DEFINITIONS & TERMINOLOGY

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

A

Absolute Zero: -459.67°F or -273.15°C or 0 Kelvin. The temperature where thermal energy is at minimum.


Actuator: The mechanism of a switch which operates the contacts.


Alternating Current: (AC); Electrical current that changes (or alternates) in magnitude and direction of the current at regular intervals.


American National Standards Institute:ANSI; ~LINK~


Amp: (ampere)The basic unit of current in an electrical circuit. One ampere is the rate of flow of electric current when one coulomb of charge flows past a point in the circuit in one second. Symbolically characterized by the letter "I" and sometimes "A" when used in formulas.


Ampere:A unit of electrical current named after French physicist André Marie Ampère (1775-1836), also see "amp".


Amplifier: An electrical circuit that increases the power, voltage or current of an applied signal.


Anode: A positive (+) electrode. The point where electrons exit from a device to the external electric circuit.


AWG: "American Wire Gauge" system used to determine wire size.


B

Beta: The current that is gained by a transistor when it is connected in a common emitter circuit.


Break: The act of the opening of an electrical circuit.


Bridge Rectifier: A full-wave rectifier where the diodes are connected in a bridge circuit. This allows the current to the load during both the positive and negative alternating of the supply voltage.


BTU: "British Thermal Unit", the amount of thermal energy required to raise one pound of water 1degree F. One BTU is equal to .293 watt hours. One kWh is equal to 3412 BTUs.


C

Canadian Standards Administration:CSA ~LINK~


Capacitor: A device used to store electrical energy in an electrostatic field until discharge.


Cathode: A negative (-) electrode. The point of entry of electrons into a device from an external circuit. The negative electrode of a semiconductor diode.


Celsiuss: A temperature scale. Also known as centigrade. Sea level water will freeze at 0°C and will boil at 100°C.


Charge: The measured amount of electrical energy that represents the electrostatic forces between atomic particles. The nucleus of an atom has a positive charge (+) and the electrons have a negative charge(-).


Chatter: The rapid on/off cycling of a relay caused by improper signal or adjustment, faulty contacts, or other malfunction.


Circuit: A full path of electrical current from a voltage source that passes completely from one terminal of the voltage source to another.


CMV: "Common Mode Voltage." The voltage which is tolerable between signal and ground.


Conductance: The measure of the ability of a material or substance to carry electrical current.


Conduction: The moving of electricity or heat through a conductor.


Conductor: A material used to conduct electricity or heat.


Conduit: A tube, pipe or trough that carries and protects electric wiring.


Coulomb: A unit of electric charge. The amount of charge conveyed in one second by one ampere.


Current: The rate at which electricity flows, measured in amperes, 1 ampere = 1 coulomb per second.


Current Proportioning: In a temperature controller it is the output form that provides a current proportional to the amount of control that is required. Commonly it is the 4 to 20 milliamp current proportioning band that is used in the electronics industry.


Cycle: or Hertz; The measurement of the time period of one alternating electric current. In the United States this is commonly 60 cycles per second, or 60 Hertz.


Cycle Time: The time it takes for a controller to complete one on/off cycle.


D

Delta: In a three phase connection all three phases are connected in series thus forming a closed circuit.


Dilectric: Non-conducting material used to isolate and/or insulate energized electrical components.


Diode: A device having two terminals and has a low resistance to electrical current in one direction and a high resistance in the other direction.


Direct Current: (DC); Electrical current that flows consistently in one direction only.


E

Efficiency: Output power divided by input power, (work performed in ratio to energy used to produce it).


Electric circuit: An arrangement of any of various conductors through which electric current can flow from a supply current.


Electricity: A form of energy produced by the flow of particles of matter and consists of commonly attractive positively (protons [+]) and negatively (electrons [-]) charged atomic particles. A stream of electrons, or an electric current.


Electrochemistry: Chemical changes and energy produced by electric currents.


Electrode: An anode (+) or cathode (-) conductor on a device through which an electric current passes.


Electroduct: An interconnected arrangement of parts for carrying high-voltage electricity.


Electrodynamic: The interaction of magnetism and electrical current.


Electrokinetics: The behavior of charged particles and the steady motion of charge in magnetic and electric fields.


Electrolysis: Electric current passing through an electrolyte which produces chemical changes in it.


Electrolyte: An electrically conductive fused salt or a solution where the charge is carried by ionic movement.


Electromagnet: A coil of wire wound about a magnetic material, such as iron, that produces a magnetic field when current flows through the wire.


