Analog Type Meters: Basic Meter Movements Quiz

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Questions and Answers

What is the purpose of the Kelvin Bridge modification to the Wheatstone bridge?

To measure AC resistances instead of DC resistances

To increase the sensitivity of the galvanometer

To increase the range of resistance measurements

To eliminate the effects of contact and lead resistances when measuring very low resistances (correct)

What is the principle of operation of the Wheatstone bridge?

An AC voltage source provides the source of current to the resistance network, and an ammeter is connected between the parallel branches to measure the current.

A DC voltage source provides the source of current to the resistance network, and a voltmeter is connected between the parallel branches to measure the voltage difference.

A DC voltage source provides the source of current to the resistance network, and a null detector (usually a galvanometer) is connected between the parallel branches to detect a condition of balance. (correct)

An AC voltage source provides the source of current to the resistance network, and a null detector (usually an oscilloscope) is connected between the parallel branches to detect a condition of balance.

What is the relationship between the sensitivity of the galvanometer and the unbalanced condition of the Wheatstone bridge?

The sensitivity of the galvanometer is determined by the resistance values in the Wheatstone bridge, and has no relationship to the unbalanced condition.

The sensitivity of the galvanometer is directly proportional to the deflection of the pointer when the bridge is unbalanced. (correct)

The sensitivity of the galvanometer is independent of the unbalanced condition of the Wheatstone bridge.

The sensitivity of the galvanometer is inversely proportional to the deflection of the pointer when the bridge is unbalanced.

What is the primary application of the Wheatstone bridge?

Measurement of DC resistances of various types of wires Signup and view all the answers

What is the purpose of the Murray Loop Test, which is a type of loop test used with the Wheatstone bridge?

To locate ground faults in sheathed cables Signup and view all the answers

What is the typical range of resistance measurements that can be made using the Kelvin Bridge?

1 microohm to 1 milliohm Signup and view all the answers

Which of the following meter movements utilizes a 'taut band' suspension system for increased sensitivity?

D'Arsonval Meter Signup and view all the answers

Which meter movement is suitable for both direct current (DC) and alternating current (AC) measurements?

Electrodynamometer Signup and view all the answers

Which meter movement is based on Hans Oersted's discovery of the relationship between current and magnetism?

All of the above Signup and view all the answers

Which meter movement is commonly used in applications such as 'standards' meters, transfer instruments, wattmeters, and frequency meters?

Electrodynamometer Signup and view all the answers

Which meter movement consists of a fixed coil with many turns and two iron vanes placed inside the fixed coil?

Iron Vane Movement Signup and view all the answers

Which of the following meter movements is widely used for measuring direct current (DC) or voltage and resistance?

D'Arsonval Meter Signup and view all the answers

What is the primary purpose of the Varley Loop Test?

To locate shorts between conductors or faults to ground in conductors Signup and view all the answers

Which bridge is used to measure the impedance of an inductive circuit?

Opposite Angle Bridge Signup and view all the answers

What is the purpose of the Schering Bridge?

To measure capacitance, often used for phase angles very nearly 90 degrees Signup and view all the answers

Which bridge is used extensively as a feedback arrangement for a circuit called the Wien Bridge Oscillator?

Wien Bridge Signup and view all the answers

Which bridge is used in laboratories to measure the impedance of both capacitance and inductive circuits at higher frequencies?

Radio frequency Bridge Signup and view all the answers

What is the standard arm of the Schering Bridge typically composed of?

A capacitor, usually a high-quality mica capacitor Signup and view all the answers

Which of the following is NOT a function of a sine wave generator?

Generating square or rectangular waveforms Signup and view all the answers

What is the primary purpose of a distortion analyzer?

To analyze the non-linear characteristics of active and passive devices in an amplifier Signup and view all the answers

Which of the following statements about function generators is NOT true?

They are designed to measure the relative amplitudes of frequency components in a complex waveform Signup and view all the answers

What is the typical output impedance of radio frequency generators?

50 ohms Signup and view all the answers

What is the defining characteristic of a pulse or square wave generator?

It generates an output signal that is either square or rectangular in form, with a different duty cycle Signup and view all the answers

What is the primary function of a wave analyzer?

To measure the relative amplitudes of frequency components in a complex waveform Signup and view all the answers

What is the primary function of a frequency selective voltmeter?

