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electromechanical • electromigration 243
electromechanical Descriptive of any device that
converts energy from electrical to mechanical
form or vice-versa. Examples are the motor and
the generator.
electromechanical amplifier An amplifier that
converts an electrical input signal into mechanical
motion (vibratory or rotary), which it then
converts back into an electrical output signal of
higher current, voltage, or power.
electromechanical chopper A vibrator-type interrupter
used primarily to chop direct current, converting
it into a square-wave signal, whose
amplitude is proportional to current strength.
Also see CHOPPER.
electromechanical counter A device that indicates
the number of pulses that have been applied
to it. Typically, it has a series of dials—each
capable of displaying the numerals 0 to 9 in sequence,
one for each decade in the count. The dials
are geared together, the train being operated
by the stepping action of an electromagnetic escapement.
Compare ELECTRONIC COUNTER.
electromechanical energy The energy stored by
an inductor or capacitor in an electromechanical
device.
electromechanical filter See ULTRASONIC FIL-
TER, 1.
electromechanical flip-flop See BISTABLE RELAY.
electromechanical frequency meter A usually direct-reading
instrument for measuring frequency
in the lower and middle portions of the audio
spectrum. It works via the mechanical motion resulting
from the applied signal. The two varieties
are the movable-iron type and the reed type.
electromechanical modulator See CHOPPER.
electromechanical oscillator An oscillator consisting
of an electromechanical amplifier provided
with regenerative feedback.
electromechanical oscilloscope A galvanometertype
instrument for displaying a varying or alternating
current or voltage. The signal is applied to
a meter movement having a movable coil, which
swings or vibrates in response to the signal. A
tiny mirror cemented to the coil reflects a beam of
light to a rotating mirror that sweeps the beam
across a translucent screen on which the image is
produced.
electromechanical recorder An instrument in
which a pen or stylus is moved on a sheet of paper
by the varying signal current or voltage being
recorded.
electromechanical rectifier A rectifier in which a
moving part, such as a vibrating reed or rotating
commutator-slip-ring unit, is driven by alternating
current (ac) to close the circuit during positive
or negative ac half-cycles, thus rectifying the ac.
Compare ELECTROLYTIC RECTIFIER and ELEC-
TRONIC RECTIFIER.
electromechanical relay An electromagnetic
switch consisting of a multiturn coil wound on an
iron core near an armature with a movable end
contact. When control current flows through the
coil, it becomes magnetized and attracts the armature,
closing the movable contact against a
stationary one.
Switched
terminals
Actuating
current
electromechanical relay
Movable contact
Fixed contact
Iron-core coil
(electromagnetic)
electromechanical timer A device for automatically
timing a process or an observed event. Most
such timers are based on an accurate clock (electric
or spring driven) that opens or closes
contacts at predetermined instants. Compare
ELECTRONIC TIMER.
electromechanical transducer A transducer that
translates mechanical signals directly into electrical
ones or vice versa, without the intermediary
of active devices, such as transistors or integrated
circuits.
electromechanical valve A usually poppet-type
valve for gases or liquids. The valve is operated by
electromagnetic action and is often aided by an
electronic (servo) circuit.
electromechanics The theory and application of
electromechanical devices.
electromedical engineering The branch of electronics
engineering concerned with the theory,
design, and application of electronic equipment
for medical diagnosis or treatment.
electromedical equipment Electrical or electronic
equipment used in medical diagnosis or treatment.
electromerism Ionization in gases.
electrometallurgy The branch of metallurgy concerned
with the use of electricity (especially in
electrolysis) to separate or purify metals or to furnish
heat for metallurgical processes.
electrometer A specially designed, highly sensitive
electronic voltmeter used to measure extremely
low voltages and, indirectly, extremely low currents.
It is sometimes used as a galvanometer.
electrometer amplifier A stable low-noise amplifier
for increasing the sensitivity of an electrometer.
electrometry The science of electrical measurements.
electromigration The movement of atoms in a
substance from one place to another, because of
interaction between electrons and ions in the
presence of electric currents. This effect can
cause the eventual deterioration of certain semiconductor
devices.