Measuring Instruments

A measuring instrument is a device to measure 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.
Stopwatches 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.
*(see any measurement device for power below)

For the ranges of power-values see: Orders of magnitude (power).

Action

Action describes energy summed up over the time a process lasts (time integral over energy). Its dimension is the same as that of an angular momentum.
*A phototube provides a voltage measurement which permits the calculation of the quantized action ( Planck constant) of light. (See also Photoelectric effect.)

Geometry

Dimensions (size)

Length (distance)

* Length, distance, or range meter

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

Area

* Planimeter

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

Volume

*Buoyant weight (solids)
*Eudiometer, pneumatic trough (gases)
*Flow measurement devices (liquids)
* Graduated cylinder (liquids)
* Measuring cup (grained solids, liquids)
*Overflow trough (solids)
* Pipette (liquids)

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 (volume)

Angle

* Circumferentor
* Cross staff
* Goniometer
* Graphometer
* Inclinometer
* Mural instrument
* Protractor
* Quadrant
* Reflecting instruments
** Octant
** Reflecting circles
** Sextant
* Theodolite

Orientation in three-dimensional space

See also the section about navigation below.

Level

* Level (instrument)
* Laser line level
* Spirit level

Direction

* Gyroscope

Mechanics

This includes basic quantities found in classical- and continuum mechanics; but strives to exclude temperature-related questions or quantities.

Mass- or volume flow measurement

* Gas meter
* Mass flow meter
* Metering pump
* Water meter

Speed or velocity (flux of length)

*Airspeed indicator
*LIDAR speed gun
* Radar speed gun, a Doppler radar device, using the Doppler effect for indirect measurement of velocity.
*Speedometer
* Tachometer (speed of rotation)
*Tachymeter
* Variometer (rate of climb or descent)
* Velocimetry (measurement of fluid velocity)

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

Acceleration

*Accelerometer

Mass

* Balance
* Check weigher measures precise weight of items in a conveyor line, rejecting underweight or overweight objects.
*Inertial balance
* Katharometer
* Mass spectrometers measure the mass-to-charge ratio, not the mass, of ionised particles.
*Weighing scale

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

Linear momentum

* Ballistic pendulum

Force (flux of linear momentum)

* Force gauge
* Spring scale
* Strain gauge
* Torsion balance
* Tribometer

Pressure (flux density of linear momentum)

* Anemometer (measures wind speed)
*Barometer used to measure the atmospheric pressure.
* Manometer (see Pressure measurement and Pressure sensor)
* Pitot tube (measures airspeed)
* Tire-pressure gauge in industry and mobility

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

Angular velocity or rotations per time unit

* Stroboscope
* Tachometer

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

For the ranges of frequency see: Orders of magnitude (frequency)

Torque

* Dynamometer
* Prony brake
* Torque wrench

Energy carried by mechanical quantities, mechanical work

* Ballistic pendulum, indirectly by calculation and or gauging

Electricity, electronics, and electrical engineering

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 (or power) in elementary electrodynamics is calculated by multiplying the potential by the amount of charge (or current) found at that potential: potential times charge (or current). (See Classical electromagnetism and Covariant formulation of classical electromagnetism)

Electric charge

* Electrometer is often used to reconfirm the phenomenon of contact electricity leading to triboelectric sequences.
* Torsion balance used by Coulomb to establish a relation between charges and force, see above.

For the ranges of charge values see: Orders of magnitude (charge)

Electric current (current of charge)

* Ammeter
* Clamp meter
* d'Arsonval galvanometer
* Galvanometer

Voltage ( electric potential difference)

* Oscilloscope allows quantifying time-dependent voltages
* Voltmeter

Electric resistance, electrical conductance, and electrical conductivity

* Ohmmeter
* Time-domain reflectometer characterizes and locates faults in metallic cables by runtime measurements of electric signals.
* Wheatstone bridge

Electric capacitance

* Capacitance meter

Electric inductance

*Inductance meter

Energy carried by electricity or electric energy

* Electricity meter

Power carried by electricity ( current of energy)

* Wattmeter

Electric field (negative

gradient of electric potential, voltage per length)

* Field mill

Magnetic field

See also the relevant section in the article about the magnetic field.
*Compass
* Hall effect sensor
* Magnetometer
* Proton magnetometer
* SQUID

For the ranges of magnetic field see: Orders of magnitude (magnetic field)

Combination instruments

* Multimeter, combines the functions of ammeter, voltmeter, and ohmmeter as a minimum.
* LCR meter, combines the functions of ohmmeter, capacitance meter, and inductance meter. Also called ''component bridge'' due to the bridge circuit method of measurement.

