The Illustrated Dictionary of Electronics - Loscha

4 absolute units • A-B testabsolute units Fundamental physical units (seeABSOLUTE SYSTEM OF UNITS) from which allothers are derived. See, for example, AMPERE,OHM, VOLT, and WATT.absolute value The magnitude of a quantity withoutregard to sign or direction. The absolute valueof a is written |a|. The absolute value of a positivenumber is the number itself; thus, |10|equals 10. The absolute value of a negative numberis the number with its sign changed: |-10|equals 10.absolute-value circuit A circuit that produces aunipolar signal in response to a bipolar input andin proportion to the absolute value of the magnitudeof the input.absolute-value computer A computer in whichdata is processed in its absolute form; i.e., everyvariable maintains its full value. (Compare toINCREMENTAL COMPUTER.)absolute-value device In computer practice, a devicethat delivers a constant-polarity outputsignal equal in amplitude to that of the inputsignal. Thus, the output signal always has thesame sign.absolute zero The temperature –273.16°C(459.7°F and 0 Kelvin). The coldest possibletemperature, representing the complete absenceof heat energy.absorbed wave A radio wave that dissipates in theionosphere as a result of molecular agitation.This effect is most pronounced at low andmedium frequencies.absorptance The amount of radiant energy absorbedin a material; equal to 1 minus the transmittance.absorption The taking up of one material or mediumby another into itself, as by sucking orsoaking up. Also, the retention of one medium (ora part of it) by another medium, through whichthe first one attempts to pass. See, for example,ABSORBED WAVE, ABSORPTION COEFFI-CIENT, DIELECTRIC ABSORPTION. CompareADSORPTION.absorption band See ABSORPTION SPECTRUM.absorption circuit A circuit that absorbs energyfrom another circuit or from a signal source—especiallya resonant circuit, such as a wavemeteror wavetrap.absorption current In a capacitor, the current resultingfrom absorption of energy by the dielectricmaterial.absorption dynamometer A power-measuring instrumentin which a brake absorbs energy from arevolving shaft or wheel.absorption fading Fading of a radio wave, resultingfrom (usually) slow changes in the absorptionof the wave in the line of propagation.absorption frequency meter See WAVEMETER.absorption line See ABSORPTION SPECTRUM.absorption loss 1. Transmission loss caused bydissipation of electrical energy, or conversion of itinto heat or other forms of energy. 2. Loss of all orpart of a skywave because of absorption by theionosphere. Also called ionospheric absorption oratmospheric absorption.absorption marker A small blip introduced ontoan oscilloscope trace to indicate a frequencypoint. It is so called because it is produced by theaction of a frequency-calibrated tuned trap, similarto an absorption wavemeter.absorption modulation Amplitude modulation of atransmitter or oscillator by means of an audiofrequency-actuatedabsorber circuit. In its simplestform, the modulator consists of a few turns of wirecoupled to the transmitter tank coil and connectedto a carbon microphone. The arrangementabsorbs energy from the transmitter at a varyingrate as the microphone changes its resistance inaccordance with the sound waves it receives.absorption spectrum For electromagnetic waves, aplot of absorption coefficient (of the medium ofpropagation) versus frequency. Also called EMIS-SION SPECTRUM.absorption trap See WAVETRAP.absorption wavemeter A resonant-frequency indicatinginstrument that is inductively coupled tothe device under test.absorptivity In audio and microwave technologies,a measure of the energy absorbed by a given volumeof material.A-B test Comparison of two sounds by reproducingthem in alternating succession.