Guiang, Rosabel N.

July 05, 2017

CEIT-05-902E MH 3:30-4:30P
Engr. Odilon B. Yangco

Analog - Information represented as continuously varying voltage or current rather than in

discrete levels as opposed to digital data varying between two discrete levels.
Amplitude modulation - The encoding of a carrier wave by variation of its amplitude in
accordance with an input signal. Abbreviation = AM
AMMETER - An instrument for measuring the flow of electrical current in amperes. Ammeters
are always connected in series with the circuit to be tested.
ANALOG IC - lntegrated circuits composed to produce, amplify, or respond to variable
voltages. They include many kinds of amplifiers that involve analog - to - digital conversions and
vice versa, timers, and inverters. They are known as Operational Amplifier Circuits or OP -
Amps.

A – Ampere
Active component - A component that changes the amplitude of a signal between output and
input.
Active filter - A filter that uses an amplifier as well as reactive components to pass or reject
selected frequencies.
Active region - The region of BJT (bipolar junction transistor) operation between saturation and
cutoff used for linear amplification.
Admittance - Measure (in Siemens) of how easily AC will flow through a circuit. Admittance is
the reciprocal of impedance. Symbol = Y.
Alkaline cell - Also known as an "alkaline manganese cell", a primary cell that delivers more
current than a carbon-zinc cell.
Alligator clip - Spring clip on the end of a test lead for making temporary connections.
Alternating current - An electric current that rises to a maximum in one direction, falls back to
zero and then rises to a maximum in the opposite direction and then repeats. Abbreviation = AC.
Alternator - another name for an AC generator (device used to transform mechanical energy
into AC electrical power).
Ammeter - A meter used to measure current.
Ampere - a unit of electrical current, also referred to as amp.
Amplifier - A circuit that increases the voltage, current, or power of a signal.
Amplitude - Magnitude or size of a signal voltage or current.
Anode - A positively charged electrode, as of an electrolytic cell, storage battery, or electron
tube.
Apparent power - Power attained in an AC circuit as a product of effective voltage and current
which reach their peak at different times.
AC coupling - Circuit that passes an AC signal while blocking a DC voltage.
AC/DC - Equipment that will operate from an AC or DC power source.
AC generator - Device that transforms mechanical energy into AC electrical power.
AC load line - A graph representing all possible combinations of AC output voltage and current
for an amplifier.
AC power supply - Power supply that delivers AC voltage.
ACTUATOR SOLENOID - The solenoid in the actuator housing on the back of the injection
pump which moves the control rack as commanded by the engine controller.
ALTERNATOR - A device which converts mechanical energy into electrical energy.
ALTERNATING CURRENT (AC) - A flow of electrons which reverses its direction of flow at
regular intervals in a conductor.
AMBIENT TEMPERATURE - The temperature of the surrounding medium, such as gas, air
or liquid, which comes into contact with a particular component.
AMPERE - A unit of measure for the flow of current in a circuit. One ampere is the amount of
current flow provided when one volt of electrical pressure is applied against one ohm of
resistance. The ampere is used to measure electricity much as "gallons per minute" is used to
measure water flow.
AMPERE-HOUR - A unit of measure for battery capacity. It is obtained by multiplying the
current (in amperes) by the time (in hours) during which current flows. For example, a battery
which provides 5 amperes for 20 hours is said to deliver 100 ampere - hours.
AMPLIFIER - A device of electronic components used to increase power, voltage, or current of
a signal.
AMPLITUDE - A term used to describe the maximum value of a pulse or wave. It is the crest
value measured from zero.
ANALOG GAUGE - A display device utilizing a varying current to cause a mechanical change
in the position of its needle.
ARMATURE - The movable part of a generator or motor. It is made up of conductors which
rotate through a magnetic field to provide voltage or force by electromagnetic induction. The
pivoted points in generator regulators are also called armatures.
ARTIFICIAL MAGNETS - A magnet which has been magnetized by artificial means. It is also
called, according to shape, a bar magnet or a horseshoe magnet.
ATOM - A particle which is the smallest unit of a chemical element. It is made up mainly of
electrons (minus charges) in orbit around protons (positive charges).
AUXiliARY SPEED SENSOR - The engine speed sensor located on the engine timing gear
cover. It serves as a back - up to the primary engine speed sensor.
AC
Alternating current. Consists of a periodic oscillation between two different voltages. Usually
said to look like a sine wave, but is not always.
AM
Amplitude modulation. In radio communications, a signal controls the amplitude of a carrier
wave that is at a much higher, constant frequency. The carrier wave is filtered out and a
loudspeaker plays based on the amplitude of the signal.
Ampere (A)
The SI unit for current I. (Commonly spoken as "amps", "milliamps", etc.) The ampere is
officially defined as that constant current which, if maintained in two straight parallel conductors
of infinite length, of negligible circular cross-section, and placed one meter apart in vacuum,
would produce between these conductors a force equal to 2×10-7 newton per meter of length.
There is another definition which is based on the deposition rate of silver (in electrolysis?),
which is much easier to measure. The other electronics units are derived units based on the
ampere definition.
Amplify
To increase the strength of the signal. Often an "amplifier" is used to pass a signal with both an
increase or a decrease in gain.
Anode
An electron collector. Means up the path from a negative to a positive voltage. An anode has a
more positive voltage relative to a cathode.
Attenuate
Decrease the strength of a signal.

Balanced bridge - Condition that occurs when a bridge circuit is adjusted to produce a zero
output. (Back to top)

Band-pass filter - A tuned circuit designed to pass a band of frequencies between a lower cut-
off frequency (f1) and a higher cut-off frequency (f2). Frequencies above and below the pass
band are heavily attenuated.

Band-stop filter - A tuned circuit designed to stop frequencies between a lower cut-off
frequency (f1) and a higher cut-off frequency (f2) of the amplifier while passing all other
frequencies.

Bandwidth - The numerical difference between upper and lower frequencies of a band of
electromagnetic radiation. Abbreviation = BW

Base - The region that lies between the emitter and collector of a bipolar junction transistor
(BJT).

Battery - A DC voltage source containing two or more cells that convert chemical energy to
electrical energy.

Baud - A unit of signaling speed equal to the number of signal events per second. Not
necessarily the same as bits per second.

Bias - A DC voltage applied to a device to control its operation.

Binary - A number system having only two symbols, 0 and 1. A base 2 number system.

Bipolar junction transistor - (BJT), A three terminal device in which emitter to collector
current is controlled by base current.

Bits per second - A measure of data speed for the number of bits transmitted or received each
second.

Breakdown voltage - Voltage at which the breakdown of a dielectric or insulator occurs.

Breakover voltage - Minimum voltage required to cause a DIAC to break down and conduct.

Bridge rectifier - A circuit using four diodes to provide full wave rectification. Converts an AC
voltage to a pulsating DC voltage.

Buffer - An amplifier used to isolate a load from a source.

BW - See Bandwidth.

Byte - Group of eight binary digits or bits.

Band-Pass Filter
An analog filter that absorbs low and high frequencies (f) but allows a band of frequencies in the
middle to pass through.
BJT
Bi-polar junction transistor. A transistor in which the resistance of the channel is controlled by a
current at the gate. Can be thought of as a current-controlled resistor. FET is the other major type
of transistor.

CALIBRATION - The determination or rectification of the graduations used on a testing

instrument.
CAPACITOR - A device which stores electrical energy. Commonly used for filtering out
voltage spikes.
CHARGE - To restore the active materials in a storage battery by the passage of direct current
through the battery cells in a direction opposite that of the discharging current.
CURRENT - Movement of electricity along a conductor. Current is measured in amperes.
CURRENT FLOW - The flow or movement of electrons from atom to atom in a conductor.
CYCLE - The change in an alternating electrical sine wave from zero to a positive peak to zero
to a negative peak and back to zero.
CYCLING - The process by which a battery is discharged and recharged.

Cable - Group of two or more insulated wires.

CAD - Abbreviation for "computer aided designs"

Calibration - To adjust the correct value of a reading by comparison to a standard.

Capacitance - The ability of a capacitor to store an electrical charge. The basic unit is a Farad.

Capacitor - An electronic component having capacitive reactance.

