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

Hexadecimal
Refers to a base sixteen number system using the characters 0 through 9 and A through F to represent the values. Machine language programs are often written in hexadecimal notation.

Hertz (Hz)
Units in which frequency is expressed. Synonymous with cycles per second.

Heat Treating
A process for treating metals where heating to a specific temperature and cooling at a specific rate changes the properties of the metal.

Heat Transfer
The process of thermal energy flowing from a body of high energy to a body of low energy. Means of transfer are: conduction; the two bodies contact. Convection; a form of conduction where the two bodies in contact are of different phases, i.e. solid and gas. Radiation: all bodies emit infrared radiation.

Heat
Thermal energy. Heat is expressed in units of calories or BTU's.

Heat Sink
1. Thermodynamic. A body which can absorb thermal energy. 2. Practical. A finned piece of metal used to dissipate the heat of solid state components mounted on it.

Header
The portion of a packet, preceding the actual data, containing source and destination addresses and error-checking fields.

Head Loss
The loss of pressure in a flow system measured using a length parameter (i.e., inches of water, inches of mercury).

Head Pressure
Pressure in terms of the height of fluid, P = yrg, where r = fluid density and y = the fluid column heights. Expression of a pressure in terms of the height of fluid, r = yrg, where r is fluid density and y = the fluid column height. g = the acceleration of gravity.

HART
Highway Addressable Remote Transducer.

HDTV
High Definition Television.

Harmonic Distortion
A type of communications line interface that is caused by erroneous frequencies that are generated by non-linearities in the system.

Harmonic
A frequency that is a multiple of the fundamental. See also Distortion and Non-Linearity.

Hardware
The electrical, mechanical and electromechanical equipment and parts associated with a computing system, as opposed to its firmware or software.

Hardcopy
Output in a permanent form (usually a printout) rather than in temporary form, as on disk or display terminal.

Handshake
An interface procedure that is based on status/data signals that assure orderly data transfer as opposed to asynchronous exchange.

Half-Life
The time in which half the atoms of a radioactive substance will have disintegrated, leaving half the original amount. Half of the residue will disintegrate in another equal period of time.

Half-Duplex
One way at a time data communication; both devices can transmit and receive data, but only one at a time.

GUI
Graphical user interface.

Grounded Junction
A form of construction of a thermocouple probe where the hot or measuring junction is in electrical contact with the sheath material so that the sheath and thermocouple will have the same electrical potential.

GPM
Volumetric flow rate in gallons per minute.

Ground
1. The electrical neutral line having the same potential as the surrounding earth. 2. The negative side of DC power supply. 3. Reference point for an electrical system.

Gopher
A menu based system for exploring Internet resources.

GPH
Volumetric flow rate in gallons per hour.

Glithch
A spike caused by the skew of switches or logic. Glitches are a troublesome source of error in high-speed D/A convertors and they are most prevalent at the mid scale switching location.

General Communications Interface
An ISDN interchip standard interface for both basic rate and primary rate equipment.

GATT
General Agreement on Tariffs and Trade.

Galvanometer
An instrument that measures small electrical currents by means of deflecting magnetic coils.

Gateway
A special dedicated computer that attaches to two or more networks and routes packets from one network to the other.

Gain
The amount of amplification used in an electrical circuit. Gain is usually measured in decibels, but it can also be expressed as the ratio of output power to input power.

Gage Pressure Transducer
A transducer which measures pressure in relation to atmospheric pressure.

Gage Length
The distance between two points where the measurement of strain occurs.

Gage Factor
A measure of the ratio of the relative change of resistance to the relative change in length of a piezoresistive strain gage.

Functions
Three mode PID controller. A time proportioning controller with integral and derivative functions. The integral function automatically adjusts the system temperature to the set point temperature to eliminate droop due to the time proportioning function.

Full Scale
See Rated Capacity.

Full Scale Output
The algebraic difference between the minimum output (normally zero) and the rated capacity.

Full Bridge
A Wheatstone bridge configuration utilizing four active elements or strain gages.

Full Duplex
Communications that takes place in both directions at the same time.

FTP
File Transfer Protocol. The Internet standard high-level protocol for transferring files from one computer to another.

Frequency, Natural
The frequency of free (not forced) oscillations of the sensing element of a fully assembled transducer.

Frequency Response
The range of frequencies over which the transducer voltage output will follow the sinusoidally varying mechanical input within specified limits.

Frequency
The number of cycles over a specified time period over which an event occurs. The reciprocal is called the period.

Frequency Output
An output in the form of frequency which varies as a function of the applied input.

Frame
A sequence of time slots in ISDN. A basic rate interface frame consists of 48 time slots repeated every 250 microseconds.

Freezing Point
The temperature at which the substance goes from the liquid phase to the solid phase.

FPS
Flow velocity in feet per second.

Forced Vibration
Vibration of a system caused by an imposed force. Steady-state vibration is an unchanging condition of periodic or random motion.

FPM
Flow velocity in feet per minute.

FM Approved
An instrument that meets a specific set of specifications established by Factory Mutual Research Corporation.

FM
Factory Mutual Research Corporation. An organization which sets industrial safety standards.

Flush Diaphragm
Sensing element is located on the very tip of the transducer (NO pressure port).

Flow Rate
Actual speed or velocity of fluid movement .

Flowmeter
A device used for measuring the flow or quantity of a moving fluid.

Flow
Travel of liquids or gases in response to a force (i.e. pressure or gravity).

Floppy Disk
A small, flexible disk carrying a magnetic medium in which digital data is stored for later retrieval and use.