Electromagnetic field: Electric and magnetic force field that surrounds a moving electric charge.


Electron: A fundamental negatively (-) charged atomic particle that rotates around a positively (+) charged nucleus of the atom.


Environmental Protection Agency: EPA; ~LINK~


F

Factory Mutual:FM; ~LINK~


Farad: The unit for capacitance. A capacitor that stored one coulomb of charge with one volt across it will have a value of one farad.


Field cell: Commonly used in generators and motors, it is an electromagnet formed from a coil of insulated wire that is wound around a soft iron core.


Field-Effect Transistor (FET): A three terminal semiconductor device. In a "FET" the current is from source to drain because a conducting channel is formed by a voltage field between the gate and the source.


Filament: The element inside a vacuum tube, incandescent lamp or other similar device.


Filter: A circuit element or components that allows signals of certain frequencies to pass and blocks signals of other frequencies.


Fluorescent: The quality of having the ability to emit light when struck by electrons or another form of radiation.


Flux: The rate of transfer of energy.


Forward resistance: When there is current through a semiconductor p-n junction it is the resistance of a forward-biased junction.


Forward Voltage: The voltage that is applied across a semiconductor junction to permit forward current through that junction and the device. Forward voltage is also known as "bias."


Frequency: Also known as Hertz, it is the number of complete cycles of periodic waveform that occur during a time period of one second.


G

Gain: The increase of the power level, current or voltage of a signal. In an amplifier it is the ratio of the output to the input signal levels.


Ground: A reference point at zero potential with respect to the earth. In an electronic circuit it is the common return path for electric current. A conducting connection between the earth and an electrical circuit or electrical equipment. Also, the negative side of DC power supply.


Grounded: A connected path to earth or to a conductive body that has a reference potential to earth.


Grounded Conductor: A circuit conductor that is grounded to become part of the electric circuit by design and intent.


Grounding Conductor: The conductor that is used by intent to connect the grounded circuit of an electrical wiring system or equipment to a grounding electrode with reference to earth.


H

Hard Wired: That part of a circuit which is physically interconnected.


Hazardous Location: An area in which combustible or flammable mixtures are or could be present.


I

I: Intensity. The commonly used symbol used to represent Amperes when used in formulas. I = Intensity = Current = Amps = Amperes.


Impedance: The opposition to electrical flow.


Infrared: The form of radiation used to make non-contact temperature measurements. In the electromagnetic spectrum it is the area beyond red light from 760 nanometers to 1000 microns.


Ingress Protection Ratings: European environmental ratings. Similar to NEMA ratings in the USA. IP;*site has NEMA comparisons ~LINK~


Institute of Electrical and Electronics Engineers: IEEE; ~LINK~


Interface:The method by which two devices or systems are connected and interact with each other.


International Brotherhood of Electrical Workers:IBEW; ~LINK~


International Electrotechnical Commission:IEC; ~LINK~


International Organization for Standardization:ISO; ~LINK~


Intrinsically safe: A device, instrument or component that will not produce any spark or thermal effects under any conditions that are normal or abnormal that will ignite a specified gas mixture. Electrical and thermal energy limits are at levels incapable of causing ignition. It is common practice to use external barriers with intrinsically safe installations.


Instrument Society of America:ISA; ~LINK~


Isothermal: A process that is kept at a constant temperature.


J

Joule: The basic of thermal energy. The work done by the force of one newton acting through a distance of one meter.


K

Kilovolt: kV; One thousand volts.


Kilovolt amperes: Kva; One thousand volt amps.


Kilowatt: Kw; One thousand watts.


Kilowatt Hour: Kwh; One thousand watt-hours.


L

Lag: The time delay between the output signal and the response time of the receiver of the signal.


Latching logic: The modification of a signal that causes the output to remain energized until it is released by intent.


Latent heat: The amount of heat needed to convert one pound of water to one pound of steam. Latent heat is expressed in BTU per pound.


Leakage current: A small current leaking from an output device in the off state caused by semiconductor characteristics.


Light Emitting Diode: LED; A solid state light source component that emits light or invisible infrared radiation.


Load: The electrical demand of a process. Load can be expressed or calculated as amps (current), ohms (resistance) or watts (power).


M

M: Symbol for Mega, one million.


Magnetic Blow-out Switch: A switching device used in switching high DC loads. It contains a small permanent magnet which deflects arc in order to quench it.


Magnetic Field: A region of space that surrounds a moving electrical charge or a magnetic pole, in which the electrical charge or magnetic pole experiences a force that is above the electrostatic ones associated with particles at rest.