Carbon-film resistor - Device made by depositing a thin carbon film on a ceramic form.

Carbon microphone - Microphone whose operation depends on pressure variation in carbon

granules causing a change in resistance.
Carbon resistor - Resistor of fixed value made by mixing carbon granules with a binder which
is molded and then baked.

Cathode - A negatively charged electrode, as of an electrolytic cell, a storage battery, or an

electron tube.

Center tap - Midway connection between the two ends of a winding.

Center tapped rectifier - A circuit that make use of a center tapped transformer and two diodes
to provide full wave rectification.

Center tapped transformer - A transformer with a connection at the electrical center of a

winding.

Ceramic capacitor - Capacitor in which the dielectric is ceramic.

Charge - Quantity of electrical energy.

Charge current - Current that flows to charge a capacitor or battery when voltage is applied.

Chassis - Metal box or frame to mount components.

Chassis ground - Connection to a chassis.

Choke - Inductor used to oppose the flow of alternating current.

Circuit - Interconnection of components to provide an electrical path between two or more

components.

Circuit breaker - A protective device used to open a circuit when current exceeds a maximum
value. In effect a reusable fuse.

Clock - A square waveform used for synchronizing and timing of several circuits.

Closed circuit - Circuit having a complete path for current flow.

Coaxial cable - Transmission line in which the signal carrying conductor is covered by a
dielectric and another conductor.

Collector - The semiconductor region in a bipolar junction transistor (BJT) through which a flow
of charge carriers leaves the base region.

Color code - Set of colors used to indicate value of a component.

Common-anode display - A multi-segment light emitting diode (LED) with a single positive
voltage input connection. Separate cathode connections are provided for each individual
segment.

Common cathode display - A multi-segment light emitting diode (LED) with a single negative
voltage input connection. Separate anode connections are provided for each individual segment.

Comparator - An op-amp circuit that compares two inputs and provides a DC output indicating
the polarity relationship between the inputs.

Computer aide design - Software used to create 2D or 3D computer models.

Constant current circuit - Circuit used to maintain constant current to a load having resistance
that changes.

Contact - Current carrying part of a switch, relay or connector.

Continuity - Occurs when a complete path for current exists.

Conventional current flow - Concept of current produced by the movement of positive charges
towards the negative terminal of a source.

Copper loss - Power lost in transformers, generators, connecting wires and other parts of a
circuit due to current flow through the resistance of copper conductors.

Coupling - To electronically connect two circuits so that signal will pass from one to the other.

Crowbar - Circuit used to protect the output of a source from a short circuited load. Load
current is limited to a value the source can deliver without damage.

Crystal - Natural or synthetic piezoelectric or semiconductor material with atoms arranged with
some degree of geometric regularity.

Crystal-controlled oscillator - Oscillator that uses a quartz crystal in its feedback path to
maintain a stable output frequency.

Current - Measured in amps, it is the flow of electrons through a conductor. Also know as
electron flow.

Cutoff - Condition when an active device is biased such that output current is near zero or
beyond zero.

Cycle - When a repeating wave rises from zero to a positive maximum then back to zero and on
to a negative maximum and back to zero it is said to have completed one cycle.
Capacitor
An electronics component that stores energy in the form of electric charge (static electricity). It
resists a sudden change in voltage.
Cathode
An electron emitter. A cathode has a more negative voltage relative to some other place.
Choke
Another name for an inductor, specifically referring to those used in power regulation.
CMOS
Complementary metal oxide semiconductor. Complementary means that it has N-channel and P-
channel transistors. Metal oxide is the type of gate. CMOS is a type of Integrated Circuit (IC)
that is voltage based, since it is made of FETs. Digital circuits tend to use very little current,
because the paths for current flow are effectively open or closed circuits except during the
transition between states.
Coil
A helix of wire (the same shape as a spring or Slinky). Its height, width, thickness, and material
can all vary. Used as an inductor. The loops of wire can overlap.
Condenser
Another name for capacitor.
Conductance
The inverse of resistance. Measured in siemens (obsolete name mhos), which are the inverse of
ohms. 1 S = 1/Ω = 1 A/V = 1 A2/W
Coulomb (C)
The SI unit for electric charge Q. Defined in terms of the ampere. 1 coulomb is the amount of
electric charge carried by a current of 1 ampere flowing for 1 second. It is also about
6.24×1018 times the charge on an electron. 1 C = 1 A·s
Current
The drift of electrons in an electric field. This is perceived as a flow. It is measured in amperes.
Cycles per second (cps)
An obsolete name for hertz, the standard SI unit. As the name implies, a measurement of
frequency in full cycles of a wave per second. The unit cps (or kilocycles, megacycles, etc.) is
more often seen in older documents.
dB
Decibel. Used to measure logarithmic ratios like signal to noise ratio (SNR), total harmonic
distortion (THD), volume relative to a nominal level. Similar to percent (%) in that it has no
units. dB SPL is used to measure sound levels relative to 20 micro-pascals (µPa). dBu is used to
measure voltage relative to 0.775 V.
DC
Direct current. A constant voltage and a constant current flow in one direction.
Diode
A one way valve for current. Semiconductor diodes typically have a voltage drop of 0.6 V
(silicon) or 0.2V (germanium) when conducting in the forward direction.
DIAGNOSTIC CODE - A number which represents a problem detected by the engine
controller. Diagnostic codes are transmitted for use by on - board
displays or a diagnostic reader so the operator or technician is aware there is a problem and in
what part of the fuel injection system the problem can be found.
DIFFERENTIATOR CIRCUIT - A circuit that consists of resistors and capacitors designed to
change a DC input to an AC output. It is used to make narrow pulse generators and to trigger
digital logic circuits. When used in integrated circuits it is known as an inverter.
DIGITAL IC - lntegrated circuits that produce logic voltage signals or pulses that have only two
levels of output that are either ON or OFF (yes or no). Some component output examples are:
Diagnostic Codes Output, Pulse - Width - Modulated (PWM) Throttle Output, Auxiliary Speed
Output, and Fuel FlowfThrottle Output.
DIODE - An electrical device that will allow current to pass through itself in one direction only.
Also see "Zener diode."
DIRECT CURRENT (DC) - A steady flow of electrons moving steadily and continually in the
same direction along a conductor from a point of high potential to one of lower potential. It is
produced by a battery, generator, or rectifier.
DISCHARGE - To remove electrical energy from a charged body such as a capacitor or battery.
DISTRIBUTOR (IGNITION) - A device which directs the high voltage of the ignition coil to
the engine spark plugs.
DISTRIBUTOR LEAD CONNECTOR - A connection plug in the wires that lead from the
sensor in the distributor to the electronic control unit.
DYER DRIVE - One type of flywheel engaging mechanism in a starting motor.
DAC - Abbreviation for "digital to analog converter." (Back to top)

Damping - Reduction in magnitude of oscillation due to energy being dissipated as heat.

Darlington pair - An amplifier consisting of two bipolar junction transistors with their
collectors connected together and the emitter of one connected to the base of the other. Circuit
has an extremely high current gain and input impedance.

DC - Abbreviation for Direct Current. See direction current.

DC load line - A graph representing all possible combinations of voltage and current for a given
load resistor in an amplifier.

DC offset - The change in input voltage required to produce a zero output voltage when no
signal is applied to an amplifier.

DC power supply - Any source of DC power for electrical equipment.

Dead short - Short circuit having zero resistance.

Decade - A frequency factor of ten.

Decibel - (dB) a logarithmic representation of gain or loss.

Delay time - The time for collector current to reach 10% of its maximum value in a BJT
switching circuit.

DIAC - A diode that conducts elecrical only after its breakover voltage has been reached.

Differential amplifier - An amplifier in which the output is in proportion to the differences

between voltages applied to its two inputs.
Digital - Relating to devices or circuits that have outputs of only two discrete levels. Examples:
0 or 1, high or low, on or off, true or false etc.

Diode - A two terminal device that conducts in only one direction.

DIP - Abbreviation for "dual in line package".

Direct coupling - Where the output of an amplifier is connected directly to the input of another
amplifier or to a load. Also known as DC coupling because DC signals are not blocked.

Direct current - Current that flows in only one direction.

