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Flowmeter directory - Flow controllers terms Category: Electronics and Engineering > Industrial automation Date & country: 16/12/2007, UK Words: 713

Mounting Error
The error resultant from installing the transducer, both electrical and mechanical.

Mounted Resonant Frequency
The frequency at which the internal spring/mass system of an accelerometer resonates, producing a 90 degree phase shift in output signal vs. applied acceleration.

Motherboard
The pc board of a computer that contains the bus lines and edge connectors to accommodate other boards in the system. In a microcomputer, the motherboard contains the microprocessor and connectors for expansion boards.

Molality
A measure of concentration expressed in mols per kilogram of solvent.

Monovalent Ion
An ion with a single positive or negative charge (H+, C1-).

Modulation
The process by which some characteristic of a higher frequency wave is varied in accordance with the amplitude of a lower frequency wave.

Modem
Modulator/Demodulator. A device that transforms digital signals into audio tones for transmission over telephone lines, and does the reverse for reception.

MIPS
Million Instructions Per Second.

Mineral-insulated Thermocouple
A type of thermocouple cable which has an outer metal sheath and mineral (magnesium oxide) insulation inside separating a pair of thermocouple wires from themselves and from the outer sheath. This cable is usually drawn down to compact the mineral insulation and is available in diameters from .375 to .010 inches. It is ideally suited for high-tempe…

Millimeter
One thousandth of a meter, symbol mm.

Millivolt
Unit of electromotive force. It is the difference in potential required to make a current of 1 millampere flow through a resistance of 1 ohm; one thousandth of a volt, symbol mV.

Milliamp
One thousandth of an amp, 10-3 amps, symbol mA.

Microvolt
One millionth of a volt, 10-6 volts.

Mil
One thousandth of an inch (.001').

Microamp
One millionth of an ampere, 10-6 amps, µA.

Micron
One millionth of a meter, 10-6 meters.

Mica
A transparent mineral used as window material in high-temperature ovens.

MFLOPS
Million Floating Point Instructions Per Second.

Method of Correction
A procedure whereby the mass distribution of a rotor is adjusted to reduce unbalance, or vibration due to unbalance, to an acceptable value. Corrections are usually made by adding material to, or removing it from, the rotor.

Membrane
The pH-sensitive glass bulb is the membrane across which the potential difference due to the formation of double layers with ion-exchange properties on the two swollen glass surfaces is developed. The membrane makes contact with and separates the internal element and filling solution from the sample solution.

Melting Point
The temperature at which a substance transforms from a solid phase to a liquid phase.

Measuring Junction
The thermocouple junction referred to as the hot junction that is used to measure an unknown temperature.

Mechanical Hysteresis
The difference of the indication with increasing and decreasing strain loading, at identical strain values of the specimen.

Measurand
A physical quantity, property, or condition which is measured.

Measured Media
The physical quantity, property, or condition which is measured. (eg: pressure, load, weight, acceleration)

Mean Temperature
The average of the maximum and minimum temperature of a process equilibrium.

Maximum Operating Temperature
The maximum temperature at which an instrument or sensor can be safely operated.

Maximum Excitation
The maximum value of excitation voltage or current that can be applied to the transducer at room conditions without causing damage or performance degradation beyond specified tolerances.

Mass Flow Rate
Volumetric flowrate times density, i.e. pounds per hour or kilograms per minute.

Mass Storage
A device like a disk or magtape that can store large amounts of data readily accessible to the central processing unit.

Manual Reset (Switch)
The switch in a limit controller that manually resets the controller after the limit has been exceeded.

LVDT
This has been taken from a paper prepared at University of Ca. in Berkeley. Good Overview of operation.

LVDT
Very brief overview from Univ of Colorado.

LSD (Least-Significant Digit)
The rightmost active (non-dummy) digit of the display.

LS-TTL Unit Load
A load with LS-TTL voltage levels, which will draw 20 µA for a logic 1 and -400 µA for a logic 0.

