Measuring Instruments and Bridge Circuits Practice Flashcards

A set of vocabulary flashcards covering measuring instruments, bridge circuit types, and their applications as described in the Topic 7 lecture notes.

Wattmeter

An electrical instrument used to measure electric power in a circuit, expressed in watts ($W$).

Current Coil (CC)

A coil in a wattmeter connected in series with the load to measure current.

Voltage Coil (VC)

A coil in a wattmeter connected in parallel with the load to measure voltage.

Electrodynamometer wattmeter

A type of wattmeter used for both DC and AC power measurement consisting of fixed field coils and a moving coil.

Induction wattmeter

A type of wattmeter used for AC power measurement only, featuring components like a shunt magnet, series magnet, and aluminum disc.

Real Power ($P$)

The actual power consumed by electrical devices to perform useful work, measured in Watt ($W$).

Reactive Power ($Q$)

Power that oscillates back and forth between the source and reactive components without being used for useful work, measured in Voltage-Ampere Reactive ($VAR$).

Digital clamp-type power meter

A device that measures current without direct electrical contact based on electromagnetic induction using a split-core transformer or Hall-effect sensor.

Field Strength Meter

A device used to measure the intensity of electromagnetic fields, typically in the radio frequency (RF) spectrum, calibrated in units like $dB ext{μV/m}$.

Stroboscope

A device used to make a moving object appear stationary or slow-moving by emitting flashes of light at a specific frequency to measure rotational speed.

Stroboscopic effect

The principle of operation where a flash rate is synchronized with the motion of an object to make it appear stationary.

Phase Meter

An electronic instrument used to measure the angular displacement or phase difference between two periodic signals, expressed in degrees or radians.

Q Meter

An instrument used to measure the quality factor ($Q$) of inductors and capacitors based on the principle of resonance in an LC circuit.

Quality Factor ($Q$)

The ratio of reactive power to real power in a circuit, represented as Q = rac{ ext{Energy Stored}}{ ext{Energy Dissipated}}.

Resonance

The condition achieved by adjusting frequency so an external driving force matches the natural frequency of a system, allowing maximum oscillation amplitude.

Energy Meter

A device used to measure the total amount of electrical energy consumed by a load over time, typically expressed in kilowatt-hours ($kWh$).

Braking Magnet

A permanent magnet in an energy meter that creates opposing torque to ensure the aluminum disc speed is proportional to energy consumption.

Megger Meter

Commonly known as a megohmmeter, it is an instrument used to measure the high insulation resistance of electrical equipment to ensure safety.

pH Meter

A scientific instrument used to measure the acidity or alkalinity of a solution by determining hydrogen ion concentration on a scale of $0$ to $14$.

Bridge Circuit

An electrical circuit topology where two branches are bridged by a third branch, used to convert impedance variations into voltage variations.

LCR Meter

Electronic test equipment used to measure the inductance ($L$), capacitance ($C$), and resistance ($R$) of electronic components.

Wheatstone Bridge

An electrical circuit used to measure an unknown electrical resistance by balancing two legs, one of which contains the unknown component.

Wien Bridge Circuit

An AC circuit used to determine the value of unknown frequency or to measure capacitance.

Maxwell Bridge Circuit

A bridge used to measure an unknown inductance of low $Q$ value in terms of standardized Resistance and Capacitance.

Hays Bridge Circuit

A bridge used to measure the inductance of coils with a high $Q$ factor.

Schering Bridge Circuit

A type of AC circuit used to measure capacitance, dielectric loss, and power factor of an unknown capacitor.

Kelvin / Thomson Bridge Circuit

A bridge used to measure unknown resistances having values less than $1 ext{ }Ω$.

H-Bridge Circuit

An electronic circuit that switches the polarity of voltage applied to a load, commonly used in robotics to run DC motors forwards or backwards.

Diode Bridge Circuit

A bridge rectifier circuit of four diodes used to convert alternating current (AC) to direct current (DC).

Null Condition

The balanced state of a bridge where no current flows through the detector, defined by the equation $R_2 R_3 = R_1 R_4$.

Bridge Resolution

The smallest change in resistance in one arm of the bridge that causes an offset voltage equivalent to the resolution of the detector.

Lead compensation

A method to reduce errors from long lead wires by introducing resistance changes equally into both arms of the bridge circuit.

Strain Gauge

Sensors that measure physical changes like pressure or force by converting deformation into measurable electrical signals in a Wheatstone bridge.

Gauge factor ($GF$)

The ratio of fractional change in electrical resistance to the fractional change in length (strain).

RTD (Resistance Temperature Detector)

A sensor, often made of platinum, whose electrical resistance changes predictably with temperature.

LDR (Light-Dependent Resistor)

A passive resistive sensor, also known as a photoresistor, which converts visible light levels into a change in resistance.