Discharge - Release of energy stored in either a battery or a capacitor.

Discrete component - Package containing only a single component as opposed to an integrated

circuit containing many components in a single package.

Dry cell - DC voltage generating chemical cell using a non liquid (paste) electrolyte.

Dual in-line package - Integrated circuit package having two rows of connecting pins.
Abbreviation = DIP

Eddy current - An electric current induced within the body of a conductor when that conductor
either moves through a non-uniform magnetic field or is in a region where there is a change in
magnetic flux.

Electric charge - Electric energy stored on the surface of a material. Also known as a static
charge.

Electron - A subatomic particle of an atom, with a negative charge, that orbits the positively-
charged nucleus.

Electron flow - Electrical current produced by the movement of free electrons toward a positive
terminal; the direction of electron flow is opposite to that of current.

Electric polarization - A displacement of bound charges in a dielectric when placed in an

electric field.

Electrolytic capacitor - A capacitor having an electrolyte between the two plates. A thin layer
of oxide is deposited on only the positive plate. The oxide acts as the dielectric for the capacitor.
Electrolytic capacitors are polarized and so must be connected in correct polarity to prevent
breakdown.
Electromagnet - A coil of wire usually wound on a soft iron or steel core. When current is
passed through the coil a magnetic field is generated. The core provides an easy path for the
magnetic lines of force. This concentrates the field in the core.

Emitter - The semiconductor region from which charge carriers are injected into the base of a
bipolar junction transistor.

Enhancement-mode MOSFET - A field effect transistor in which there are no charge carriers
in the channel when the gate source voltage is zero.

EMF (E)
Electro-Motive Force. A force for moving electrons. See Voltage.
Ethernet
is a family of frame-based computer networking technologies for local area networks (LAN). It
defines a number of wiring and signaling standards for the Physical Layer of the standard
networking model as well as a common addressing format and a variety of Medium Access
Control procedures at the lower part of the Data Link Layer.
ELECTRICAL FIELD - The region around a charged body in which the charge has an effect.
ELECTRICITY - The flow of electrons from atom to atom in a conductor.
ELECTROCHEMICAL - The relationship of electricity to chemical changes and with the
conversions of chemical and electrical energy. A battery is an electrochemical device.
ELECTRO-HYDRAULIC VALVE - A hydraulic valve actuated by a solenoid through
variable voltage applied to the solenoid coil.
ELECTROLYTE - Any substance which, in solution, is dissociated into ions and is thus made
capable of conducting an electrical current. The sulfuric acid - water solution in a storage battery
is an electrolyte.
ELECTROMAGNET - core of magnetic material, generally soft iron, surrounded by a coil of
wire through which electrical current is passed to magnetize the core.
ELECTROMAGNETIC CLUTCH - An electromagnetic device which stops the operation of
one part of a machine while other parts of the unit keep on operating.
ELECTROMAGNETIC FIELD - The magnetic field about a conductor created by the flow of
electrical current through it.
ELECTROMAGNETIC INDUCTION - The process by which voltage is induced in a
conductor by varying the magnetic field so that lines of force cut across the conductor.
ELECTRON - A tiny particle which rotates around the nucleus of an atom. It has a negative
charge of electricity.
ELECTRON THEORY - The theory which explains the nature of electricity and the exchange
of "free" electrons between atoms of a conductor. It is also used as one theory to explain
direction of current flow in a circuit.
ELECTRONICS - The control of electrons (electricity) and the study of their behavior and
effects. This control is accomplished by devices that resist, carry, select, steer, switch, store,
manipulate, and exploit the electron.
ELECTRONIC CONTROL UNIT (ECU) - General term for any electronic controller. See
"controller:'
ELECTRONIC GOVERNOR - The computer program within the engine controller which
deterines the commanded fuel delivery based on throttle command, engine speed, and fuel
temperature. It replaces the function of a mechanical govnor.
ELECTRONIC IGNITION SYSTEM - A system in which the timing of the ignition spark is
controlled electronically. Electronic ignition systems have no points or condenser, but instead
have a reluctor, sensor, and electronic control unit.
ELEMENT - (1) Any substance that normally cannot be separated into different substances. (2)
The completed assembly of a battery consisting of negative plates, positive plates, and separators
mounted in a cell compartment.
ENGINE CONTROLLER - The electronic module which controls fuel delivery, diagnostic
outputs, back - up operation, and communications with other electronic modules.

FIELD EFFECT TRANSISTOR (FET) - A transistor which uses voltage to control the flow of
current. Connections are the source (input), drain (output) and gate (control).
FIXED RESISTOR - A resistor which has only one resistance value.
FREOUENCY - The number of pulse or wave cycles that are completed in one second.
Frequency is measured in Hertz, as in 60Hz (hertz) per second.
FUNDAMENTAL LAW OF MAGNETISM - The fundamental law of magnetism is that
unlike poles attract each other, and like poles repel each other.
FUSE - A replaceable safety device for an electrical circuit. A fuse consists of a fine wire or a
thin metal strip encased in glass or some fireresistant material. When an overload occurs in the
circuit, the wire or metal strip melts, breaking the circuit.
Farad (F)
The SI unit for capacitance (C). A capacitor is one farad if it has a coulomb (1 C) of charge on it
with a voltage separation of a volt (1 V). 1 F = 1 C/V
FET
Field Effect Transistor. Can be thought of as an Electric Field Transistor. A transistor in which
the voltage at the gate controls the resistance of the channel. (i.e. a FET has voltage-controlled
resistance.) BJT is the other major type of transistor.
FM
Frequency modulation. Changing the frequency of a carrier signal to represent the amplitude of
the original signal.
Forward Biased
The voltage polarity through a part which causes it to conduct current.
Frequency (f)
The number of revolutions (cycles) per unit time. Usually expressed in either radians per second
or cycles per second (Hz).
Farad - The basic unit of capacitance. (Back to top)

Ferrite - A powdered, compressed and sintered magnetic material having high resistivity. The
high resistance makes eddy current losses low at high frequencies.

Ferrite bead - Ferrite composition in the form of a bead. Running a wire through the bead
increases the inductance of the wire.

Ferrite-core inductor - An inductor wound on a ferrite core.

Ferrites - Compound composed of iron oxide, a metallic oxide and ceramic. The metal oxides
include zinc, nickel, cobalt or iron.

Fiber optics - Laser's light output carries information that is conveyed between two points by
thin glass optical fibers.

Field effect transistor - A voltage controlled transistor in which the source to drain conduction
is controlled by gate to source voltage. Abbreviation = FET.

Filament - Thin thread of carbon or tungsten which produces heat or light with the passage of
current.

Filter - Network consisting of capacitors, resistors and/or inductors used to pass certain
frequencies and block others.

Flip flop - A bistable multivibrator. A circuit which has two output states and is switched from
one to the other by means of an external signal (trigger). Abbreviation = FF

Flux - Material used to remove oxide films from the surface of metals in preparation for
soldering.

Forward bias - A PN junction bias which allows current to flow through the junction. Forward
bias decreases the resistance of the depletion layer.

Frequency - Rate of recurrence of a periodic wave. Measured in Hertz (cycles per second).

Full wave rectifier - Rectifier that makes use of the full AC wave in both the positive and
negative half cycles.

Function generator - Signal generator that can produce sine, square, triangle and saw tooth
output waveforms.

Fuse - A protective device in the current path that melts or breaks when current exceeds a
predetermined maximum value.

Generator - Device used to convert mechanical energy to electrical energy. (Back to top)

Giga - Metric prefix for 1 billion.

Ground - An intentional or accidental conducting path between an electrical system or circuit
and the earth or some conducting body acting in place of the earth. A ground is often used as the
common wiring point or reference in a circuit.
Gain
A multiplier of voltage or current.
Ground
Ground is defined as the point in the circuit which is at zero voltage. Voltage is relative, and is
the same throughout a conductor, so any point in the circuit can be defined as ground, and all
other voltages are referenced to it. Usually it is defined as the most negative point in the circuit,
for convenience. Sometimes it is defined in the middle of two bi-polar rails, for "balanced"
circuits. In many cases this circuit point is connected to the Earth (Ground) by some buried
conductor.
G
GATE - A logic circuit device which makes a YES or NO (one or zero) decision (output) based
on two or more inputs.
GENERATOR - A device which converts mechanical energy into electrical energy.
GRID - A wire mesh to which the active materials of a storage battery are attached.
GROUND - A ground occurs when any part of a wiring circuit unintentionally touches a
metallic part of the machine frame.
GROUNDED CIRCUIT - A connection of any electrical unit to the frame, engine, or any part
of the tractor or machine, completing the electrical circuit to its source.
GROWLER - A device for testing the armature of a generator or motor.
Half wave rectifier - A diode rectifier that converts AC to pulsating DC by eliminating either
the negative or the positive alternation of each input AC cycle.

