| NCSA: National Center for Supercomputing Applications.
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| NEC: National Electric Codes. |
| Negative Temperature Coefficient: A decrease in resistance with an increase in temperature. |
| NEMA-12: A standard from the National Electrical Manufacturers Association, which defines enclosures with protection against dirt, dust, splashes by non-corrosive liquids, and salt spray.
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| NEMA-4: A standard from the National Electrical Manufacturers Association, which defines enclosures intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, and hose-directed water.
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| NEMA-7: A standard from the National Electrical Manufacturers Association, which defines explosion-proof enclosures for use in locations classified as Class I, Groups A, B, C or D, as specified in the National Electrical Code.
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| NEMA-Size Case: An older US case standard for panel meters, which requires a panel cutout of 3.93 x 1.69 inches.
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| Nernst Equation: A mathematical description of electrode behavior: E is the total potential, in millivolts, developed between the sensing and reference electrodes; Ex varies with the choice of electrodes, temperature, and pressure: 2.3RT/nF is the Nernst factor (R and F are constants, n is the charge on the ion, including sign, T is the temperature in degrees Kelvin), and ai is the activity of the ion to which the electrode is responding.
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| Nernst Factor (S, Slope): The term 2.3RT/nF is the Nernst equation, which is equal (at T = 25?C) to 59.16 mV when n = 1 and 29.58 mV when n - 2, and which includes the sign of the charge on the ion in the term n. The Nerst factor varies with temperature. |
| NETD (or NE?T) Noise Equivalent Temperature Difference or the change in temperature of a blackbody target that fills the radiometer FOV which results in a change in the radiometer signal equal to the rms noise of the instrument.
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| Netscape A WWW Browser and the name of a company. The Netscape (tm) browser was originally based on the Mosaic program developed at the National Center for Supercomputing Applications (NCSA). |
| Network: A group of computers that are connected to each other by communications lines to share information and resources. |
| Neutral Density Filter: An optical or infrared filter for which the transmission is constant and not a function or wavelength. |
| Neutrino: A lepton with no electric charge. Neutrinos participate only in weak and gravitational interactions and are therefore very difficult to detect. There are three known types of neutrinos, all of which are very light and could possibly have zero mass |
| Neutron (n): A baryon with electric charge zero; it is a fermion with a basic structure of two down quarks and one up quark (held together by gluons). The neutral component of an atomic nucleus is made from neutrons. Different isotopes of the same element are distinguished by having different numbers of neutrons in their nucleus. |
| Neutron: An elementary particle slightly heavier than a proton, with no electric charge.
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| Newton (N): A metric unit of force measurement equivalent to 0.2248 ... lb.
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| Newtons 1st and 2nd laws of motion: F = d(mv)/dt.
F is the net (total) force acting on the body of mass m. The individual forces acting on m must be summed vectorially. In the special case where the mass is constant, this becomes F = ma.
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| Newtons third law of motion: When body A exerts a force on body B, then B exerts and equal and opposite force on A. The two forces related by this law act on different bodies. The forces need not be net forces.
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| Nibble: One half of a byte.
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| NIC -- (Network Information Center) Generally, any office that handles information for a network. The most famous of these on the Internet was the InterNIC, which was where most new domain names were registered until that process was decentralized to a number of private companies. |
| NIC: Network Information Center. An organization which provides network users with information about services provided by the network.
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| Nicrosil/Nisil: A nickel chrome/nickel silicone thermal alloy used to measure high temperatures. Inconsistencies in thermoelectric voltages exist in these alloys with respect to the wire gage.
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| NIST: National Institute of Standards & Technology.
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| NMR (Normal-Mode Rejection): The ability of a panel meter to filter out noise superimposed on the signal and applied across the SIG HI to SIG LO input terminals. Normally expressed in dB at 50/60 Hz.
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| NNTP -- (Network News Transport Protocol The protocol used by clientand server software to carry USENET postings back and forth over a TCP/IP network. If you are using any of the more common software such as Netscape, Nuntius, Internet Explorer, etc. to participate in newsgroups then you are benefiting from an NNTP connection |
| Noble Metal: A metal with high resistance to chemical reaction, especially oxidation and solution by organic acids; sometimes called a precious metal.
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| Node: A terminal on a data communications network.
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| Noise Floor : (1) A cutoff point from which no appreciable information from a signal can be retrieved below. (2) The minimum discernible signal that can be detected by a receiver.
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| Noise: An unwanted electrical interference on the signal wires. |
| Nominal Ratio, Haskel Liquid Pumps The "actual Ratio" multiplied by a factor to account for losses due to internal friction in the pump. This number is normally used to determine the maximum attainable pressure where some flow can still occur. The friction factor normally used for pumping non-lubricating fluids is .88( 12% friction). For lubricated fluids, it will be lower percentage, and the stall pressure will be somewhat higher. |
| Nondestructive Testing: (NDT) a procedure for determining the quality or characteristics of a material, part, or assembly without permanently altering it or its properties; examples include ultrasonic and radiographic inspection.
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| Nonincendive: Nonincendive circuits are those which may spark under normal operating conditions, but which may not release enough energy to cause ignition. Circuits may contain enough energy for potential ignition should both the equipment fail and the process fail (two concurrent failures). |
| Normal (axial) Stress: The force per unit area on a given plane within a body a = F/A
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| Normal Hydrogen Electrode: A reversible hydrogen electrode (Pt) in contact with hydrogen gas at 1 atmosphere partial pressure and immersed in a solution containing hydrogen ions at unit activity.
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| Normal-mode Rejection Ratio: The ability of an instrument to reject interference usually of line frequency (50-60 Hz) across its input terminals.
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| Notch Brittleness: A measure of the susceptibility of a material to brittle fracture at locations of stress concentration. For example, in a notch tensile test a material is said to be notch brittle if its notch strength is less than its tensile strength; otherwise, it is said to be notch ductile.
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| NPSH Net Positive Suction Head, |
| NPT: National Pipe Thread.
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| NTSC standard : Abbreviation for National Television Standards Committee standard. The North American standard (525-line interlaced raster-scanned video) for the generation, transmission, and reception of television signals.
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| Nucleus: The nucleus of an atom is the central core that comprises almost all the weight of the atom. All atomic nuclei (except H-1, which has a single proton) contain both protons and neutrons.
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| Null: A condition, such as balance, which results in a minimum absolute value of output.
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| Nyquist Theorem: This theorem says that if a continuous bandwidth-limited signal contains no frequency components higher than fC then the original signal can be recovered without distortion if it is sampled at a rate of at least 2 fC. This theorem applies to A/D converter applications as well as data transmission density over limited-bandwidth channels. |
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