To tune to the frequency of one signal while rejecting all other signal components Signup and view all the answers

Which instrument is primarily used to measure the total harmonic content in waveforms?

Harmonic distortion analyzer Signup and view all the answers

What is the primary advantage of a Fourier analyzer over a spectrum analyzer?

Fourier analyzers use digital signal processing techniques to provide more accurate and stable measurements Signup and view all the answers

Which of the following instruments provides a real-time display of the amplitude of all signals in its frequency range?

Real-time spectrum analyzer Signup and view all the answers

What is a significant advantage of Fourier analyzers over other instruments mentioned?

They can interface relatively easily with computers or digital systems Signup and view all the answers

Which of the following instruments provides a graphical display of a signal's energy distribution as a function of frequency?

Spectrum analyzer Signup and view all the answers

Study Notes

DC Bridges

A DC type bridge accurately measures resistances with each branch containing two series elements usually resistors.
A DC voltage source provides the source of current to the resistance network.
A null detector usually a galvanometer is connected between the parallel branches to detect a condition of balance.
For a balanced bridge, the galvanometer reading is zero.

Wheatstone Bridge

A DC type bridge that measures DC resistances of various types of wires.
Used to locate faults in cables.
Murray Loop Test is used to locate ground faults in sheathed cables.
Varley Loop Test is a modification of Murray Loop test.

Kelvin Bridge

A modified version of the Wheatstone bridge that eliminates the effects of contact and lead resistances.
Displays high degree of accuracy in measuring resistance of range 1ohm to 1u ohm.
Uses a second set of arms and is referred to as Kelvin Double Bridge.

AC Bridges

Basically a Wheatstone bridge, with arms that are impedances instead of purely resistances.
Used to measure capacitance, inductance, and impedance.

Angle Bridge

Measures the impedance of a capacitive circuit.
Sometimes called the capacitance comparison bridge or the series resistance capacitance bridge.

Opposite Angle Bridge

Measures the impedance of an inductive circuit.
Known as Hay Bridge.

Maxwell Bridge

Determines an unknown inductance with capacitance standards.
Also known as Maxwell-Wien Bridge.

Wien Bridge

Measures the equivalent series components or the equivalent parallel components of an impedance.
Used extensively as a feedback arrangement for a circuit called the Wien Bridge Oscillator.

Radio Frequency Bridge

Used to measure the impedance of both capacitance and inductive circuits at higher frequencies.
Measurement technique used in this bridge is known as the substitute technique.

Schering Bridge

Used to measure capacitance.
Often used to measure insulating properties such as for phase angles very nearly 90 degrees.

Frequency Selective Voltmeter

Measures the voltage or energy of a signal as a function of frequency.
Other names include carrier frequency voltmeters, selective level meters, and wave analyzers.

Spectrum Analyzer

Presents graphically the energy distribution of a signal as a function of frequency.
Provides information about the voltage or energy of the signal as a function of frequency.

Fourier Analyzer

Based on the calculation of the discrete Fourier transform using an algorithm called the fast Fourier Transform.
Uses digital signal-processing technique to provide measurements that go beyond the capabilities of spectrum analyzer.

Signal Generators

Sine Wave Generator: generates continuous sine wave that the frequency of the wave is made variable.
Audio Frequency Generator: a sine wave generator whose frequency is limited to audible frequency range.
Radio Frequency Generators: provides output signal over a wide range of frequencies from approximately 30 KHz to nearly 3000 MHz.
Pulse and Square wave generators: generates an output signal that is either square or rectangular in form but with a different duty cycle.
Function Generators: provides a variety of output waveforms over a wide range of frequencies.

Signal Analyzers

Distortion Analyzers: measures the signal distortion due to the nonlinear characteristics of the active and passive devices the amplifier.
Wave analyzer: a tunable voltmeter used to measure the various frequency components of a signal.

Basic Meter Movements

Permanent Magnet Moving Coil (PMMC) meter movement: uses a “taut band” suspension system which provides a more sensitive meter movement.
Electrodynamometer: consists of a moving coil called “armature” that is free to move within a magnetic field set by two stationary field coils.
Iron Vane Movements: consists of a fixed coil of many turns and two iron vanes placed inside the fixed coil.

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Description

Test your knowledge on basic meter movements in analog type meters, specifically focusing on the D'Arsonval Meter and the Permanent Magnet Moving Coil (PMMC) meter movement. Learn about the relation between current and magnetism discovered by Hans Oersted.