Glossary
Document Actions
Glossary of Terms
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
ABS -Anti-lock Brake Systems. These systems are designed to help maintain vehicle control in heavy braking situations. They help maintain vehicle control by preventing the tires from skidding. This allows the driver to steer the vehicle instead of skidding out of control.
AC -Alternating Current. This type of current changes it's polarity verses time. The current travels in one direction in a wire, then it stops, changes directions, and repeats the cycle.
Amperes - Current is represented by the upper case letter I (I stands for Intensity) in electrical mathematical equations like "Ohm's Law". In 1881, to honor of French physicist Andre Marie Ampere (1775-1836), the measurement of the quantity of current is done with the units of Amperes; amps for short.
Atom - Each element is in the form of an atom. An atom is comprised of three main particles. In the nucleus of the atom there are typically neutrons and protons. The nucleus is the center of the atom. Orbiting the nucleus are the electrons.
Averaging Meter - Usually an inexpensive meter. This type of meter can measure AC voltage and current; however, it is only accurate when measuring a sine wave like in a wall socket.
Base Units - Base Units refers to numbers with units of measure that do not have a prefix; examples: 12 Volts, 2.5 Amps, and 75 Ohms. Examples of numbers with a unit of measure that has a prefix: 1.2 Mega-Ohms, 25 kilo-Volts, 124 milli-amps, etc.
Battery - An automotive battery has 6 sets of positive and negative plates at 2.1V each. This means an automotive battery has a normal voltage of 12.6V. Batteries produce DC voltage. Batteries supply the current to run the vehicle's electrical systems. The alternator charges the battery.
Compound - A combination of different materials.
Camshaft Position Sensor (CMP) - The CMP is used to synchronize the sequential fuel injection system on an engine. the CMP is also used to monitor camshaft timing on engines with variable cam timing.
Conductor - A material that allows electrical current to pass through it with relative ease. The four best conductors of electrical current are 1. Silver, 2. Gold, 3. Copper, and at a distant 4th, Aluminum.
Continuity - To have continuity indicates that the circuit is not open. Wire strands can break inside the wire's insulation. This type of open circuit cannot be seen but it can be detected with a DMM using the continuity setting.
Crankshaft Position Sensor (CKP) - The CKP is used for a reference signal to trigger the ignition and fuel injection systems. the CKP is also used for engine misfire detection.
Current - The movement of electrons from atom to atom. The measurement of the quantity of current is done with the unit of Amperage; Amps for short. The upper case letter A is used to represent Amperage on a Digital multimeter. Current is sometimes referred to as electricity; however, electricity is a word commonly used to describe a number of subjects. Electricity is a universal word, used by those who really do not know what they are talking about, to describe what we will be learning about in this class.
DC - Direct Current; The current does not change polarity.
Digital Multimeter (DMM) - A multimeter is a device that can take multiple types of measurements. Multimeters vary in what they can measure based on their manufacturer. Multimeters exist that can measure some or all of the following: Volts, Ohms, Amps, Diode Test, Capacitor Test, Transistor Beta, Temperature, Frequency, Pulse Width, Dwell, RPM, etc.
Digitizing - Converting an analog or AC voltage to digital form. The digital representation of the analog or AC voltage depends upon the sampling rate and the number of binary bits the digital converter uses.
Diode - A device that only allows current to travel in one direction in a circuit. There are several different types of diodes.
Distributor Pole Piece Coil - This was the equivalent of a crankshaft position sensor inside of the distributor. It was used to trigger the ignition module to fire each spark plug at the appropriate time.
Duty Cycle - The amount of time per cycle that the voltage level is high (positive duty cycle) or low (negative duty cycle).
E - Represents electromotive force in Ohm's law.
Electromotive force (EMF) - Electrical pressure caused by like charged ions being forced to be together. Electromotive force is represented by the upper case letter E in electrical mathematical equations like "Ohm's Law". The measurement of the quantity of electromotive force is done with the unit of Voltage; volts for short. The upper case letter V is used to represent voltage on a Digital Voltmeter.