Thermodynamics

Temperature-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 multiplying 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)

:A physical quantity introduced in chemistry; usually determined indirectly. If mass and substance type of the sample are known, then atomic- or molecular masses (taken from a periodic table, masses measured by mass spectrometry) give direct access to the value of the amount of substance. (See also Molar mass.) If specific molar values are given, then the amount of substance of a given sample may be determined by measuring volume, mass, or concentration. See also the subsection below about the measurement of the boiling point.
*Gas collecting tube gases

Temperature

* Electromagnetic spectroscopy
*Galileo thermometer
* Gas thermometer principle: relation between temperature and volume or pressure of a gas ( gas laws).
**Constant pressure gas thermometer
** Constant volume gas thermometer
*Liquid crystal thermometer
* Liquid thermometer principle: relation between temperature and volume of a liquid ( coefficient of thermal expansion).
**Alcohol thermometer
** Mercury-in-glass thermometer
*Pyranometer principle: solar radiation flux density relates to surface temperature ( Stefan–Boltzmann law)
*Pyrometers principle: temperature dependence of spectral intensity of light ( Planck's law), i.e. the color of the light relates to the temperature of its source, range: from about −50 °C to +4000 °C, note: measurement of thermal radiation (instead of thermal conduction, or thermal convection) means: no physical contact becomes necessary in temperature measurement ( pyrometry). Also note: thermal space resolution (images) found in thermography.
* Resistance thermometer principle: relation between temperature and electrical resistance of metals (platinum) (electrical resistance), range: 10 to 1,000 kelvins, application in physics and industry
* Solid thermometer principle: relation between temperature and length of a solid ( coefficient of thermal expansion).
** Bimetallic strip
* Thermistors principle: relation between temperature and electrical resistance of ceramics or polymers, range: from about 0.01 to 2,000 kelvins (−273.14 to 1,700 °C)
* Thermocouples principle: relation between temperature and voltage of metal junctions ( Seebeck effect), range: from about −200 °C to +1350 °C
*Thermometer
* Thermopile is a set of connected thermocouples
* Triple point cell used for calibrating thermometers.

Imaging technology

* Thermographic camera uses a microbolometer for detection of heat radiation.

See also Temperature measurement and :Thermometers. More technically related may be seen thermal analysis methods in materials science.

For the ranges of temperature-values see: Orders of magnitude (temperature)

Energy carried by entropy or thermal energy

This includes thermal mass 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.
*Actinometer heating power of radiation.
* Constant-temperature calorimeter, phase change calorimeter for example an ice calorimeter or any other calorimeter observing a phase change or using a gauged phase change for heat measurement.
* Constant-volume calorimeter, also called bomb calorimeter
* Constant-pressure calorimeter, enthalpy-meter, or coffee cup calorimeter
* Differential Scanning Calorimeter
* Reaction calorimeter

:See also Calorimeter or Calorimetry

Entropy

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.
* Constant-temperature calorimeter, phase change calorimeter
* Heat flux sensor uses thermopiles (which are connected thermocouples) to determine current density or flux of entropy.

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 active calorimeter types can be used to fill the sample with entropy until the desired temperature has been reached: (see also Thermodynamic databases for pure substances)
* Constant-pressure calorimeter, enthalpy-meter, active
* Constant-temperature calorimeter, phase change calorimeter, active

Entropy production

Processes transferring energy from a non-thermal carrier to heat as a carrier do produce entropy (Example: mechanical/electrical friction, established by Count Rumford).
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 the work which will or would eventually be converted to heat and the ambient temperature)
Entropy lowering its temperature—without losing energy—produces entropy (Example: Heat conduction in an isolated rod; "thermal friction").
*calorimeter

Temperature coefficient of energy or " 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.)
* Constant-volume calorimeter, bomb calorimeter
* Constant-pressure calorimeter, enthalpy-meter

Specific temperature coefficient of energy or " specific heat capacity"

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.

For the ranges of specific heat capacities see: Orders of magnitude (specific heat capacity)

Coefficient of thermal expansion

* Dilatometer
* Strain gauge

Melting temperature (of a solid)

* Differential Scanning Calorimeter gives melting point and enthalpy of fusion.
* Kofler bench
* Thiele tube

Boiling temperature (of a liquid)

* Ebullioscope a device for measuring the boiling point of a liquid. This device is also part of a method that uses the effect of boiling point elevation for calculating the molecular mass of a solvent.

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(ed) solids like crystals, in contrast to bulk density of grainy or porous solids.
* Aerometer liquids
* Dasymeter gases
*Gas collecting tube gases
* Hydrometer liquids
* Pycnometer liquids
* Resonant frequency and damping analyser ( RFDA) solids

For the ranges of density-values see: Orders of magnitude (density)

Hardness of a solid

* Durometer

Shape and surface of a solid

* Holographic interferometer
*Laser produced speckle pattern analysed.
* Resonant frequency and damping analyser ( RFDA)
* Tribometer

Deformation of condensed matter

* Strain gauge all below

Elasticity of a solid (

elastic moduli)

* Resonant frequency and damping analyser ( RFDA), using the impulse excitation technique: A small mechanical impulse causes the sample to vibrate. The vibration depends on elastic properties, density, geometry, and inner structures (lattice or fissures).

Plasticity of a solid

*Cam plastometer
* Plastometer

Tensile strength,

ductility, or malleability of a solid

* Universal testing machine

Granularity of a solid or of a suspension

*Grindometer

Viscosity of a fluid

* Rheometer
* Viscometer

Optical activity

*Polarimeter

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