Henry - The basic unit of inductance.

Hertz - Unit of frequency equal to one cycle per second. Abbreviation = Hz.
High-Pass Filter
An analog filter that absorbs low frequencies (f) but allows high frequencies to pass.
Horsepower (hp)
The amount of force F a horse can exert. I don't think it is related to horses anymore. 1 hp = 746
W
H
HYDROMETER - An instrument for measuring specific gravity. A hydrometer is used to test
the specific gravity of the electrolyte in a battery.

IGNITION CONTROL UN IT - The module that contains the transistors and resistors that
controls the electronic ignition.
INDUCTANCE - The property of an electric circuit by which an electromotive force (voltage)
is induced in it by a variation of current either in the circuit itself or in a neighboring circuit.
INDUCTOR - A coil of wire wrapped around an iron core.
INSULATED GATE FIELD EFFECT TRANSISTOR (IGFET) - A diffused transistor which
has an insulated gate and almost infinite gate - channel resistance.
INSULATOR - A substance or body that resists the flow of electrical current through it. Also
see "Conductor:'
INTEGRATED CIRCUIT (IC) - An electronic circuit which utilizes resistors, capacitors,
diodes, and transistors to perform various types of operations. The two major types are Analog
and Digital Integrated Circuits. Also see "Analog IC" and "DigitaI IC."
INTEGRATOR CIRCUIT - A circuit that consists of resistors and capacitors and functions as
a filter which can pass signals only below a certain frequency.
INVERTER - A device with only one input and one output; it inverts or reverses any input.
ION - An atom having either a shortage or excess of electrons.
ISOLATION DIODE - A diode placed between the battery and the alternator. It blocks any
current flow from the battery back through the alternator regulator when the alternator is not
operating.
IC
Integrated circuit. A circuit constructed on one chip of semiconductor, rather than as discrete
components.
Impedance
A more generalized form of resistance. The impedance of a device varies with the frequency of
the electricity applied. A perfect resistor will have a constant impedance for all frequencies.
Capacitors and inductors have varying impedances at different frequencies. Measured in ohms.
Inductor
An inductor is a device that stores energy in a magnetic field. It opposes a sudden change in the
flow of current. A solenoid is usually shaped like a spring or a Slinky.
IC - Abbreviation for integrated circuit. See intergrated circuit.

IC voltage regulator - Three terminal device used to hold the output voltage of a power supply
constant over a wide range of load variations.

IGFET - Insulated gate field effect transistor. Another name for a "MOSFET."

Impedance - The total opposition to the flow of current offered by a circuit. Impedance consists
of the vector sum of resistance and reactance. Measured in ohms (Z).

Incandescence - State of a material when heated to the point where it emits light (red hot or
white hot).

Inductor - Length of conductor used to introduce inductance into a circuit. The conductor is
usually wound into a coil to concentrate the magnetic lines of force and maximize the
inductance. While any conductor has inductance, in common usage the term inductor usually
refers to a coil.

Infrared - Electromagnetic heat radiation whose frequencies are above the microwave frequency
band and below red in the visible band.

Input impedance - Opposition to the flow of signal current at the input of a circuit or load.
Insulated - When a non conducting material is used to isolate conducting materials from one
another.

Insulating material - Material that will prevent the flow of current due to its chemical
composition.

Insulation resistance - Resistance of insulating material. The greater the insulation resistance,
the better the insulation.

Intergrated circuit - Also known as a chip, a small electrical device made of semiconductor
material.

Internal resistance - Every source has some resistance in series with the output current. When
current is drawn from the source some power is lost due to the voltage drop across the internal
resistance. Usually called output impedance or output resistance.

Inverting amplifier - An amplifier that has a 180° phase shift from input to output.

Inverting input - In an operational amplifier (op amp) the input that is marked with a minus
sign. A signal applied at the inverting input will be given 180° phase shift between input and
output.

Jack - Socket or connector into which a plug may be inserted. (Back to top)

JFET - Abbreviation for "junction field effect transistor".

Joule - The unit of work and energy.

Junction - Contact or connection between two or more wires or cables. The area where the p-
type material and n-type material meet in a semiconductor.

Junction diode - A semiconductor diode in which the rectifying characteristics occur at a

junction between the n-type and p-type semiconductor materials.
Joule (J)
The work required to exert a force of a newton (1 N) for a meter (1 m). 1 J = 1 N·m

Kilo - Metric prefix for 1000.

Kilovolt-ampere - 1000 volts at 1 ampere.

Kilowatt-hour - 1000 watts for 1 hour.

Kilowatt-hour meter - A meter used by electric utility companies to measure the amount of
electric power used by a customer.

Kinetic energy - Energy associated with motion.

Kirchhoff's current law - The sum of the currents flowing into a point in a circuit is equal to the
sum of the currents flowing out of that same point.

Kirchhoff's voltage law - The algebraic sum of the voltage drops in a closed path circuit is
equal to the algebraic sum of the source voltages applied.

Lead-acid cell - Cell made up of lead plates immersed in a sulphuric acid electrolyte. An
automobile battery usually consists of six lead-acid cells.

Leakage - Small undesirable flow of current through an insulator or dielectric. (Back to top)

Light-emitting diode (LED) - A semiconductor diode that converts electric energy into
electromagnetic radiation at a visible and near infrared frequencies when its pn junction is
forward biased.

Limiter - Circuit or device that prevents some portion of its input from reaching the output. A
clipper.

Linear - Relationship between input and output in which the output varies in direct proportion to
the input.

Linear scale - A scale in which the divisions are uniformly spaced.

Line regulation - The ability of a voltage regulator to maintain a constant voltage when the
regulator input voltage varies.

Load - A source drives a load. Whatever component or piece of equipment is connected to a

source and draws current from a source is a load on that source.

Load current - Current drawn from a source by a load.

Load impedance - Vector sum of reactance and resistance in a load.

Loading effect - Large load impedance will draw a small load current and so loading of the
source is small (light load). A small load impedance will draw a large load current from the
source (heavy load).

Load regulation - The ability of a voltage regulator to maintain a constant output voltage under
varying load currents.
Load resistance - Resistance of a load.

Logic - Science of dealing with the principle and applications of gates, relays and switches.
LASCR
Light activated silicon controlled rectifier. A light activated SCR.
LDR
Light dependent resistor. As light intensity increases, its resistance decreases.
Length (l)
Distance is measured in meters (m).
Low-Pass Filter
An analog filter that absorbs high frequencies (f) but allows low frequencies to pass.
L
LIGHT EMITTING DIODE (LED) - A solid - state display device that emits infrared light
when a forward - biased current flows through it.
LINES OF FORCE - Invisible lines which conveniently illustrate the characteristics of a
magnetic field and magnetic flux about a magnet.
LIQUID CRYSTAL DISPLAY (LCD) - A display device utilizing a special crystal fluid to
allow segmented displays.