Flag
Any of various types of indicators used for identification of a condition or event; for example, a character that signals the termination of a transmission.

Firmware
Software instructions stored in ROMs.

Filter
An electrical circuit that passes frequencies within a specified frequency band and attenuates signals that fall outside of that frequency band.

Filling Solution
A solution of defined composition to make contact between an internal element and a membrane or sample. The solution sealed inside a pH glass bulb is called an internal filling solution. This solution normally contains a buffered chloride solution to provide a stable potential and a designated zero potential point. The solution which surrounds the …

File
A set of related records or data treated as a unit.

FIFO Memory
A type of memory with separate input and output ports. The first data to enter the input port are the first to exit the output port.

Field of View
A volume in space defined by an angular cone extending from the focal plane of an instrument.

Fiber Optics
A transmission medium consisting of thin strands of glass or plastic through which data is sent by means of pulse modulated light waves.

FFT
Fast Fourier Transform. A computationally efficient mathematical technique which converts digital information from the time domain to the frequency domain for rapid spectral analysis.

Ferrule
A compressible tubular fitting that is compressed onto a probe inside a compression fitting to form a gas-tight seal.

Exposed Junction
A form of construction of a thermocouple probe where the hot or measuring junction protrudes beyond the sheath material so as to be fully exposed to the medium being measured. This form of construction usually gives the fastest response time.

Explosion-proof Enclosure
An enclosure that can withstand an explosion of gases within it and prevent the explosion of gases surrounding it due to sparks, flashes or the explosion of the container itself, and maintain an external temperature which will not ignite the surrounding gases.

Expansion Factor
Correction factor for the change in density between two pressure measurement areas in a constricted flow.

Exothermic
Gives off heat. A process is said to be exothermic when it releases heat.

Excitation
The external application of electrical voltage current applied to a transducer for normal operation.

Eutectic Temperature
The lowest possible melting point of a mixture of alloys.

Ethernet
A LAN standard, also known as IEE 802.3, that connects computers by means of coaxial cable or twisted paid conductors.

Error Band
The allowable deviations to output from a specific reference norm. Usually expressed as a percentage of full scale.

Error
The difference between the value indicated by the transducer and the true value of the measurand being sensed. Usually expressed in percent of full scale output.

Equivalent Conductance (l)
Equivalent conductance of an electrolyte is defined as the conductance of a volume of solution containing one equivalent weight of dissolved substances when placed between two parallel electrodes 1 cm apart, and large enough to contain between them all of the solution. l is never determined directly, but is calculated from the specific conductance …

Equilibrium Constant
The product of the concentrations (or activities) of the substances produced at equilibrium in a chemical reaction divided by the product of concentrations of the reacting substances, each concentration raised to that power which is the coefficient of the substance in the chemical equation.

Equalization
Compensation for frequency dependent attenuation in a comunications circuit.

Eprom
Erasable Programmable Read-Only Memory. The PROM can be erased by ultraviolet light or electricity.

Environmental Conditions
All conditions in which a transducer may be exposed during shipping, storage, handling, and operation.

Endothermic
Absorbs heat. A process is said to be endothermic when it absorbs heat.

Enthalpy
The sum of the internal energy of a body and the product of its volume multiplied by the pressure.

End Points
The end points of a full scale calibration curve.

Encryption
A technique of modifying a bit stream to make it appear to be a random sequence of bits to someone who does not have access to the encryption scheme.

End Point (Potentiometric)
The apparent equivalence point of a titration at which a relatively large potential change is observed.

Encoding
The process of putting information into digital format.

EMI
Electromagnetic Interference (Emission).

Emissivity
The ratio of energy emitted by an object to the energy emitted by a blackbody at the same temperature. The emissivity of an object depends upon its material and surface texture; a polished metal surface can have an emissivity around 0.2 and a piece of wood can have an emissivity around 0.95.

EMF
Electromotive force. A rise in (electrical) potential energy. The principal unit is the volt.

Electrolyte
Any substance which, when in solution will conduct an electric current. Acids, bases, and salts are common electrolytes.

Electromotive Force (emf)
The potential difference between the two electrodes in a cell. The cell emf is the cell voltage measured when no current is flowing through the cell. It can be measured by means of a pH meter with high input impedance.

Electrode Potential (E)
The difference in potential established between an electrode and a solution when the electrode is immersed in the solution.

EEPROM
Electrically Eraseable Programmable Read Only Memory.

Electrical Interference
Electrical noise induced upon the signal wires that obscures the wanted information signal.

Dynamic Range
The ratio of the maximum output signal to the smallest output signal that can be processed in a system, usually expressed logarithmically in dB. Dynamic range can be specified in terms of harmonic distortion, signal to noise ration, or other performance criteria.

Dynamic Pressure
The difference in pressure levels from static pressure to stagnation pressure caused by an increase in velocity. Dynamic pressure increases by the square of the velocity.

Dynamic Calibration
Calibration in which the input varies over a specific length of time and the output is recorded vs. time.

Duplex Wire
A pair of wires insulated from each other and with an outer jacket of insulation around the inner insulated pair.

Duty Cycle
The total time to one on/off cycle. Usually refers to the on/off cycle time of a temperature controller.

Duplex
Pertaining to simultaneous two-way independent data communication transmission in both direction. Same as 'full duplex'.

Dual-slope A-D Converter
An analog-to-digital converter which integrates the signal for a specific time, then counts time intervals for a reference voltage to bring the integrated signal back to zero. Such converters provide high resolution at low cost, excellent normal-mode noise rejection, and minimal dependence on circuit elements.