Electromagnet - English physicist Dominique Francois Jean Arago discovered that a piece of iron could be magnetized by moving it near a current carrying wire. This is an electromagnet.
Electromagnetic Field - Danish physicist Hans Christian Oersted discovered that a magnetic field is produced around a wire when there is electric current in a wire. A compass needle will move when placed next to a current carrying wire.
Electron - An atom is comprised of three main particles; In the nucleus of the atom there are typically neutrons and protons. Orbiting the nucleus are the electrons; electrons have a negative electrical charge.
Element - To begin any discussion of the electrical fundamentals we must start with the basic building blocks of ourselves and everything around us, the basic elements that we are comprised of. These elements are in the form of an atom. You may recall from previous education that there are over 100 different elements known to exist in the universe. The majority of these elements are naturally occurring, while some are artificially produced by man. To see the periodic table of elements on the Internet, go to www.webelements.com
Frequency - The number of cycles (repetitions) of an electrical waveform in a given amount of time. Hertz (Hz) is the unit of measurement for Frequency. Hertz refers to the number of cycles in one second.
Hertz - Hertz (Hz) is the unit of measurement for Frequency. Hertz refers to the number of cycles in one second.
I - Stands for Intensity in Ohm's Law.
Induction - As English scientist Michael Faraday discovered, a magnetic field exerts a force of attraction or repulsion upon the charge carriers (electrons) in the wire causing (inducing) current (electrical energy). The magnetic field can be from a natural magnet, man-made magnet, or an electromagnet.
Internal Impedance - Refers to the internal resistance of a multimeter. Like resistance, impedance has a unit of measurement of Ohms Any multimeter used on an automobile should have at least ten-million ohms of internal impedance.
Insulator - A material that offers a strong resistance to the passing of electrical current. Examples of insulators are: glass, wood, most plastics and rubber, air, pure water.
Ion - An atom that has lost or gained electrons causing it to be electrically unbalanced. An electrically balances atom will have the same number of protons and electrons.
Kilo - The lower case letter k indicates the resistance being measured is displayed in kilo-ohms (thousand (10^3)). The prefix kilo- is from the Greek word khilioi "thousand".
Load - Electrical Load - Relay, Solenoid, light bulb, motor, etc. The device(s) which consume the electrical energy and convert it to heat, motion, or light.
Mega - The upper case letter M indicates the resistance being measured is displayed in Mega-ohms (million (10^6)). The prefix mega- is from the Greek word megas "great".
Micro- The lower case Greek letter "mu" µ indicates the current being measured is displayed in micro-amps (millionth (10 -6)of an amp) µA. The prefix micro- comes from the Greek word mikros "small".
Milli - The lower case letter m indicates the current or voltage is being measured is displayed in milli-amps (mA) or milli-volts (mV) (thousandths (10 -3) of an amp or volt). The prefix milli- is formed from the Latin word mille "thousand".
Molecules - When elements are combined by chemical forces, they form molecules.
Negative Ion - A negative ion is an atom that has gained one or more electrons. In this state, there are less protons with their positive electrical charge than there are electrons with their negative electrical charge.
Neutron - A neutron is located in the nucleus of an atom; it has no electrical charge.
Ohm's Law - In the mid 1800's German physicist, Georg Simon Ohm noticed the following:
- There is a direct relationship between the amount of electromotive force applied to a circuit and the amount of current in the circuit. In other words, if the EMF in a circuit increases by 10%, the current in the circuit will also increase by 10%.
- There is also a direct inverse relationship between the amount of resistance in a circuit and the current in a circuit. In other words, if the resistance in a circuit increases by 10%, the current in the circuit will decrease by 10%.
He formulated a mathematical equation to represent these relationships. The equation is known as Ohm's law. E = I x R.
Ohms - Resistance is represented by the upper case letter R in electrical mathematical equations like "Ohm's Law". In honor of German scientist Georg Simon Ohm, the measurement of the quantity of resistance is done with the units of Ohms.
Omega - The upper case Greek letter Omega Ω is used to represent Ohms on a Digital Multimeter (DMM).