MAGNET - A body which has the property of at. tracting iron or other magnets. Its molecules
are aligned.
MAGNETIC FIELD - That area near a magnet in which its property of magnetism can be
detected. It is shown by magnetic lines of force.
MAGNETIC FLUX - The flow of magnetism about a magnet exhibited by magnetic lines of
force in a magnetic field.
MAGNETIC INDUCTION - The process of introducing magnetism into a bar of iron or other
magnetic material.
MAGNETIC LINES OF FORCE - Invisible lines which conveniently illustrate the
characteristics of a magnetic field and magnetic flux about a magnet.
MAGNETIC MATERIAL - Any material to whose molecules the property of magnetism can
be imparted.
MAGNETIC NORTH - The direction sought by the north pole end of a magnet, such as a
magnetic needle, in a horizontal position. It is near the geographic north pole of the Earth.
MAGNETIC PICKUP ASSEMBLY - The assembly in a self - integrated electronic ignition
system that contains a permanent magnet, a pole piece with internal teeth, and a pickup coil.
These parts, when properly aligned, cause the primary circuit to switch off and induce high
voltage in the secondary windings.
MAGNETIC SOUTH - The opposite direction from magnetic north towards which the south
pole end of a magnet, such as a magnetic needle, is attracted when in a horizontal position. It is
near the geographic south pole of the Earth.
MAGNETIC SWITCH - A solenoid which performs a simple function, such as closing or
opening switch contacts.
MAGNETISM - The property inherent in the molecules of certain substances, such as iron, to
become magnetized, thus making the substance into a magnet
MICROPROCESSOR - An integrated circuit combing logic, amplification and memory
functions.
MILLIAMPERE - 1/1,OOO,OOO ampere.
MOLECULE - A unit of matter which is the smallest portion of an element or compound that
retains chemical identity with the substance in mass. It is made up of one or more atoms.
MOTOR - A device which converts electric energy into mechanical energy.
MUL TIMETER - A testing device that can be set to read ohms (resistance), voltage (force), or
amperes (current) of a circuit.
MUTUAL INDUCTION - Occurs when changing current in one coil induces voltage in a
second coil.
Magnetron
A special form of vacuum tube, typically used as the microwave emitter in a microwave oven, or
in Radar systems.
Meter (m)
The SI unit for distance. The distance light travels in 1/299,792,458 second.
MOSFET
Metal-oxide-semiconductor field effect transistor. An FET that uses a thin layer of oxide (usually
silicon) to insulate the gate terminal from the underlying channel
Maxwell - Unit of magnetic flux. One maxwell equals one magnetic line of force. (Back to top)

Mercury cell - Primary cell using a mercuric oxide cathode, a zinc anode and a potassium
hydroxide electrolyte.

Metal film resistor - A resistor in which a film of metal oxide or alloy is deposited on an
insulating substrate.

Metal Oxide Semiconductor Field Effect Transistor - A field effect transistor in which the
insulating layer between the gate electrode and the channel is a metal oxide layer. Abbreviation =
MOSFET.

Metal oxide resistor - A metal film resistor in which an oxide of metal (such as tin) is deposited
as a film onto the substrate.

Meter - Any electrical or electronic measuring device. In the metric system, it is the unit of
length equal to 39.37 inches.

Mica capacitor - Capacitor using mica as the dielectric.

Microphone - Electro acoustic transducer that converts sound energy into electric energy.

Modulation - Process by which an information signal (audio for example) is used to modify
some characteristic of a higher frequency wave known as a carrier (radio for example).

MOSFET - Abbreviation for "metal oxide field effect transistor" (also known as an "insulated
gate field effect transistor"). See metal oxide field effect transistor.

Multimeter - Electronic test equipment that can perform multiple tasks. Typically one capable
of measuring voltage, current and resistance. More sophisticated modern digital multimeters also
measure capacitance, inductance, current gain of transistors and/or anything else that can be
measured electronically.

Multi segment display - Device made of several light emitting diodes arranged in a numeric or
alphanumeric pattern. By lighting selected segments numeric or alphabet characters can be
displayed.

Mutual inductance - Ability of one inductor's lines of force to link with another inductor.

Network - Combination of interconnected components, circuits or systems. (Back to top)

Neutral - A terminal, point or object with balanced charges. Neither positive or negative.

Neutral atom - An atom in which the number of negative charges (electrons in orbit) is equal to
the number of positive charges (protons in the nucleus).

Neutral wire - The conductor of a polyphase circuit or a single-phase three wire circuit that is
intended to have a ground potential. The potential difference between the neutral and each of the
other conductors are approximately equal in magnitude and equally spaced in phase.

Neutron - Subatomic particle in the nucleus of an atom and having no electrical charge.

Nickel-cadmium cell - A secondary cell that uses a nickel oxide positive electrode and a
cadmium negative electrode.

Node - Junction or branch point in a circuit.

Noise - Unwanted electromagnetic radiation within an electrical or mechanical system.

Normally closed - Designation which states that the contacts of a switch or relay are closed or
connected when at rest. When activated, the contacts open or separated.

Normally open - Designation which states that the contacts of a switch or relay are normally
open or not connected. When activated the contacts close or become connected.

npn transistor - A bipolar junction transistor in which a p-type base element is sandwiched
between an n-type emitter and an n-type collector.

Nucleus - Core of an atom. The nucleus contains both positive (protons) and neutral (neutrons)
subatomic particles.
N
NATURAL MAGNET - A magnet which occurs in nature, such as a lodestone. Its property of
magnetism has been imparted by the magnetic effects of the Earth.
NEGATIVE - Designating or pertaining to a kind of electricity. Specifically, an atom that gains
negative electrons is negatively charged.
NEUTRON - An uncharged elementary particle. Present in all atomic nuclei except the
hydrogen nucleus.
NON-MAGNETIC MATERIAL - A material whose molecules cannot be magnetized.
NORMALLY OPEN and NORMALLY CLOSED - These terms refer to the position taken by
the contacts in a magnetically operated switching device, such as a relay, when the operating
magnet is de. energized.

OHM - The standard unit for measuring resistance to flow of an electrical current. Every
electrical
conductor offers resistance to the flow of current, just as a tube through which water flows offers
resistance to the current of water. One ohm is the amount of resistance that limits current flow to
one ampere in a circuit with one volt of electrical pressure.
OHMMETER - An instrument for measuring the resistance in ohms of an electrical circuit.
OHM'S LAW - Ohm's Law states that when an electric current is flowing through a conductor,
such as a wire, the intensity of the current (in amperes) equals the electromotive force (volts)
driving it, divided by the resistance of the conductor. The flow is in proportion to the
electromotive force, or voltage, as long as the resistance remains the same.
OPEN OR OPEN CIRCUIT - An open or open circuit occurs when a circuit is broken, such as
by a broken wire or open switch, interrupting the flow of current through the circuit. It is
analogous to a closed valve in a water system.
OPERATIONAL AMPLIFIER - A high - voltage gain, low - power, linear amplifying circuit
device used to add, subtract, average, etc.
OVERRUNNING CLUTCH - One type of flywheelengaging member in a starting motor.
Ohm (Ω)
A measure of resistance or impedance. 1 Ω = 1 V/A = 1 W/A2
Op-amp
Short for operational amplifier. An op-amp amplifies the voltage between its two inputs.
Oxidation
A reaction where something loses electrons. Given that oxygen will strip electrons from most
elements, this has historically meant a reaction involving oxygen. A cathode (electron emitter) is
constantly oxidized as it looses electrons.

Ohm - Unit of resistance symbolized by the Greek capital letter omega (W). (Back to top)

Op-amp - Abbreviation for operational amplifier. See operational amplifier.

Open loop gain - The gain of an amplifier when no feedback is present.

Open loop mode - An amplifier circuit having no means of comparing the output with the input.
(No feedback.)

Operational amplifier - A high gain DC amplifier that has a high input impedance and a low
output impedance. Op-amps are the most basic type of linear integrated circuits.

Oscilloscope - An instrument used to display a signal graphically. Shows signal amplitude,

period and wave shape in addition to any DC voltage present. A multiple trace oscilloscope can
show two or more waveforms at the same time for phase comparison and timing measurements.

Output - Terminal at which a component, circuit or piece of equipment delivers current, voltage
or power.

Output impedance - Impedance measured across the output terminals of a device without a load
connected.

Output power - Amount of power a component, circuit or system can deliver to a load.

Overload - Condition that occurs when the load is greater than the system was designed to
handle. (Load resistance too small, load current too high.) Overload results in waveform
distortion and/or overheating. Overload protection - Protective device such as a fuse or circuit
breaker that automatically disconnects a load when current exceeds a predetermined value.

Parallel - Circuit having two or more paths for current flow. Also called shunt. (Back to top)

Peak inverse voltage - (PIV) The maximum rated value of an AC voltage acting in the direction
opposite to that in which a device is designed to pass current.