LS-TTL Compatible
For digital input circuits, a logic 1 is obtained for inputs of 2.0 to 5.5 V which can source 20 µA, and a logic 0 is obtained for inputs of 0 to 0.8 V which can sink 400 µA. For digital output signals, a logic 1 is represented by 2.4 to 5.5 V with a current source capability of at least 400 µA; and a logic 0 is represented by 0 to 0.6 V with a cur…

Loopback
Directing signals back toward the transmitting terminal at some point along the communications path. Used as a method of troubleshooting.

Loop Resistance
The total resistance of a thermocouple circuit caused by the resistance of the thermocouple wire. Usually used in reference to analog pyrometers which have typical loop resistance requirements of 10 ohms.

Logarithmic Scale
A method of displaying data (in powers of ten) to yield maximum range while keeping resolution at the low end of the scale.

Load Buttons
The spherical like shape of the top surface of a load cell where the load is applied.

Load Impedance
The impedance presented to the output terminals of a transducer by the associated external circuitry.

LISP
List Processing Language.

Linearity
The maximum deviation of the calibration curve from a straight line between zero and full scale, expressed as a percent of full scale output and measured on increasing measured only.

Line Protocol
A control program used to perform data communication functions over network lines which consists of handshaking and line-control functions that move the data between the transmit and receive terminals.

Line Pressure
The maximum pressure in the pressure vessel or pipe for differential pressure measurement.

Limits of Error
A tolerance band for the thermal electric response of thermocouple wire expressed in degrees or percentage defined by ANSI specification MC-96.1 (1975).

Life Cycle
The minimum number of pressure cycles the transducer can endure and still remain within a specified tolerance.

Least-squares Line
The straight line for which the sum of the squares of the residuals (deviations) is minimized.

Leakage Rate
The maximum rate at which a fluid is permitted or determined to leak through a seal. The type of fluid, the differential Limits of Error: A tolerance band for the thermal electric response of thermocouple wire expressed in degrees or percentage defined by ANSI specification MC-96.1 (1975).

LAP
Link Access Protocol.

Latent Heat
Expressed in BTU per pound. The amount of heat needed (absorbed) to convert a pound of boiling water to a pound of steam.

LAN
Local Area Network. A network that takes advantage of the proximity of computers to offer relatively efficient, higher-speed communications than long-haul or wide-area networks.

Laminar Flow
Streamlined flow of a fluid where viscous forces are more significant than inertial forces, generally below a Reynolds number of 2000.

KVA
Kilovolt amperes (1000-volt amps).

Kinetic Energy
Energy associated with mass in motion, i.e., 1/2 rV2 where r is the density of the moving mass and V is its velocity.

Kilowatt (kw)
Equivalent to 1000 watts.

Kilowatt Hour (kwh)
1000 watthours. Kilovolt amperes (kva): 1000 volt amps.

Isothermal
A process or area that is a constant temperature.

Junction
The point in a thermocouple where the two dissimilar metals are joined.

Isopotential Point
A potential which is not affected by temperature changes. It is the pH value at which dE/dt for a given electrode pair is zero. Normally, for a glass electrode and SCE reference, this potential is obtained approximately when immersed in pH 7 buffer.

Isolation
The reduction of the capacity of a system to respond to an external force by use of resilient isolating materials.

ISO
International Standards Organization.

ISA
Industry Standard Architecture (PC-AT Bus) or Instrument Society of America.

IPTS-68
International Practical Temperature Scale of 1968. Fixed points in thermometry set by the 1968 General Conference of Weights and Measures.

IPTS-48
International Practical Temperature Scale of 1948. Fixed points in thermometry as specified by the Ninth General Conference of Weights and Measures which was held in 1948.

Ionic Strength
The weight concentration of ions in solution, computed by multiplying the concentration of each ion in solution (C) by the corresponding square of the charge on the ion (Z) summing this product for all ions in solution and dividing by 2:ionic strength - 1/2 _ Z2 C.

Ionic Mobility
Defined similarly to the mobility of nonelectrolytic particles, viz., as the speed that the ion obtains in a given solvent when influenced by unit power.

