GLOSSARY
Select the first letter of the desired search item. We will then
display the matching terms that begin with that letter.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
g: The force of acceleration due to gravity equal to 32.1739 ft/sec2 or 386
in./sec2.
Gage Factor: A measure of the ratio of the relative change of resistance to the relative
change in length of a piezoresistive strain gage.
Gage Length: The distance between two points where the measurement of strain occurs.
Gage Pressure Transducer: A transducer which measures pressure in relation to the ambient
pressure.
Gage pressure: Absolute pressure minus local atmospheric pressure.
Gain: The amount of amplification used in an electrical circuit.
Galvanometer: An instrument that measures small electrical currents by means of deflecting
magnetic coils.
GPH: Volumetric flow rate in gallons per hour.
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.
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.
Half Bridge: Two active elements or strain gages.
Half-Duplex: One way at a time data communication; both devices can transmit and receive
data, but only one at a time.
Handshake: An interface procedure that is based on status/data signals that assure orderly
data transfer as opposed to asynchronous exchange.
Hardcopy: Output in a permanent form (usually a printout) rather than in temporary form, as
on disk or display terminal.
Hardware: The electrical, mechanical and electromechanical equipment and parts associated
with a computing system, as opposed to its firmware or software.
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.
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.
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 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: Thermal energy. Heat is expressed in units of calories or BTU's.
Hertz (Hz): Units in which frequency is expressed. Synonymous with cycles per second.
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.
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.
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).
Host: The primary or controlling computer in a multiple part system.
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+).
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 difference in output when the measurand value is first approached with
increasing and then with decreasing values. Expressed in percent of full scale during any one
calibration cycle. See also Deadband.
Icon: A graphic functional symbol display. A graphic representation of a
function or functions to be performed by the computer.
ICP: Integrated Circuit Piezoelectric; term sometimes used to describe an accelerometer
with built-in electronics.
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.
Initial Unbalance: Initial unbalance is that unbalance of any kind that exists in the rotor
before balancing.
Input Impedance: The resistance measured across the excitation terminals of a transducer.
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 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.
Insulated Junction: See Ungrounded Junction
Insulation Resistance: The resistance measured between two insulated points on a transducer
when a specific dc voltage is applied at room temperature.
Integral: A form of temperature control. See Automatic Reset, #2
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.
Interface: The means by which two systems or devices are connected and interact with each
other.
Internal Reference electrode (Element): The reference electrode placed internally in a
glass electrode.
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.
Interrupt: To stop a process in such a way that it can be resumed.
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.
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.
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.
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.
IPTS-68: International Practical Temperature Scale of 1968. Fixed points in thermometry set
by the 1968 General Conference of Weights and Measures.
ISA: Instrument Society of America.
Isolation: The reduction of the capacity of a system to respond to an external force by use
of resilient isolating materials.
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.
Isothermal: A process or area that is a constant temperature.
| 
)