Electrical Definitions
- A, ampere or amp: The basic unit of electric current.
- AC, alternating current: An electric signal in which the current and voltage vary in a repeating pattern over time; the most common type of voltage.
- Analog meter: A mechanical measuring device using a needle moving across a graduated scale or dial.
- Auto ranging: A DMM that automatically selects the range with the best resolution and accuracy in response to the application.
- Calibration: Zeroing of an instrument to a known standard.
- Capacitance: Ability of a component to hold an electrical charge, usually stated in microfarads.
- Capacitor: Electronic component which stores energy and then discharges it; blocks DC and allows AC to pass through.
- Clamp-on: DMM with jaws that allow it to fit around a conductor to measure AC or DC current without breaking the circuit.
- Contact: A connection between two conductors that allows a flow of current.
- Continuity: The continuous path for current flow in a closed circuit.
- Current: The flow of an electrical charge through a conductor; measured in amperes or amps.
- DC, direct current: an indirectional, steady voltage; typically produced through electromagnetism, chemicals (batteries), light, heat or pressure.
- Data hold: Feature of DMM that allows continued display of last reading taken after probes have been removed.
- Diode: Electronic device in circuits that allows current to flow easily in only one direction and blocks flow in the opposite direction.
- DMM, digital multimeter: An instrument that uses an LCD typically capable of measuring voltage, current and resistance.
- F, farad: The basic unit of capacitance.
- Frequency: The number of cycles per second that a wave form repeats; measured in hertz. (Line voltage in U.S. is 60 Hz.)
- Ground: A large conducting body (earth) used as a common return for current in a circuit.
- H, hertz: One cycle per second; the unit of frequency.
- Harmonics: A signal with a frequency which is a multiple of the fundamental frequency (60Hz); may damage or degrade the performance of electrical devices.
- Harmonic distortion: Diminishes power quality; caused by non-linear loads such as variable speed motor drives, electronic lighting ballasts and computers.
- Impedance: Total opposition to current flow; includes resistance, capacitance and reactance.
- Load: Any device which consumes power in a circuit.
- Manual ranging: DMM that requires the user to manually select the range using the meter’s dial.
- Min/max: Feature that allows a meter to capture and store the highest and lowest readings during a specific measurement.
- Ohm: The basic unit of resistance, specified as equal to that of a conductor in which one amp of current is produced by one volt of potential across
- its terminals.
- OL, overload: Signal amplitudes or frequencies above the specified limits of the instrument; typically displayed as “OL” on the display of a DMM.
- Peak hold: Feature of DMM that allows retention of highest reading in a series of measurements.
- Polarity: The positive or negative direction of DC voltage or current.
- Resolution: Increments in value that can be displayed by a DMM; the greater the resolution the more precise the readout.
- Resistance: Opposition to current; measured in ohms.
- Sleep mode: Automatically shuts down unit not in use to preserve battery life.
- Short: Any connection that has relatively low resistance or any resistance between two points below a preselected threshold.
- True RMS meter: DMM that has the True RMS feature, allowing for accurate measurement of AC voltage in environments with harmonics (see
- harmonics).
- V, volt: The unit of electrical pressure; one volt is the potential difference needed to cause one amp of current to pass through one amp of resistance.
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