Peak to peak - Difference between the maximum positive and maximum negative values of an
AC waveform.

Period - Time to complete one full cycle of a periodic or repeating waveform.

Phase - Angular relationship between two waves.

Phase angle - Phase difference between two or more waves, normally expressed in degrees.

Phase shift - Change in phase of a wave form between two points, expressed as degrees of lead
or lag.

Phase shift oscillator - An oscillator that uses three RC networks in its feedback path to produce
the 180° phase shift required for oscillation.

Phosphor - Luminescent material applied to the inner face of a cathode ray tube that when
bombarded with electrons will emit light of various colors.

Photoconductive cell - Material whose resistance decreases or conductance increases when

exposed to light.

Photoconduction - A process by which the conductance of a material is change by incident

electromagnetic radiation in the visible light spectrum.

Photo detector - Component used to detect or sense light.

Photodiode - A semiconductor diode that changes its electrical characteristics in response to

illumination.

Photon - Discrete portion of electromagnetic energy. A small packet of light.

Photoresistor - Also known as a photoconductive cell or light dependent resistor (LDR). See
photoconductive cell.

Piezoelectric crystal - Crystal material that will generate a voltage when mechanical pressure is
applied and conversely will undergo mechanical stress when subjected to a voltage.

Piezoelectric effect - The production of a voltage between opposite sides of a piezoelectric

crystal as a result of pressure or twisting. Also the reverse effect which the application of a
voltage to opposite sides causes a deformation to occur at the frequency of the applied voltage.
(Converts mechanical energy into electrical energy and electrical energy into mechanical
energy.)

Plastic film capacitor - Capacitor in which alternate layers of aluminum foil are separated by
thin films of plastic dielectric.

pnp transistor - A bipolar junction transistor with an n-type base and p-type emitter and
collector.

Polarity - The property of having a positive or negative charge.

Polarized - A component which must be connected in correct polarity to function and/or prevent
destruction. Example: Electrolytic capacitor.

Potential difference - Voltage difference between two points which will cause current to flow in
a closed circuit.

Potential energy - Energy that has potential to do work because of its position relative to others.

Potentiometer - A variable resistor with three terminals. Mechanical turning of a shaft can be
used to produce variable resistance and potential. Example: A volume control is usually a
potentiometer.
Power - Amount of energy converted by a circuit or component in a unit of time, normally
seconds. Measured in units of watts (joules/second).

Power amplifier - An amplifier designed to deliver maximum power output to a load. Example:
In an audio system, it is the power amplifier that drives the loudspeaker.

Power dissipation - Amount of heat energy generated by a device in one second when current
flows through it.

Power factor - Ratio of actual power to apparent power.

Power loss - Ratio of power absorbed to power delivered.

Power supply - Electrical equipment used to deliver either AC or DC voltage.

Power supply rejection ratio - A measure of an op-amps ability to maintain a constant output
when the supply voltage varies.

Primary - First winding of a transformer. Winding that is connected to the source as opposed to
secondary which is a winding connected to a load.

Primary cell - Cell that produces electrical energy through an internal electrochemical action.
Once discharged a primary cell cannot be reused.

Printed circuit board - Insulating board containing conductive tracks for circuit connections.

Programmable UJT - Unijunction transistor with a variable intrinsic stand-off ratio.

Protoboard - Board with provision for attaching components without solder. Also called a
breadboard. Primarily used for constructing experimental circuits.

Pulse - Rise and fall of some quantity (usually voltage) for a period of time.

Pulse fall time - Time for a pulse to decrease from 90% of its peak value to 10% of its peak
value.

Pulse width - Time interval between the leading edge and trailing edge of a pulse at a point
where the amplitude is 50% of the peak value.

PARALLEL CIRCUIT - A circuit in which the circuit components are arranged in branches so
that there is a separate path to each unit along which electrical current can flow.
PERMANENT MAGNET - A magnet which retains its property of magnetism for an indefinite
period.
PIEZO ELECTRIC DEVICE - A device made of crystalline materials, such as quartz, which
bend or distort when force or pressure is exerted on them. This pressure forces the electrons to
move.
PLATE - A solid substance from which electrons flow. Batteries have positive plates and
negative plates.
POLARITY - A collective term applied to the positive (+) and negative ( - ) ends of a magnet or
electrical mechanism such as a coil or battery.
POLE - One or two points of a magnet at which its magnetic attraction is concentrated.
POLE SHOES - Iron blocks fastened to the inside of a generator or motor housing around
which the field or stator coils are wound. The pole shoes may be permanent or electro - magnets.
POSITIVE - Designating or pertaining to a kind of electricity. Specifically, an atom which loses
negative electrons and is positively charged.
POTENTIOMETER - A variable resistor used as a voltage divider.
POWER SWITCH TRANSISTOR - The part responsible for switching off the primary circuit
that causes high voltage induction in the secondary winding in an electronic ignition system.
PRIMARY SPEED SENSOR - An engine speed sensor located inside the actuator housing on
the back of the injection pump.
PRINCIPLE OF TURNING FORCE - Explains how magnetic force acts on a current -
carrying conductor to create movement of an armature, such as in an electric motor.
PRINTED CIRCUIT BOARD - A device used to hold integrated circuit components in place
and provide current paths from component to component. Copper pathways are etched into the
board with acid.
PROTON - A particle which, together with the neutron constitutes the nucleus of an atom. It
exhibits a positive charge of electricity.
PULSE - A signal that is produced by a sudden ON and OFF of direct current (DC) within a
circuit.
PULSE-WIDTH-MODULATED (PWM) - A digital electronic signal which consists of a pulse
generated at a fixed frequency. The information transmitted by the signal is contained in the
width of the pulse. The width of the pulse is changed (modulated) to indicate a corresponding
change in the information being transmitted, such as throttle command.

Q Factor- The quality factor or 'Q' of an inductor or tuned circuit is often used to give an
indication of its performance in a resonator circuit. The Q or quality factor is a dimensionless
number and it describes the damping in the circuit. It also provides an indication of the
resonator’s bandwidth relative to its centre frequency.

RECTIFIER - A device (such as a vacuum tube, commutator, or diode) that converts alternating
current into direct current.
REGULATOR - A device which controls the flow of current or voltage in a circuit to a certain
desired level.
RELAY - An electrical coil switch that uses a small current to control a much larger current.
RELUCTANCE - The resistance that a magnetic circuit offers to lines of force in a magnetic
field.
RELUCTOR - A metal cylinder, with teeth or legs, mounted on the distributor shaft in an
electronic ignition system. The reluctor rotates with the distributor
shaft and passes through the electromagnetic field of the sensor.
RESISTANCE - The opposing or retarding force offered by a circuit or component of a circuit
to the passage of electrical current through it. Resistance is measured in ohms.
RESISTOR - A device usually made of wire or carbon which presents a resistance to current
flow.
RHEOSTAT - A resistor used for regulating a current by means of variable resistance; rheostats
allow only one current path.
RIGHT-HAND RULE - A method used to determine the direction a magnetic field rotates
about a conductor, or to find the north pole of a magnetic field in a coil.
ROTOR - The rotating part of an electrical machine such as a generator, motor, or alternator.
Radar - Acronym for "radio detection and ranging". A system that measures the distance and
direction of objects. (Back to top)

RC time constant - Product of resistance and capacitance in seconds.

Reactance - Opposition to current flow without the dissipation of energy. Example: The
opposition provided by inductance or capacitance to AC current. Symbol "X".

Reactive power - The power value in "volt amps" obtained from the product of source voltage
and source current in a reactive circuit. Also called imaginary power or wattles power.

Receiver - Unit or piece of equipment used to receive information.

Recombination - Process by which a conduction band electron gives up energy (in the form of
heat or light) and falls into a valence band hole.

Rectangular coordinates - A Cartesian coordinate of a Cartesian coordinate system whose

straight-line axes or coordinate planes are perpendicular.

Rectangular wave - Also known as a pulse wave. A repeating wave that only operates between
two levels or values and remains at one of these values for a small amount of time relative to the
other value.

Rectification - Process that converts alternating current to direct current.

Rectifier - Diode circuit that converts alternating current into pulsating direct current.

