 Real versus nominal value

For the distinction between real purchasing power and money value, see Real versus nominal value (economics).
The distinction between real value and nominal value occurs in many fields. From a philosophical viewpoint, nominal value represents an accepted condition which is a goal or an approximation as opposed to the real value, which always is actually present. Often a "nominal" value is "de facto" rather than an exact, typical, or average measurement.
Contents
Measurement
See also: Nominal sizeIn measurement, a nominal value is often a value existing in name only^{[1]}; it is assigned as a convenient designation rather than calculated by data analysis or following usual rounding methods. The use of nominal values can be based on de facto standards or some technical standards.
All real measurements have some variation depending on the accuracy and precision of the test method and the measurement uncertainty. The use of reported values often involves engineering tolerances.
One way to consider this is that the real value often has the characteristics of an irrational number. In realworld measuring situations, improving the measurement technique will eventually begin yielding unpredictable least significant digits. For example, a 1 inch long gauge block will measure to be exactly 1 inch long until the measuring techniques reach a certain degree of precision. As techniques improve beyond this threshold, it will become clear that 1 inch is not the real value of the gage block length, but some other number that is always out of reach.^{[citation needed]}
Engineering
In various subfields of engineering, a nominal value is one for which the "name" for the value is close to, but not the same as, the actual value. Some examples:
 For dimensional lumber in North America, a "two by four" is not 2 inches by 4 inches, but rather between 1⅜ and 1⅝ inches thick and between 3⅜ and 3⅝ inches wide, sized to the equivalent rough hewn piece of softwood for nominal structural design purposes. The ⅛inch tolerances absorb the natural variation and cannot be reduced without risk.
 Mains electricity is nominally 230 V in the European Union, but is allowed to vary ±10%. In North America, the nominal voltage is 120 V, with variance allowed from 114 V to 126 V (±5%). Voltage is also supplied at 208 V, 240 V and 480 V with similar tolerances. In general, electrical devices are designed to work with one nominal voltage, which represents a band of possible actual voltages, power factor and AC waveform shapes.
 A machine is designed to operate at some particular condition, often stated on the device's nameplate. For example, a pump is designed to deliver its nominal pressure and flow while operating at its nominal speed and power. Actual operating conditions may vary.
 NiMH and NiCd rechargeable batteries have a nominal voltage of 1.2 V, but will actually supply real voltages ranging from about 1.45 V to 1.0 V during discharge.
Other cases involve diameter, speed, and volume.
Sometimes the word "nominal" is also used in engineering contexts as a synonym for "normal" or "expected"; for example, The rotor resistances on all the other operating wheels are nominal.^{[2]}
See also
Notes
 ^ ASTM D3039, D4139, and others
 ^ "Rear Wheel Trouble Continues". JPL. 20091210. http://jpl.nasa.gov/news/news.cfm?release=2009191&icid='NewsFeaturesHome'. Retrieved 20091210.
Categories: Engineering concepts
Wikimedia Foundation. 2010.
Look at other dictionaries:
Real versus nominal value (economics) — Economics … Wikipedia
Real GDP — is a macroeconomic measure of the size of an economy adjusted for price changes and inflation.Real GDP measures the output of final goods and services produced, and incomes earned at constant prices. Real GDP = [(Nominal GDP)/(GDP deflator)] x… … Wikipedia
Nominal terms — may refer to: Nominal terms (computer science) Real versus nominal value (economics) This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wi … Wikipedia
Nominal interest rate — In finance and economics nominal interest rate or nominal rate of interest refers to the rate of interest before adjustment for inflation (in contrast with the real interest rate); or, for interest rates as stated without adjustment for the full… … Wikipedia
Real interest rate — The real interest rate is approximately the nominal interest rate minus the inflation rate (see Fisher equation and below for exact equation). Since the inflation rate over the course of a loan is not known initially, volatility in inflation… … Wikipedia
Nominal (disambiguation) — A nominal is one of the parts of speech. Nominal may also refer to: Nominal aphasia, a problem remembering words and names Nominal category, a group of objects or ideas that can be collectively grouped on the basis of shared, arbitrary… … Wikipedia
Value (economics) — Economics … Wikipedia
Time value of money — The time value of money is the value of money figuring in a given amount of interest earned over a given amount of time. The time value of money is the central concept in finance theory. For example, $100 of today s money invested for one year… … Wikipedia
Inflation — This article is about a rise in the general price level. For the expansion of the early universe, see Inflation (cosmology). For other uses, see Inflation (disambiguation). Inflation rates around the world in 2007 … Wikipedia
Neutrality of money — is the idea that a change in the stock of money affects only nominal variables in the economy such as prices, wages and exchange rates, with no effect on real (inflation adjusted) variables, like employment, real GDP, and real consumption.[1]… … Wikipedia