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Need a quick explanation of a technical term or industry phrase? You’re in the right place.
Our glossary is here to help you make sense of the language we use – from test systems to connectors and everything in between. Clear, simple definitions, minimal jargon.
Glossary A - G
AC (Alternating Current): An electric current in which the flow of charge reverses direction many times a second at regular intervals.
Accuracy: The accuracy of a digital tester is defined as the difference between the reading and the true value for a quantity measured in reference conditions.
Active Power: A term used for power when it is necessary to distinguish among Apparent Power, Complex Power and its components, and Active and Reactive Power.
Actuator: In electrical engineering, the term actuator refers to a mechanism that causes a device to be turned on or off, adjusted or moved, usually in response to an electrical signal. An example is a motor that closes blinds in response to a signal from a sunlight detector. Actuators enable computers to control complex manufacturing processes without human intervention or supervision.
AMM: This is an acronym used by The Boeing Company; it stands for Aircraft Maintenance Manual.
Ammeter: An instrument for measuring the flow of electrical current in amperes.
Ampacity: The maximum amount of electrical current that a device or conductor can carry before sustaining deterioration.
Amperage (Amps/Amperes/Ampacity/Rated Amperage): The standard unit of electrical current; the measurement of the flow rate of electricity. A water hose analogy is helpful here – in terms of water through a hose, amperage would be a measure of the volume of water flowing through the hose.
Ampere-Hour (Ah): A unit of measure for battery capacity; the use of one ampere for one hour. 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 10 hours is said to deliver 50 ampere-hours.
Apparent Power (measured in volt-amps): The product of the applied voltage and current in an ac circuit.
Arc flash: An arc flash is caused by current flowing between two conducting surfaces and most commonly occurs as a result of faulty equipment or poor work practices. Left unchecked, arc flashes release a huge amount of energy in a high-pressure blast, which can result in serious injuries and damage.
ATE: automatic test equipment
ATEX: An abbreviation for “ATmosphere EXplosible”. ATEX is also the abbreviated name of the European Directive 2014/34/EC concerning the placing on the market of explosion-proof electrical and mechanical equipment, components and protective systems. It came into force on 1 July 2003, and all new equipment and protective systems have been subject to it since that date.
Back-to-back connection: In HVDC terms, links used to connect neighboring grids are often referred to as “back-to-back” connections, indicating that the distance between the two grids is minimal. Such connections are able to link independent power grids, including those operating at different frequencies, and enable power to flow from one grid to another. This means that generators on either grid can be used to secure the supply of electricity across the extended network. The connections can also improve voltage and frequency stability in the linked grids. Note: The term “back-to-back connection” is also used to describe a test set-up for electrical devices where a motor and a generator are connected to the same shaft line.
Balanced cable / balanced line: A cable having two identical conductors that carry voltages of opposite polarities and equal magnitude with respect to ground. The conductors are twisted to maintain balance over a distance.
Balanced transmission: A mode of signal transmission in which each conductor carries the signal of equal magnitude, but opposite polarity. A 5 volt signal for example, appears as a +2.5 Volts on one conductor and -2.5 Volts on the other.
Balun: An impedance matching transformer that converts the impedance of one interface to the impedance of another interface. Generally used to connect balanced twisted pair cabling with unbalanced coaxial cabling. The term is derived from “balanced / unbalanced”.
Bandwidth: Bandwidth in electronic communication is the difference between the highest- and the lowest-frequency signal in a given transmission medium. It is measured in hertz (Hz).
BLRT: Bond, Loop and Joint Tester – we recommend the MK Test Systems version! See also BLTU, ExLRT and Bonding.
BLTU: Bond and Loop Tester – as above, we recommend the MK Test Systems version! See also BLRT, ExLRT and Bonding.
Bonding: A method used to produce good electrical contact between metallic parts. Also refers to the grounding bars and straps used in buildings to bond equipment to an approved ground.
BPS: Bits per second.
Braid: Fine wires interwoven to form a tubular flexible structure that may be applied over one or more wires for the purpose of shielding. May also be formed into a flattened conductor to be used as a grounding strap.
Breakdown: Failure of electrical insulation to provide a dielectric barrier to the flow of current.
Breakdown voltage: The voltage at which the electrical insulation between two conductors fails.
Cable: A cable is a set of wires, usually encased in an outer protective jacket. A “cord” would be a cable by this definition so far, but a cable is part of a permanent installation; a cord is more flexible and often has a plug end for a portable appliance or lamp.
