energetic information about whether the process is possible or not - in a closed system.
Energy balances that include entropy consist of two parts: A balance that accounts for the changed entropy content of the substances. And another one that accounts for the energy freed or taken by that reaction itself, the Gibbs energy change. The sum of reaction energy and energy associated to the change of entropy content is also called enthalpy. Often the whole enthalpy is carried by entropy and thus measurable calorimetrically.
For standard conditions in chemical reactions either molar entropy content and molar Gibbs energy with respect to some chosen zero point are tabulated. Or molar entropy content and molar enthalpy with respect to some chosen zero are tabulated.
The substance potential of a redox reaction is usually determined electrochemically current-free using reversible cells.
Other values may be determined indirectly by calorimetry. Also by analyzing phase-diagrams.
See also the article on electrochemistry.

Sub-microstructural">Microstructure">microstructural properties of [condensed matter], [gas]

See also the article on spectroscopy and the list of materials analysis methods.

Rays ("[wave]s" and "particles">Subatomic particle">particles")

Sound, compression waves in matter

s in general, sometimes their sensitivity is increased by the reflection- and concentration principle realized in acoustic mirrors.

Light and radiation without a [rest mass], non-ionizing">Non-ionizing radiation">non-ionizing

See also :Category:Optical devices

[Photon polarization]

The measure of the total power of light emitted.

[Radiation] with a [rest mass], [particle radiation]

[Cathode ray]

[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, collision processes to separate electron from an atom.

Particle and ray [flux]

This could include chemical substances, rays of any kind, elementary particles, quasiparticles. Many measurement devices outside this section may be used or at least become part of an identification process.
For identification and content concerning chemical substances see also analytical chemistry especially its List of chemical analysis methods and the List of materials analysis methods.

Substance">Chemical substance">Substance content in [mixtures], substance identification

Sight">Visual perception">Sight

Brightness: photometry">photometry (optics)">photometry

Photometry is the measurement of light in terms of its perceived brightness to the human eye. Photometric quantities derive from analogous radiometric quantities by weighting the contribution of each wavelength by a luminosity function that models the eye's spectral sensitivity. For the ranges of possible values, see the orders of magnitude in:
illuminance,
luminance, and
luminous flux.

[Loudness] in [phon]

[Normal [human body temperature|Body temperature]] or [core temperature]

Blood-related parameters are listed in a blood test.

power">Power (physics)">power, work">Mechanical work">work of [muscles]

See also: :Category:Physiological instruments and :Category:Medical testing equipment.

[Meteorology]

See also :Category:Meteorological instrumentation and equipment.

[Navigation] and [surveying]

See also :Category:Navigational equipment and :Category:Navigation.
See also Surveying instruments.

Astronomy

See also Astronomical instruments and :Category:Astronomical observatories.

Military

Some instruments, such as telescopes and sea navigation instruments, have had military applications for many centuries. However, the role of instruments in military affairs rose exponentially with the development of technology via applied science, which began in the mid-19th century and has continued through the present day. Military instruments as a class draw on most of the categories of instrument described throughout this article, such as navigation, [|astronomy], optics and imaging, and the kinetics of moving objects. Common abstract themes that unite military instruments are seeing into the distance, seeing in the dark, knowing an object's geographic location, and knowing and controlling a moving object's path and destination. Special features of these instruments may include ease of use, speed, reliability and accuracy.

Uncategorized, specialized, or generalized application