IOBASE-T Ethernet
A version of Ethernet that operates over twisted-pair wire at a speed of 10 Mb/s. IOBASE-T networks with more than two terminals must use an Ethernet hub and a star topology.

Intrinsically Safe
An instrument which will not produce any spark or thermal effects under normal or abnormal conditions that will ignite a specified gas mixture.

Interrupt
To stop a process in such a way that it can be resumed.

Interpreter
A system program that converts and executes each instruction of a high-level language program into machine code as it runs, before going onto the next instruction.

Internet Protocol (IP)
The network layer protocol for the Internet. It is the datagram protocol defined by RFC 791.

Internet Address
An assigned number which identifies a host in an Internet. It has two or three parts: network number, optional subnet number, and host number.

Internet
The global collection of interconnected regional and wide-area networks which use IP as the network layer protocol.

Interface
The means by which two systems or devices are connected and interact with each other.

Interchangeability Error
A measurement error that can occur if two or more probes are used to make the same measurement. It is caused by a slight variation in characteristics of different probes.

Integral Nonlinearity
This term describes the absolute accuracy of a converter. It is the maximum deviation, at any point in the transfer function, of the converter's output from its ideal value.

Insulation (Isolation) Resistance
The DC resistance expressed in ohms measured between any electrical connector pin or lead wire and the transducer body or case. Normally measured at 50 VDC.

Insulated Junction
See Ungrounded Junction

Input Resistance (Impedance)
The input resistance of a pH meter is the resistance between the glass electrode terminal and the reference electrode terminal. The potential of a pH-measuring electrode chain is always subject to a voltage division between the total electrode resistance and the input resistance.

Input Impedance
The resistance of a panel meter as seen from the source. In the case of a voltmeter, this resistance has to be taken into account when the source impedance is high; in the case of an ammeter, when the source impedance is low.

Input Impedance
The resistance measured across the excitation terminals of a transducer at room temperature, with no load applied, and with the output terminals open-circuited.

Initial Unbalance
Initial unbalance is that unbalance of any kind that exists in the rotor before balancing.

Impedance
The total opposition to electrical flow (resistive plus reactive).

Infrared
An area in the electromagnetic spectrum extending beyond red light from 760 nanometers to 1000 microns (106 nm). It is the form of radiation used for making non-contact temperature measurements.

ICP
Integrated Circuit Piezoelectric; term sometimes used to describe an accelerometer with built-in electronics.

Hysteresis (Electrode Memory)
When an electrode system is returned to a solution, equilibrium is usually not immediate. This phenomenon is often observed in electrodes that have been exposed to the other influences such as temperature, light, or polarization.

Hysteresis
The maximum difference between output readings for the same measured point, one point obtained while increasing from zero and the other while decreasing from full scale. The points are taken on the same continuous cycle. The deviation is expressed as a percent of full scale.

Hygrometer
Any instrument for measuring humidity.

Hygrometry
The subject of humidity measurement.

Hygroscopic
Tending to absorb water vapor.

Hydrogen Ion Activity (aH+)
Activity of the hydrogen ion in solution. Related to hydrogen ion concentration (CH+) by the activity coefficient for hydrogen (f H+).

Humidity
The presence of water vapor in air or other gases Some people use 'humidity' to mean relative humidity only. Strictly speaking, 'humidity' also refers to all kinds of absolute indications of humidity. For very low humidities, other more specific terms tend to be used .

Hub
A central node in a star network to which all other nodes are connected by means of point-to-point communications links.

Host Number
The part of an Internet address that designates which node on the (sub network is being addressed.

Host
The primary or controlling computer in a multiple part system.

Hooke's Law
Defines the basis for the measurement of mechanical stresses via the strain measurement. The gradient of Hooke's line is defined by the ratio of which is equivalent to the Modulus of Elasticity E (Young's Modulus).

Hold
Meter HOLD is an external input which is used to stop the A/D process and freeze the display. BCD HOLD is an external input used to freeze the BCD output while allowing the A/D process to continue operation.

Hit
For Internet sites, this is the common term for the numbers of times a site (or page) is accessed.

HEU
Highly Enriched Uranium.