Electrical Instruments Flashcards

A set of vocabulary flashcards covering common electrical measuring tools, their functions, and safety precautions based on the Unit 6 Electrical Instruments lecture.

Digital Multimeter (DMM)

An instrument that measures electrical quantities and displays the values in digital form, commonly used in field work, laboratories, and workshops.

Clamp Ammeter

A tool used to measure AC current without disconnecting the circuit; it displays zero if both live and neutral conductors pass through the clamp simultaneously due to magnetic field cancellation.

Megohmmeter (Megger)

An instrument used to measure high resistance, specifically identified as an important tool for electricians in power plants, transmission, and distribution.

Phase Sequence Meter

A device used to identify the phase rotation (order of voltages) and detect open phases in a three-phase system.

Continuity Test

A procedure to check if a connected wire between two devices is closed (connected) or open.

Common Input Terminal (COM)

The terminal on a DMM where the black test lead is plugged in.

$V\Omega$ Terminal

The input terminal on a DMM used for the red test lead when measuring voltage, resistance, or testing diodes.

$$600V$$

The maximum input voltage that must not be exceeded under any circumstances when using the digital multimeter.

Buzzer Function

A setting on a DMM used for continuity testing where a tone is heard for a short circuit and nothing is heard for an open circuit.

$$120^\circ$$

The phase difference between voltages in a standard three-phase system.

RST

The phase sequence labeling that indicates a clockwise rotation.

TSR

The phase sequence labeling that indicates a counter-clockwise rotation.

Phase Rotation

The order of voltages in a three-phase system, usually labeled as R, S, and T.

Open Phase Indication

A condition on a phase sequence meter where only one phase light glows, identifying a faulty or disconnected phase.