Permanent Magnet (PM) Generator - A PM generator is comprised of the following parts:
- A stationary coil of wire wrapped around a permanent magnet.
- A permanent magnet.
An external toothed reluctor wheel will rotate very close (typically 0.060") to the PM generator. As the reluctor wheel rotates, the magnetic field strength will increase and decrease with each passing tooth. The fluctuating magnetic field induces AC voltage/current into the coil of wire. The faster the rotational speed of the reluctor wheel, the higher the AC output voltage. The AC voltage/current is read by a computer and translated into a rotational speed based upon the frequency of the AC voltage signal.
Positive Ion - A positive ion is an atom that has lost an electron or electrons. In this state, there are more protons with their positive electrical charge than there are electrons with their negative electrical charge.
Prefix - Attached to the beginning of words to modify their meaning such as Mega, kile, milli, and micro. Examples of numbers with a unit of measure that has a prefix: 1.2 Mega-Ohms, 25 kilo-Volts, 124 milli-amps, etc
Proton - An atom is comprised of three main particles. In the nucleus of the atom there are typically neutrons and protons. Orbiting the nucleus are the electrons. Protons have a positive electrical charge.
R - Stands for Resistance in Ohm's Law.
Rectify - To change an AC voltage waveform into a DC voltage waveform. Alternators have a rectifier bridge to perform this function on automobiles.
Relay - A relay is an electromagnetically controlled switch (set of contacts). A relay has a large coil of wire wrapped around a solid iron core
Resistance - Resistance is an opposition to current. The higher the resistance, the lower the current. The measurement of the quantity of resistance is done with the unit of Ohm. The upper case Greek alphabet letter Omega is used to represent Ohms on a Digital multimeter.
Solenoid - A solenoid is a coil of wire wrapped around a hollow non-magnetic core. The hollow core has a spring loaded moveable iron center which performs mechanical work when it moves. When the solenoid is off, the spring moves the core back to its original position.
Scan-Tool - A hand-held computer which can communicate with on-board computers on an automobile or truck. Scan tools can read diagnostic trouble codes (DTCs), read data lists, command actions to take place, program on-board computers with new instruction sets, etc. every vehicle manufacturer has their own scan tool. Aftermarket scan tools are also available; however, they are limited in their functions when compared to a manufacturer's scan tool.
Semi-Conductor - A material that is neither a good conductor nor a good insulator. Examples of semi-conductors are: Silicon, Boron, and Carbon.
Sine Wave - The most common AC waveform on the planet. Your wall socket at home uses an AC voltage with a sine waveform. A sine waveform is a smoothly transitioning AC voltage which toggles back and forth between positive and negative voltages.
Stepper Motor - The armature of a stepper motor can be rotated an exact number of turns or just a fraction of a turn. Stepper motors are controlled by a computer to position a mechanical device in an exact location. A typical stepper motor can be positioned to 256 different positions.
Switch - An on/off device used to control the voltage or current in a circuit.
Tech-2 Scan Tool - General Motors' version of a scan tool
True RMS Meter - True RMS voltage readings are accurate no matter what the voltage waveform looks like. Other meters are only accurate when reading AC voltages if the voltage waveform is a sine wave, like on a wall socket.
V - Represents voltage on a multimeter screen, in Ohms' law, and other electrical equations.
Voltage - Electromotive force is represented by the upper case letter E in electrical mathematical equations like "Ohm's Law". In honor of Italian physicist Count Alessandro Volta, the measurement of the quantity of electromotive force is done with the units of Voltage; volts for short.
Waveform - If a voltage level could be graphed verses time, it would show the waveform of the voltage.
Wheel Speed Sensor (WSS)- The speed of moving components on an automobile can be monitored with a wheel speed sensor. A wheel speed sensor is a permanent magnet (PM) generator.
Wire - Long, multi stranded, flexible, conductive metal material; usually copper, that is coated with insulation to prevent unwanted current paths (short circuits). Wire does have resistance, although it is usually very small. The resistance of a wire depends upon several factors: its length, the material it is made of, its width, and the temperature of the wire. The hotter a conductor gets, the higher its resistance becomes.