Magnetic Flux: Expressed in webers, it is the product of the average normal component of the magnetic intensity over a surface and the area of that surface.


Make: To close an electrical circuit. To establish an electrical circuit through the closing of a contact, switch or other related device.


Manual Reset Switch: A switch in a controller that manually resets after exceeding the controllers limit.


Maximum Load Current: see; "Maximum Power Rating".


Maximum Operating Temperature: The maximum temperature at which a device can be safely operated.


Maximum Power Rating: The maximum watts that a device can safely handle.


Mean Temperature: The average temperature of a process.


Microamp: One millionth of an amp.


Micron: One millionth of a meter.


Microvolt: One millionth of a volt.


Mil: One thousandth of an inch.


Milliamp: mA; One thousandth of an amp.


Millimeter: mm; One thousandth of a meter.


Millivolt: mV; One thousandth of a volt. The difference in potential needed to cause a current of one milliampere flow through a resistance of one ohm.


Modulated Light Source Control: MLS; A photoelectric control that operates on pulsed infrared radiation at a specific frequency, and responds only to that frequency of pulse. MLS is used frequently in areas where ambient light may cause problems with other types of sensors.


Momentary switch: A switch with contacts that are made with actuating force and released when that force is removed.


Mueller Bridge: A highly accurate bridge configuration that is used to measure three-wire RTD thermometers.


N

National Electrical Code: NEC: A set of regulations pertaining to electrical installation and design in the interest of the protection of life and property. The NEC is adopted by NFPA and approved by ANSI. It is the preferred standard of guidelines used by most electrical regulatory boards in the USA.


National Electrical Manufacturers Association:NEMA; ~LINK~


National Fire Protection Association:NFPA; ~LINK~


N.C.: Normally Closed.


N.O.: Normally Open.


O

Occupational Safety & Health Administration:OSHA; ~LINK~


Ohm: The unit by which electrical resistance is measured. One ohm is equal to the current of one ampere which will flow when a voltage of one volt is applied


Ohmeter: A meter used to measure electrical resistance in units of ohms.


On/Off Controller: A controller whose action is either fully on or off.


Open Circuit: An electrical circuit that is not "made". Contacts, switches or similar devices are open and preventing the floe of current.


Operating Temperature: The range of temperature over which a device may be safely used. The temperature range which the device has been designed to operate.


OR Logic: The output that is produced when one or more inputs are present.


Output: The energy delivered by a circuit or device. The electrical signal produced by the input to the transducer.


P

Phase: The time based relationship between a reference and a periodic function.


Phase Proportioning: A form of control where the power supplied to a process is controlled by limiting the phase angle of the line voltage.


PID: A three mode control consisting of time Proportioning, Integral and Derivative rate action.


Plasma: An ionized gas containing about equal numbers of positive and negative charges, which is a good conductor of electricity, and is affected by a magnetic field.


Polarity: Magnetically, opposite poles, north and south. In electricity, oppositely charged poles, positive and negative.


Potentiometer: A variable resistor.


Power Dissipation: The amount of power that is consumed and converted to heat.


Power Supply: The part of a circuit that supplies power to the entire circuit or part of the circuit. Usually a separate unit that supplies power to a specific part of the circuit in a system.


Process Meter: A panel meter with zero and span adjustments, commonly scaled for signals such as 1-5 volts, 4-20mA, etc.


Proximity Sensor: A sensor or switch with the ability to detect it’s relationship to a metal target without making physical contact.


Proximity Switch: see; "Proximity Sensor".


PSIA: Pounds per square inch absolute. Pressure commonly in reference to vacuum.


PSID: Pounds per square inch differential. The difference in pressure between two points.


PSIG: Pounds per square inch gage. Pressure in relationship to the ambient air pressure>


Pulse: A rise and fall of voltage, current, or other faction that would be constant under normal conditions. A pulse that is intentionally induced will have a finite duration time.


Q

Quality Control: Inspection, analysis and action required to ensure quality of output.


Quantum: One of the very small discrete packets into which many forms of energy are subdivided.


Quantum Electronics: Applying molecular physics to electronics.


Quap: A hypothetical nuclear of a quark plus an antiproton.


Quark: A hypothetical basic subatomic nuclear particle believed to be the basic component of protons, neutrons, etc.


Quartz: A form of silicone dioxide. Commonly used in the making of radio transmitters and heat resistant products.


Quartziodine Lamp: A high-intensity incandescent lamp with a quartz bulb containing an inert gas of iodine or bromine vapor.