Regulated power supply - Power supply that maintains a constant output voltage under
changing load conditions.

Regulator - Device or circuit that maintains a desired output under changing conditions.

Relay - Electromechanical device that opens or closes contacts when a current is passed through
a coil.
Relative - Not independent. Compared with or with respect to some other measured quantity.

Relaxation oscillator - Free running circuit that outputs pulses with a period dependent or one
or more RC time constants.

Reluctance - Resistance to the flow of magnetic lines of force.

Resistance - Opposition to current flow and dissipation of energy in the form of heat.
Symbolized "R" and measured in ohms.

Resistive power - Amount of power dissipated as heat in a circuit containing resistive and
reactive components. True power as opposed to reactive power.

Resistor - Component made of material that opposes flow of current and therefore has some
value of resistance.

Resistor color code - Coding system of colored stripes on a resistor to indicate the resistor's
value and tolerance.

Resonance - Circuit condition that occurs at the frequency where inductive reactance (XL)
equals capacitive reactance (XC).

Reverse bias - Bias on a PN junction that allows only leakage current (minority carriers) to flow.
Positive polarity on the n-type material and negative polarity to the p-type material.

Reverse breakdown voltage - Amount of reverse bias that will cause a PN junction to break
down and conduct in the reverse direction.

RF - Abbreviation for "radio frequency."

Rheostat - Two terminal variable resistors used to control current.

RL differentiator - An RL circuit whose output voltage is proportional to the rate of change of

the input voltage.

RL filter - Selective circuit of resistors and inductors that offers little or no opposition to certain
frequencies while blocking or attenuating other frequencies.

RL integrator - RL circuit with an output proportionate to the integral of the input signal.

rms - Abbreviation for "root mean square"

rms value - rms value of an AC sine wave is 0.707 times the peak value. This is the effective
value of an AC sine wave. The rms value of a sine wave is the value of a DC voltage that would
produce the same amount of heat in a heating element.

Rotary switch - Electromechanical device that has a rotating shaft connected to one terminal
capable of making or breaking a connection to one or more other terminals.

Saturation - Condition in which a further increase in one variable produces no further increase
in the resultant effect. In a bipolar junction transistor, the condition when the emitter to collector
voltage is less than the emitter to base voltage. This condition puts forward bias on the base to
collector junction. (Back to top)

Saw tooth wave - Repeating waveform that rises from zero to maximum value linearly drops
back to zero and repeats. A ramp waveform.

Schematic diagram - Illustration of an electrical or electronic circuit with the components

represented by their symbols.

Schmitt trigger - Circuit to convert a given waveform to a square wave output.

Schottky diode - Also known as a "hot-carrier diode" or "surface barrier diode", a high speed
diode that has very little junction capacitance.

Secondary - Output winding of a transformer. Winding that is connected to a load.

Secondary cell - Electrolytic cell used to store electricity. Once discharged may be restored by
recharging by putting current through the cell in the direction opposite to that of discharge
current.

Self biasing - Gate bias for a field effect transistor in which source current through a resistor
produces the voltage for gate to source bias.

Semiconductor - An element which is neither a good conductor nor a good insulator, but rather
lies somewhere between the two. Characterized by a valence shell containing four electrons.
Silicon, germanium and carbon are the semiconductors most frequently used in electronics.

Series circuit - Circuit in which the components are connected end to end so that current has
only one path to follow through the circuit.

Seven segment display - Device made of several light emitting diodes arranged in a numeric or
alphanumeric pattern. By lighting selected segments numeric or alphabet characters can be
displayed.

Shield - Metal grounded cover used to protect a wire, component or piece of equipment from
stray magnetic and/or electric fields.

Short circuit - Low resistance connection between two points in a circuit typically causing
excessive current. Also called a "short."

Silicon-controlled rectifier - (SCR) Three terminal active device that acts as a gated diode. The
gate terminal is used to turn the device on allowing current to pass from cathode to anode.

Silicon controlled switch - An SCR with an added terminal called an anode gate. A positive
pulse either at the anode gate or the cathode gate will turn the device on.

Silicon transistor - A bipolar junction transistor using silicon as the semi conducting material.

Silver mica capacitor - Mica capacitor with silver deposited directly onto the mica sheets
instead of using conductive metal foil.

Single in-line package - Package containing several electronic components (generally resistors)
with a single row of connecting pins.

Single pole double throw - (SPDT) Three terminal switch in which one terminal can be
connected to either one of the other terminals.

Single pole single throw - (SPST) Two terminal switch or relay that can open or close one
circuit.

Single throw switch - Switch containing only one set of contacts which can be either opened or
closed.

Sink - Device such as a load that consumes power or conducts away heat.

Sinusoidal - Varying in proportion to the sine of an angle or time function. AC voltage in which
the instantaneous value is equal to the sine of the phase angle times the peak value.

SIP - Abbreviation for "single in-line package." See single in-line package.

Solder - Metallic alloy used to join two metal surfaces.

Soldering - Process of joining two metallic surfaces to make an electrical contact by melting
solder (usually tin and lead) across them.

Soldering iron - Tool with an internal heating element used to heat surfaces being soldered to
the point where the solder becomes molten.

SPDT - Abbreviation for single pole double throw. See single pole double throw.

SPST - Abbreviation for single pole single throw. See single pole single throw.
Square wave - Wave that alternates between two fixed values for an equal amount of time.

Step-down transformer - Transformer in which the output AC voltage is less than the input AC
voltage.

Step-up transformer - Transformer in which the output AC voltage is greater than the input AC
voltage.

Supply voltage - Voltage provided by a power source.

Switch - Electrical device having two states, on (closed) or off (open). Ideally having zero
impedance when closed and infinite impedance when open.

Switching transistor - transistor designed to change rapidly between saturation and cut-off.
SELF-INDUCTION - Voltage which occurs in a coil when there is a change of current.
SEMICONDUCTOR - An element which has four electrons in the outer ring of its atoms.
Silicon and germanium are examples. These elements are neither good conductors nor good
insulators. Semiconductors are used to make diodes, transistors, and integrated circuits.
SENDING UNIT - A device, usually located in some part of an engine, to transmit information
to a gauge on an instrument panel.
SENSOR - A small coil of fine wire in the distributor on electronic ignition systems. The sensor
develops an electromagnetic field that is sensitive to the presence of metal. In monitors and
controllers, they sense operations of machines and relay the information to a console.
SEPARATOR - Any of several substances used to keep one substance from another. In batteries
a separator separates the positive plates from the negative plates.
SERIES CIRCUIT - A circuit in which the parts are connected end to end, positive pole to
negative pole, so that only one path is provided for current flow.
SERIES-PARALLEL CIRCUIT - A circuit in which some of the circuit components are
connected in series and others are connected in parallel.
SHORT (OR SHORT CIRCUIT) - This occurs when one part of a circuit comes in contact with
another part of the same circuit, diverting the flow of current from its desired path.
SHUNT - A conductor joining two points in a circuit so as to form a parallel circuit through
which a portion of the current may pass.
SLIP RING - In a generator, motor, or alternator, one of two or more continuous conducting
rings from which brushes take, or deliver to, current.
SOLENOID - A tubular coil used for producing a magnetic field. A solenoid usually performs
some type of mechanical work.
SOLID-STATE CIRCUITS - Electronic (integrated) circuits which utilize semiconductor
devices such as transistors, diodes and silicon controlled rectifiers.
SPARK PLUGS - Devices which ignite the fuel by a spark in a spark - ignition engine.
SPECIFIC GRAVITY - The ratio of a weight of any volume of a substance to the weight of an
equal volume of some substance taken as a standard, usually water for solids and liquids. When a
battery electrolyte is tested the result is the specific gravity of the electrolyte.
SPRAG CLUTCH DRIVE - A type of flywheel engaging device for a starting motor.
STARTER MOTOR - A device that converts electrical energy from the battery into mechanical
energy that turns an engine over for starting.
STATOR - The stationary part of an alternator in which another part (the rotor) revolves.
STORAGE BATTERY - A group of electrochemical cells connected together to generate
electrical energy. It stores the energy in a chemical form.
SULFATION - The formation of hard crystals of lead sulfate on battery plates. The battery is
then "sulfated."
SWITCH - A device which opens or closes electrical pathways in an electrical circuit.
SYNCHROGRAPH - An all - purpose distributor tester.

