Page 18 - The Illustrated Dictionary of Electronics

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absolute error • absolute tolerance 3

value. This difference is positive when the ap-
proximate value is higher than the exact value,
and it is negative when the approximate value is
lower than the exact value. Compare RELATIVE
ERROR.
absolute gain Antenna gain for a given orientation
when the reference antenna is isolated in space
and has no main axis of propagation.
absolute humidity The mass of water vapor per
unit volume of air. Compare RELATIVE HUMID-
ITY.
absolute instruction A computer instruction that absolute Peltier coefficient The product of the
states explicitly and causes the execution of a absolute Seebeck coefficient and absolute tem-
specific operation. perature of a material.
absolute magnitude For a complex number quan- absolute pitch A tone in a standard scale, deter-
tity, the vector sum of the real and imaginary mined according to the rate of vibration, indepen-
components (i.e., the square root of the sum of dent of other tones in the range of pitch.
the squares of those components). Also see AB- absolute pressure Pressure (force per unit area) of
SOLUTE VALUE and IMPEDANCE. a gas or liquid determined with respect to that of
absolute maximum rating The highest value a a vacuum (taken as zero).
quantity can have before malfunction or damage absolute-pressure transducer A transducer actu-
occurs. ated by pressure from the outputs of two different
absolute maximum supply voltage The highest pressure sources, and whose own output is pro-
supply voltage that can be applied to a circuit portional to the difference between the two ap-
without permanently altering its characteristics. plied pressures.
absolute measurement of current Measurement absolute scale 1. A scale in which the zero value
of a current directly in terms of defining quan- indicates the lowest physically possible value that
tities. 1. TANGENT GALVANOMETER method: a parameter can attain. 2. A standard scale
Current is proportional to the tangent of the an- for measurement of a quantity. 3. A universally
gle of deflection of the needle of this instrument. agreed-upon scale for the determination of a vari-
Deflection depends on torque, resulting from the able quantity. 4. The Kelvin temperature scale.
magnetic field produced by current in the gal- 5. The Rankine temperature scale.
vanometer coil acting against the horizontal absolute Seebeck coefficient The quotient, as an
component of the earth’s magnetic field. integral from absolute zero to the given tempera-
2. ELECTRODYNAMOMETER method: With this ture, of the Thomson coefficient of a material di-
2-coil instrument, current is determined from vided by its absolute temperature.
the observed deflection, the torque of the sus- absolute spectral response The frequency output
pension fiber of the movable coil, and the coil di- or response of a device in absolute power units
mensions. (such as milliwatts) as opposed to relative units
absolute measurement of voltage Measurement (such as decibels).
of a voltage directly in terms of defining quan- absolute system of units A system of units in
tities. 1. CALORIMETRIC method: A current- which the fundamental (ABSOLUTE) units are
carrying coil immersed in water raises the those expressing length (l), mass (m), charge (q),
temperature of the water. The difference of and time (t). All other physical units, including
potential that forces the current through the coil practical ones, are then derived from these abso-
then is determined in terms of the equivalent heat lute units.
energy. 2. Disk-electrometer method: In this absolute temperature Temperature measured on
setup, a metal disk attached to one end of a either the Kelvin or Rankine scales, where zero
balance beam is attracted by a stationary disk represents the total absence of heat energy.
mounted below it, the voltage being applied to the absolute temperature scale 1. The Kelvin temper-
two disks. The other end of the beam carries a ature scale, in which the divisions are equal in
pan into which accurate weights are placed. At size to 1° Celsius, and the zero point is absolute
balance, the voltage is determined in terms of the zero, the coldest possible temperature, approxi-
weight required to restore balance, the upper-disk mately –273.16° Celsius. 2. The Rankine temper-
area, and the disk separation. ature scale, in which the divisions are equal in
absolute minimum resistance The resistance be- size to 1° Fahrenheit, and the zero point is abso-
tween the wiper and the nearer terminal of a po- lute zero or approximately –459.7° Fahrenheit.
tentiometer, when the wiper is as close to that absolute tolerance The value of a component as it
terminal as physically possible. All potentiome- deviates from the specified or nominal value. It is
ters have two such specifications, one for each usually expressed as a percentage of the specified
end terminal. value.