Cable Harness: A string of cables and/or wires which transmit informational signals or operating currents (energy). The cables are bound together by clamps, cable ties, cable lacing, sleeves, electrical tape, conduit, a weave of extruded string, or a combination thereof.
Calibration: Adjustment of a device so the output is within a specified range for particular values of the input.
Capacitance: The ability of a device to store an electrical charge.
Capacitor: A multipurpose device that can store electrical charge in the form of an electric field. Capacitors are used to buffer electricity (smooth out peaks) and to guard against momentary voltage losses in circuits (when changing batteries, for example).
Capacitor bank: Several capacitors connected in parallel.
Cathode: The negative electrode that emits electrons or gives off negative ions and toward which positive ions move or collect in a voltaic cell or other such device. Also the term for the negative pole of a battery.
CE: An EU standard of safety, the CE marking on end products indicates compliance with all applicable directives. CE stands for Conformite Europeene.
Circuit: A closed path in which electrons from a voltage or current source flow. Circuits can be in series, parallel, or in any combination of the two.
Circuit breaker: Devices that interrupt high currents to protect electrical equipment from damage caused by current surges, eg, from a short circuit or a
lightning strike. To restore service, the circuit breaker must be reset (closed) after correcting the cause of the overload or failure. Circuit breakers are used in conjunction with protective relays to protect circuits from faults.
Clamp: See coupler.
Conductivity: The capability of a conductor to carry electricity, usually expressed as a percent of the conductivity of a same sized conductor of soft copper.
Conductor: An electrical conductor is any substance through which electrical current can flow. Since electrical current is a process involving the flow of electrons, how well a material conducts electricity depends on its atomic structure and chemical consistency. Copper and aluminium are the most common materials used for electrical wiring, whereas silver is the best conductor but is expensive. Gold is sometimes used for high-quality surface-to-surface contacts. Semi-conductors are materials whose ability to conduct electricity can be controlled. Super-conductors, under special conditions, offer no electrical resistance, so electricity can flow indefinitely.
Connector: A female cord mounted wiring device with the conducting elements recessed behind the mating surface. This type of device is normally wired to be live when nothing is plugged in to it. Therefore, connectors are wired to the source of power.
Converter: An electrical device, comprising a rectifier and inverter, used to alter the voltage and frequency of incoming alternating current in an electrical system. The term may also refer to inverters, rectifiers or frequency converters. (See also Converter station, Inverter, Rectifier, Frequency converter).
Converter station: Special equipment is needed to convert electricity from alternating current (AC) to direct current (DC), or vice versa. High-voltage DC (HVDC) converter stations use power electronic devices called thyristors to make these conversions. (See also HVDC and HVDC Light.)
Coupler: A device for transferring electrical energy from one circuit to another. Also known as a clamp.
Coupling transformer: A coupling transformer is a device that permits two (usually) separate circuits to influence one another. Such a setup can be desirable for control purposes. It can also be used, for example, to inject high frequency signals into power lines for communications purposes.
Creepage distance: The shortest distance between two conductors as measured along the device that separates them. Creepage Distance is normally a design parameter of insulators or insulating bushings.
Current: The rate of flow of electrical energy through a conductor or wire, comparable to the amount of water flowing in a pipe. Electric current is measured in amperes or “amps”.
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.
dBm: Decibels compared to one milliwatt. The higher the dBm, the higher the devices transmit or receive power.
DC: See Direct Current.
Decibel (dB): A unit used to express the magnitude of change in level of electric signal or sound intensity. A voltage ratio of 1 to 10 is equal to -20dB, 10 to 1 to 20dB, 100 to 1 to 40dB and 1000 to 1 to 60dB. A power ratio of 10 to 1 is not 20dB, but 10dB, since power(P) is proportional to the square of voltage(V).
Defence/Defense: One of MK Test Systems’ key industries. Learn more here.
Demand: The average value of power or related quantity over a specified period of time.
Dielectric: 1) Any electrical insulating medium between two conductors. 2) The medium used to provide electrical isolation or separation.
Dielectric constant: A number that describes the dielectric strength of a material relative to a vacuum, which has a dielectric constant of one.
Dielectric strength: The maximum electric field that a pure material can withstand under ideal conditions without breaking down (i.e., without experiencing failure of its insulating properties).
Dielectric test: A test that is used to verify an insulation system. The tests involve the application of a voltage higher than that of the rated voltage for a specified time for the purpose of determining the adequacy against breakdown of insulating materials and spacing under normal conditions.