TACHOMETER - An instrument for measuring rotary speed; usually revolutions per minute.
TEMPORARY MAGNET - A magnet which loses its property of magnetism quickly unless
forces act to re - magnetize it.
THERMISTOR - A temperature - compensated resistor. The degree of its resistance varies with
the temperature. In some regulators, it controls a Zener diode so that a higher system voltage is
produced in cold weather, when needed.
TRANSFORMER - A device made of two coil windings that transfers voltage from one coil to
the next through electromagnetic induction. Depending upon the number of windings per coil, a
transformer can be designed to step - up or step - down its output voltage from its input voltage.
Transformers can only function with alternating current (AC).
TRANSIENT VOLTAGE PROTECTION MODULE (TVP) - A device which protects the
engine controller electronics against high energy voltage transients such as alternator load
dumps.
TRANSISTOR - A device constructed of semi - conductors that is used in circuits to control a
larger current by using a smaller current for operation. Its function is the same as a relay.
TRIMMER RESISTOR - A resistor used in applications where only a small resistance change
is needed.
Tantalum capacitor - Electrolytic capacitor having a tantalum foil anode. Able to have a large
capacity in a small package.

Temperature coefficient of frequency - Rate at which frequency changes with temperature.

Tera - (T) Metric prefix that represents 1012.

Terminal - Point at which electrical connections are made.

Thermal stability - The ability of a circuit to maintain stable characteristics in spite of increased
temperature.

Thermistor - Temperature sensitive semiconductor that has a negative temperature coefficient

of resistance. As temperature increases, resistance decreases.

Thermocouple - Temperature transducer consisting of two dissimilar metals welded together at

one end to form a junction that when heated will generate a voltage.

Thermometry - Relating to the measuring of temperature.

Thermostat - Device that opens or closes a circuit in response to changes in temperature.

Thick film capacitor - Capacitor consisting of two thick-film layers of conductive film
separated by a deposited thick-layer dielectric film.

Thick film resistor - Fixed value resistor consisting of thick-film resistive element made from
metal particles and glass powder.

Thin film capacitor - Capacitor in which both the electrodes and the dielectric are deposited in
layers on a substrate.

Time constant - (t) Time required for a capacitor in an RC circuit to charge to 63% of the
remaining potential across the circuit. Also time required for current to reach 63% of maximum
value in an RL circuit. Time constant of an RC circuit is the product of R and C. Time constant
of an RL circuit is equal to inductance divided by resistance.

Toggle switch - Spring-loaded switch that is put in one of two positions either on or off.

TO package - Cylindrical, metal can type of package of some semiconductor components.

Transducer - Device that converts energy from one form to another.

Transformer - Inductor with two or more windings. Through mutual inductance, current in one
winding called a primary will induce current into the other windings called secondaries.

Transformer coupling - Also called inductive coupling. Coupling of two circuits by means of
mutual inductance provided by a transformer.

Transistor - Term derived from "transfer resistor." Semiconductor device that can be used as an
amplifier or as an electronic switch.

Transmission - Sending of information.

Transmitter - Equipment used to achieve transmission.

Triac - Bidirectional gate controlled thyristor similar to an SCR (silicon controlled resistor), but
capable of conducting in both directions. Provides full wave control of AC power.

Triangular wave - A repeating wave that has equal positive going and negative going ramps.
The ramps have linear rates of change with time.

Trigger - Pulse used to initiate a circuit action.

Trimmer - Small value variable capacitor, resistor or inductor used to fine tune a larger value.

UJT - Abbreviation for unijunction transistor. See unijunction transistor. (Back to top)

Unijunction transistor - A three terminal device that acts as a diode with its own internal
voltage divider biasing circuit. Abbreviation = UJT.

VACUUM FLORESCENT DISPLAY (VDC) - An anode - controlled display which emits its
own light. It works like a television tube, directing streams of electrons to strike phosphorescent
segments.
VARIABLE RESISTOR - A resistor that can beadjusted to different ranges of value.
VISCOSITY - The internal resistance of a fluid, caused by molecular attraction, which makes it
resist a tendency to flow.
VOLT - A unit of electrical pressure (or electromotive force) which causes current to flow in a
circuit. One volt is the amount of pressure required to cause one ampere of current to flow
against one ohm of resistance.
VOLTAGE - That force which is generated to cause current to flow in an electrical circuit. It is
also referred to as electromotive force or electrical potential. Voltage is measured in volts.
VOLTAGE REGULATOR - A device that controls the strength of a magnetic field produced
by a generator or alternator. It prevents the battery from being overor undercharged during high -
or low - speed operation of the generator or alternator.
VOLTMETER - An instrument for measuring the force in volts of an electrical current. This is
the difference of potential (voltage) between different points in an electrical circuit. Voltmeters
are connected across (parallel to) the points where voltage is to be measured.
VA - Abbreviation for "volt ampere"

Variable capacitor - Capacitor whose capacitance can be change by varying the effective area
of the plates or the distance between the plates.

Variable resistor - Resistor whose resistance can be changed by turning a shaft. See also
"potentiometer and rheostat."

Volt - Unit of potential difference or electromotive force. One volt is the potential difference
needed to produce one ampere of current through a resistance of one ohm.

Voltage - (V) Term used to designate electrical pressure or force that causes current to flow.

Voltage divider - Fixed or variable series resistor network connected across a voltage to obtain a
desired fraction of that voltage.

Voltage drop - Voltage or difference in potential developed across a component due to current
flow.

Voltage rating - Maximum voltage a component can withstand without breaking down.

Voltage regulator - Device or circuit that maintains constant output voltage (within certain
limits) in spite of changing line voltage and/or load current.

Voltage source - Circuit or device that supplies voltage to a load.

Voltaic cell - Primary cell having two unlike electrodes immersed in a solution that chemically
interacts to produce a voltage.

Volt-ampere - Unit of apparent power in an AC circuit containing capacitive or inductive

reactance. Apparent power is the product of source voltage and current.

Voltmeter - Instrument used to measure difference in potential between two points.

Watt - Unit of electrical power required to do work at the rate of one joule per second. One watt
of power is expended when one ampere of direct current flows through a resistance of one ohm.
In an AC circuit, true power is the product of effective volts and effective amperes, multiplied by
the power factor.

Wavelength - (l) Distance between two points of corresponding phase and is equal to waveform
velocity divided by frequency.

Winding - One or more turns of a conductor wound in the form of a coil.

Wire - Single solid or stranded group of conductors having a low resistance to current flow.
Used to make connections between circuits or points in a circuit.

Wire gauge - American wire gauge (AWG) is a system of numerical designations of wire
diameters.

Wireless - Term describing radio communication that requires no wires between two
communicating points.

Wire wound resistor - Resistor in which the resistive element is a length of high resistance wire
or ribbon usually nichrome wound onto an insulating form.

Work - Work is done any time energy is transformed from one type to another. The amount of
work done is dependent on the amount of energy transformed.
WATT - A unit of measure for indicating the electrical power applied in a circuit. It is obtained
by multiplying the current (in amperes) by the electrical pressure (in volts) which cause it to
flow. That is: watts = amperes x volts.
WATT-HOUR - A unit of electrical energy. It indicates the amount of work done in an hour by
a circuit at a steady rate of one watt. That is, watthours = ampere - hours x volts.
WAVE - A signal that is produced by varying a continuous flow of current within a circuit.
Waveforms can be created by either AC or DC current.
WAVEFORM - A graphical representation ofelectrical cycles which shows the amount of
variation in amplitude over some period of time.
WINDING - The coiling of a wire about itself or about some object. Often identified as a series
winding, a shunt winding, etc.
WIRING HARNESS - Thf3 trunk and branches which feed an electrical circuit. Wires from one
part of the circuit enter the trunk, joining other wires, and then emerge at another point in the
circuit.

X - Symbol for reactance. See reactance.

Y - Symbol for admittance. See admittance.

ZENER DIODE (Reverse Bias Direction Diode) - A semiconductor device that will conduct
current in the reverse direction when the voltage becomes higher than a predetermined voltage.