Quasiparticle: A unit of energy in solid-state physics with mass and momentum but that does not exist as a free particle.


Q-value: The amount of energy released in a nuclear reaction. It is expressed in atomic mass units, or in million electron volts (MEV).


R

Rectifier: A device that converts AC voltage to pulsating DC voltage.


Relay: A Solid State relay is a switching device that completes or interrupts a circuit electrically and has no moving parts. A Mechanical relay is an electromechanical device that closes contacts to complete a circuit or opens contacts to interrupt a circuit.


Resistance: The resistance to electrical current. Resistance is measured in ohms.


Response Time: The amount of time it takes for a device to react to an input signal.


RFI: Radio Frequency Interference.


Rheostat: A variable resistor.


Ripple: A fluctuation in the intensity of a steady current.


Root Mean Square: RMS; AC voltage that equals DC voltage that will do the same amount of work. For an AC sine wave it is 0.707 x peak voltage.


RTD: Resistance Temperature Detector.


S

SCR: Silicone Controlled Rectifier.


Series Circuit: A circuit which may have one or many resistors and/or other various devices connected in a series so that the current has only one path to follow.


Supply Current: Current Consumption. The amount of amps or milliamps needed to maintain operation of a control or device.


Supply Voltage: The range of voltage needed to maintain operation of a control or device.


System International: SI; The standard metric system of units.


T

Thermistor: An electrical resistor composed of semiconductor material, whose resistance is a known rapidly varying function of temperature.


Thermocouple: Two dissimilar metals connected at a point, that produce an electrical current whose magnitude is dependent upon the temperature at the junction point.


Thermoelectricity: Electrical energy produced by the action of heat.


Threshold Response: Response to the change in the level of the input signal.


Thyristor: A solid-state switching device for semiconductors to convert AC current in one of two directions controlled by an electrode.


Time Delay Before Availability: The delayed period of time when outputs are turned off when power is initially applied.


Transducer: A device that transfers power or energy from one system to another, such as taking a physical quality and changing it to an electrical signal.


Transient: A sudden and unwanted increase or decrease of supply voltage or current.


Transient Protection: Protective circuitry to guard against spikes that might be induced on the supply line.


Transistor: A device incorporating semiconductor material and suitable contacts capable of performing electrical functions (such as voltage, current or power amplification) with low power requirements.


Triac: A solid-state switching device used in switching AC wave forms.


U

UHF: Ultra High Frequency


Underwriters Laboratories:UL; ~LINK~


V

Vacuum: Pressure that is less than atmospheric pressure.


Vector: The magnitude and time phase of a quantity, represented by a plotted line.


Velocity: The speed or time rate of change of displacement.


VF: Variable Frequency.


VHF: Very High Frequency.


Volt: Voltage; The unit of electromotive force (EMF) that causes current to flow. One volt causes a current of one amp through a resistance of one ohm.


Voltage Drop: The difference in potential measured between two points caused by resistance or impedance.


Voltmeter: A meter used to measure units of volts.


VOM: Volt-ohm Meter.


W

Watt: The unit of power. One watt equals one joule per second, 1/746th horsepower.


Watt-hour: The power of one watt operating for one hour, and equal to 3,600 joules.


Weber: The standard unit of magnetic flux.


Working Standard: The standard that is used to make comparison measurements or calibrations.


X

XFMR: Symbol used to denote transformer.


XMTR: Symbol used to denote transmitter.


X ray: An electromagnetic radiation produced when the inner satellite electrons of heavy atoms have been excited by collision with a stream of fast electrons return to their ground state, giving up the energy previously imparted to them.


Y

Y: Symbol used for wye configuration for three phase electrical connections.


Z

Zener Diode: A silicone semiconductor that maintains a fixed voltage in a circuit.


Zener Effect: The pronounced curvature in reverse voltage current that is characteristic of a diode.


Zero Adjustment: The adjustment of a display that results are zero on the display corresponding to a non-zero signal.

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Every effort is taken in order to maintain accuracy in the information contained within this web site. However, the author of this site shall not be held liable for the use of the information or of it’s consequences. Although all of the information is believed to be accurate you are encouraged to consult other sources for additional information or clarification. If you are a student your instructor may have very specific terminology that is required to be used for your particular field of study and therefore you should consult your textbooks and study notes for that information. It is my hope that this site will be both educational and beneficial to those of you who use it. I welcome your comments and suggestions in regards to this site. Thanks for visiting!

Henry J. Bacon

Email: voltampkva@aol.com