Dielectric withstand: The ability of insulating materials and spacings to withstand specified overvoltages for a specified time (one minute unless otherwise stated) without flashover or puncture.
Diode: A semiconductor device with two terminals, typically allowing the flow of current in one direction only. The function of a diode is to allow current in one direction and to block current in the opposite direction. The terminals of a diode are called the anode and cathode.
Direct Current (DC): Current which moves in a single direction in a steady flow. Normal household electricity is alternating current (AC) which repeatedly reverses its direction. However, many electronics devices require DC, and therefore must convert the current into DC before using it.
Electrolyte: Any substance (as an acid or salt) that when dissolved (as in water) conducts an electric current. As an example, the sulfuric acid-water solution in a storage battery is an electrolyte.
Electromotive Force (EMF): A difference in potential that tends to give rise to an electric current. Measured in volts.
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.
Farad: A unit of measure for capacitance. One farad is equal to one coulomb per volt.
Ferrite: A ferrimagnetic ceramic non-conductive compound material used to prevent high frequency electrical noise from entering or exiting the equipment.
Ferroresonance: A type of resonance in electric circuits which occurs when a circuit containing a nonlinear inductance is fed from a source that has series capacitance, and the circuit is subjected to a disturbance such as opening of a switch. It can cause overvoltages and overcurrents in an electrical power system and can pose a risk to transmission and distribution equipment, as well as to operational personnel. Also known as nonlinear resonance.
Frequency: The number of complete cycles of a wave-form per second, measured in Hertz (Hz). If a current completes one cycle per second, then the frequency is 1 Hz; 60 cycles per second equals 60 Hz.
Fuse: A safety device consisting of a strip of wire designed to melt and break an electric circuit if the current exceeds a safe level. To restore service, the fuse must be replaced using a similar fuse with the same size and rating after correcting the cause of failure.
Generator: A device that converts one form of energy into another, especially mechanical energy into electrical energy.
Ground: The reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
Ground-Fault Circuit-Interrupter (GFCI): An electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor. Such an imbalance is sometimes caused by current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit.
Glossary H - M
Henry (H): A unit of measure for inductance. If the rate of change of current in a circuit is one ampere per second and the resulting electromotive force is one volt, then the inductance of the circuit is one henry.
Hertz (Hz): A unit of measure for frequency, equal to one cycle per second. Hertz replaces the earlier term of cycle per second (cps). Most international devices are typically 50 hertz, whereas U.S. devices are typically 60 Hertz. In alternating current, a hertz is the number of changes of the negative and positive poles per second.
IEC (International Electrotechnical Commission): The international organization that prepares and publishes standards for all electrical, electronic and related technologies.
Impedance: The measure of the opposition that a circuit presents to a current when a voltage is applied. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
Inductance: The property of a conductor by which a change in current flowing through it creates an electromotive force in both the conductor itself (self-inductance) and in any nearby conductors (mutual inductance). Measured in henry (H).
Inductor: A coil of wire wrapped around an iron core. The inductance is directly proportional to the number of turns in the coil.
Inrush Current: The initial surge of current experienced before the load resistance of impedance increases to its normal operating value.
Insulation: A non-conductive material used on a conductor to separate conducting materials in a circuit.
Insulator: Any material where electric current does not flow freely. Insulative materials, such as glass, rubber, air, and many plastics have a relatively high resistance. Insulators protect equipment and life from electric shock.
Inverter: An apparatus that converts direct current into alternating current.
IP (Ingress Protection) Rating: A two digit code, and an optional letter, specifying the level of protection from foreign objects with the first digit referring to protection from solids and the second digit referring to protection from liquids. The optional letter can be appended to classify only the level of protection against access to hazardous parts by persons or to provide additional information related to the protection of the device.
Jacket: The outer material layer of a cable.
Jitter: The slight movement of a transmission signal in time or phase that can introduce errors and loss of synchronization. More jitter will be encountered with longer cables, cables with higher attenuation, and signals at higher data rates.
Joule (J): A measurement of energy or work. In mechanical systems, it’s the force of one newton, moving an object a distance of one meter. In electronics, it’s the same amount of energy, in electrical units. One joule is one watt of power, applied for one second (a watt-second); or a coulomb of electrical charge raised to a potential of one volt.
Kabelsalat: Ok, so this one isn’t a technical term, but we like it! Kabelsalat is the German word for a tangled mass of wires. Literally, ‘cable salad’. See also “snake’s wedding”.
Kilovolt Ampère (kVA): Apparent power expressed in Thousand Volt-Amps. kVA rating designates the output which a transformer can deliver at rated voltage and frequency without exceeding a specified temperature rise.
Kilovolt Ampère Reactive (kVAR): The measure of additional reactive current flow which occurs when the voltage and current flow are not perfectly synchronized or not in phase.
Kilowatt (kW): Actual power expressed in Kilowatts. Equal to 1000 watts.
Kilowatt-hour (kWh): The product of power in kW and time in hours. Equal to 1000 Watt-hours. For example, if a 100W light bulb is used for 4 hours, 0.4kWhs of energy will be used (100W x 1kW / 1000 Watts x 4 hours). Electrical energy is sold in units of kWh.
L: A symbol used to express inductance. The unit of measure is a “Henry”.
LED: Light Emitting Diode. A semiconductor diode that emits light when conducting current and is used in electronic displays, indoor and outdoor lighting, etc.
Load: Anything which consumes electrical energy, such as lights, transformers, heaters and electric motors.
Load Rejection: The condition in which there is a sudden load loss in the system which causes the generating equipment to be over-frequency. A load rejection test confirms that the system can withstand a sudden loss of load and return to normal operating conditions using its governor. Load banks are normally used for these tests as part of the commissioning process for electrical power systems.
LRT: A Loop Resistance Tester is a portable electronic instrument for measuring the resistance of electronic cable shielding as installed in aircraft, without requiring the cables to be disconnected. It comprises three elements: couplers, joint probes, and an instrument assembly. The couplers are used to measure the loop resistance formed by the shielding in the cable under test and airplane structure. The joint probes are used to measure the resistance of joints in the cable (cable-to-backshell, connector-to-bracket) to isolate bad joints if the loop measurement is out of tolerance. Also see BLRT, BLTU and ExLRT.
Megohmmeter: A testing device that applies a DC voltage and measures the resistance (in millions of ohms) offered by the equipment or conductor’s insulation.
MRO: Maintenance, Repair and Overhaul. A vital support function in the aviation industry, MROs offer a wide variety of services essential to ensuring aircraft remain operational, fully functional and safe.
Mutual Induction: Occurs when changing current in one coil induces voltage in a second coil.
Glossary N - T
Nano satellite (nSat): Miniaturised electrical test switching satellite and one of the component parts in the RTS high speed test system. The nSat brings the test points directly to the UUT, eliminating umbilical cables. Designed for MK Test Systems’ RTS (Real-Time Scanning) harness test system.
OEM: Original Equipment Manufacturer. MK Test Systems provides OEMs with test systems for use on their final assembly lines. We also work with MROs.
Ohm: (Ω) A unit of measure of electrical resistance. One ohm is equivalent to the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.
Ohm’s Law: The mathematical equation that explains the relationship between current, voltage, and resistance. Ohm’s Law is used for calculating voltage drop, fault current and other characteristics of an electrical circuit. U=IR; I=U/R; R=U/I; Where U = Voltage impressed on a circuit, I = current flowing in a circuit and R = circuit resistance.
Ohmmeter: An instrument for measuring the resistance in ohms of an electrical circuit.
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.
Oscilloscope: A device that allows you to see how voltage changes over time by displaying a waveform of electronic signals.
Parallel Circuit: A circuit in which there are multiple paths for electricity to flow. Each load connected in a separate path receives the full circuit voltage, and the total circuit current is equal to the sum of the individual branch currents.
Peak to Peak: The amplitude of the AC wave form from its positive peak to its negative peak.
PF: Power Factor
Phase Angle: The angular displacement between a current and voltage waveform, measured in degrees or radians.
Phase Rotation: Phase rotation defines the rotation in a Poly-Phase System and is generally stated as “1-2-3”, anti-clockwise rotation.
Pigtail: A very short patch cable or wiring adapter. Primarily used in the automotive industries where a longer cable assembly is not needed.
Pin and Sleeve: Common term in reference to an IEC60309 device outbound link.
Plug: A male cord mounted wiring device with the conducting pins protruding and exposed. This type of device should never be wired to make the exposed pins live while unplugged; they should always be ‘dead’ until they are plugged into a power source such as a wall or generator outlet.
Polarized: A plug and connector formed in a way that only allows proper connection.
Polarity: The electrical term used to denote the voltage relationship to a reference potential (+). A collective term applied to the positive (+) and negative (-) ends of a magnet or electrical mechanism such as a coil or battery.
Power: The rate at which electrical energy is transferred by an electric circuit. Measured in Watts.
Power Factor: The ratio of energy consumed (watts) versus the product of input voltage (volts) times input current (amps). In other words, power factor is the percentage of energy used compared to the energy flowing through the wires. Adding capacitors to the system changes the inductive effect of the ballast coils, converting a Normal Power Factor (NPF) to a High Power Factor (HPF) system.
Protective Relay: A relay device designed to trip a circuit breaker when a fault is detected.
Quality Assurance: In lieu of any genuine electrical terms beginning with the letter Q, we’re using this opportunity to highlight how we can help improve your quality assurance. Using our test systems means your products are delivered to your end customer certified as 100% correctly wired.
Quick: Our test systems are quick! They help speed up testing time in several ways, cumulatively saving up to 30% testing time in the case of RTS, our next-generation wire harness test system.
Range: Nominal operating limits, specified by the lowest calibration point to the highest calibration point.
Reactive power: The portion of electricity that establishes and sustains the electric and magnetic fields of AC equipment. Exists in an AC circuit when the current and voltage are not in phase. Measured in VARS.
Real power: The average value of the instantaneous product of volts and amps over a fixed period of time in an AC circuit.
Rectifier: An electrical device that converts an alternating current into a direct one by allowing a current to flow through it in one direction only.
Reference range: A specific range of values of an influence quantity within which the transducer complies with the requirements concerning intrinsic errors.
Reference value: A specified single value of an influence quantity at which the transducer complies with the requirements concerning intrinsic errors.
Reference conditions: Conditions of use for a transducer prescribed for performance testing, or to ensure valid comparison of results of measurement.
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.
Residual current: The algebraic sum, in a multi-phase system, of all the line currents.
Resistance: The opposition to the passage of an electric current. Electrical resistance can be compared to the friction experienced by water when flowing through a pipe. Measured in ohms.
Resistor: A device usually made of wire or carbon which presents a resistance to current flow.
Root-Mean-Square (RMS): The effective value of alternating current or voltage. The RMS value equates an AC current or voltage to a DC current or voltage that provides the same power transfer.
Rotor: The rotating part of an electrical machine such as a generator, motor, or alternator. Used in slip rings, which can be tested using a slip ring tester.
RTS: Real-time scanning. MK’s RTS wire harness test system is modular, and offers high speed testing during harness installation and build.
Self induction: Voltage which occurs in a coil when there is a change of current.
Semiconductor: A solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. Devices made of semiconductors, notably silicon, are essential components of most electronic circuits.
Series-parallel circuit: A circuit in which some of the circuit components are connected in series and others are connected in parallel.
Series circuit: A circuit in which there is only one path for electricity to flow.
Short circuit: When one part of an electric circuit comes into contact with another part of the same circuit, diverting the flow of current from its desired path.
Slip ring: An electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals.
Slip ring tester: Also known as SRT, MK’s specialist test system is a modern upgrade to the legacy slip testers commonly used in the slip ring manufacturing sector.
Snake's wedding: When wires are so severely tangled that there is no end to the beginning. For an example, check behind your TV! See also Kabelsalat.
Solid state circuit: Electronic (integrated) circuits which utilize semiconductor devices such as transistors, diodes and silicon-controlled rectifiers.
Stator: The stator is the stationary part of rotary electromagnetic devices like the alternator, electric motor, or generator.
Terminal: A terminal is the point at which a conductor from an electrical component, device or network comes to an end and provides a point of connection to external circuits. A terminal may simply be the end of a wire or it may be fitted with a connector or fastener. The connection may be temporary, as for portable equipment, or may require a tool for assembly and removal, or may be a permanent electrical joint between two wires or devices.
Transistor: A semiconductor device with three connections, capable of amplification in addition to rectification.
True power: Measured in Watts. The power manifested in tangible form such as electromagnetic radiation, acoustic waves, or mechanical phenomena. In a direct current (DC) circuit, or in an alternating current (AC) circuit whose impedance is a pure resistance, the voltage and current are in phase.
Glossary V - Z
Watt: A unit of electrical power, defined as one joule per second. Wattage is calculated as Voltage x Amperage.
Watt-hour (Wh): A unit of electrical energy equivalent to a power consumption of one watt for one hour.
Wattmeter: The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit.
Waveform: A graphical representation of electrical cycles showing the amount of variation in amplitude over a defined period of time.
Wire Harness: An assembly of electrical wires bound together with insulating materials, used in the electrical system of a machine such as an aircraft or computer. Also known as cable harness, a wiring assembly or wiring loom.