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In the majority of instruments, damping is provided by eddy currents.

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Description :

In a PMMC instrument, the damping provided is :  (A) air damping (C) eddy current damping (B) fluid damping (D) magnetic damping using a magnet

Answer :

In a PMMC instrument, the damping provided is : eddy current damping 

Description :

A control system having unit damping factor will give  (1) Oscillatory response (2) Undamped response (3) Critically damped response (4) No response

Answer :

1

Description :

Ideally, the damping torque should be  (1) Proportional to velocity of the moving system and operating current.  (2) Proportional to the velocity of the moving system but independent of operating current.  (3) Independent of the velocity of the moving system and proportional to the operating current.  (4) Independent of the velocity of the moving system and operating current.

Answer :

Ideally, the damping torque should be Proportional to the velocity of the moving system but independent of operating current. 

Description :

Eddy current damping cannot be used for moving iron instrument because

Answer :

Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument

Description :

Answer :

Damping of the Ballistic galvanometer is made small to get first deflection large.

Description :

Answer :

The disc of an instrument using eddy current damping should be of conducting and non-magnetic material.

Description :

What do you mean by secondary instruments?

Answer :

The instruments which will give the direct readings are called secondary instruments

Description :

Answer :

Commonly used instruments in power system measurement are induction.

Description :

Answer :

Operating torques in analogue instruments are deflecting, control and damping.

Description :

Permanent magnet moving coil instruments are used for

Answer :

PMME are mostly used for measuring voltage and current.

Description :

Answer :

The power factor of a single phase load can be calculated if the instruments available are three ammeters or three voltmeters.

Description :

Answer :

The switch board instruments should be mounted in vertical position.

Description :

Answer :

According to application, instruments are classified as switch board, portable.

Description :

Answer :

The use of absolute instruments is merely confined within laboratories as standardizing instruments.

Description :

How instruments are classified?

Description :

What is electrical instruments?

Description :

The damping winding in synchronous motor is generally used to?

Answer :

The damping winding in synchronous motor is generally used to provide starting torque and prevent hunting.

Description :

List the different methods to produce damping torque.

Answer :

Methods of providing damping torque in indicating type instruments: 1) Air friction damping. 2) Fluid friction damping. 3) Eddy current damping.

Description :

Describe with neat diagram air friction damping. 

Answer :

Air Friction Damping: Here air trapped in the chamber works as damping medium for the piston movement connected to the spindle. The piston moves in the air chamber. The clearance between piston and ... will be the damping torque, bringing the pointer to the equilibrium position quickly. 

Description :

Given a unity feedback system with G(s)=k/s (s+4), the value of k for damping ratio of 0.5 is

Answer :

Given a unity feedback system with G(s)=k/s (s+4), the value of k for damping ratio of 0.5 is 16

Description :

The damping factor of a particular system is unity, the system response will be

Answer :

The damping factor of a particular system is unity, the system response will be critically damped

Description :

Explain the essential toques in analog type measuring instruments.

Answer :

List of torques in analog instruments:  1. Deflecting torque  2. Controlling / Restraining torque.  3. Damping torque.  1. Deflecting torque: To create deflection proportional to ... the speed higher will be the damping torque bringing the pointer to the equilibrium position quickly. 

Description :

List three types of errors in measuring instruments. Give reasons of occurring for any one of them.

Answer :

Types of errors in measuring instruments:  A) Gross error: These are due to mistakes on the part of person using the instrument.  B) Systematic Error: i) Instrumental Error: These ... multiplying factor.  C) Random error: These persist even after gross and systematic errors are removed.

Description :

List out any four effects of electric current used in measuring instruments & write name of meter working on it.

Answer :

Effects of Electric Current used in measuring instruments:  1. Magnetic Effect: PMMC and Moving Iron type Ammeters, voltmeter and Dynamometer type wattmeters etc.  2. Electromagnetic induction ... . Electrostatic effect: Voltmeters.  5. Hall Effect: Flux meter, Poynting vector wattmeter.

Description :

Describe systematic errors in measuring instruments. 

Answer :

Systematic errors: -  ➢ Instrumental Error: These errors are caused due to the mechanical structure of measuring instrument.  a) Inherent shortcomings of instruments: Instrument may read ... or electrostatic fields.  ➢ Observational Error: Parallax errors, incorrect multiplying factor. 

Description :

List any four effects employed in measuring instruments.

Answer :

Effects Employed in Measuring Instruments: 1. Magnetic Effect 2. Electromagnetic induction 3. Heating effect 4. Electrostatic effect 5. Hall Effect 

Description :

Electrical Measuring Instruments

Answer :

Electrical Measuring Instruments

Description :

Compare analog and digital instruments .

Answer :

Parameter Analog Instrument Digital Instrument  1 Principle The instrument that displays analog signals is called as on analog instrument.  The instrument that displays ... , etc. Logical analyzer, signature analyzer, computers, microprocessor based instruments, etc. 

Description :

calibration and the need of calibration for measuring instruments.

Answer :

Calibration - It is a process of estimating the value of a quantity by comparing that quantity with a standard quantity.    Need of calibration: - Calibration defines the accuracy and ... aim of calibration is to minimize any measurement uncertainty by ensuring the accuracy of test equipment.

Description :

Advantages of digital instruments

Answer :

1. They are having high input impedance, so there is no loading effect 2. They are having higher accuracy 3. An unambiguous reading is obtained 4. The output can be interfaced with external equipment 5. They are available in smaller size . 

Description :

State the effect of dead zone on instruments.

Answer :

It is the largest change in input during which the output remains constant. So during dead zone, even if input changes, output remains the same.

Description :

Define: i) Range ii) Span of instruments

Answer :

i) Range: It is defined as the difference between Greatest and Smallest value of the data or reading of the instrument.  ii) Span: It is defined as the algebraic difference between the upper and lower range values

Description :

State two purposes of calibration of measuring instruments.

Answer :

Purposes of calibration of measuring instruments: - The purpose of calibration is to ensure that readings of an instrument are consistent with other instruments. It is also important in determining the ... will need to be calibrated periodically to make sure it can function properly and safely. 

Description :

State the meaning of secondary instrument. Classify secondary instruments.

Answer :

Secondary instruments: - Gives reading directly of the quantity being measured. - Calibrated with respect to absolute instruments  Classification of Secondary instruments:  1. Depending on the ... on permissible error: i) Standard meters ii) Substandard meters iii) First grade instruments.

Description :

Define following terms related to measuring instruments: i) Sensitivity ii) Selectivity.

Answer :

i) Sensitivity: It is the ratio of the change in output signal to the change in input signal of quantity being measured.  ii) Selectivity: It is the term to describe fulfillment of the requirements of measurement by an instrument to be suitable for use in a given situation. 

Description :

Compare primary and secondary instruments.

Answer :

Primary instruments  Secondary instruments  Gives magnitude of quantity in terms of physical constants of instrument  Gives reading directly of the quantity measured.  Need no calibration  ... .  e.g. magnetic meter, induction meter, hotwire meter and electrostatic meter 

Description :

State the material used for moving coil and former for PMMC instruments. 

Answer :

Material Used for Moving Coil and Former for PMMC Instruments:  Material used for moving coil: Copper  Material used for Former: Aluminium

Description :

Standard Commands for Programmable Instruments (SCPI)

Answer :

Standard Commands for Programmable Instruments (SCPI) SCPI stands for Standard Commands for Programmable Instruments it is often pronounced as Skippy. SCPI is a instrument language that control the ... is for storing data in instrument. Display : for presentation.

Description :

Answer :

In moving coil meters, damping is provided by eddy current disk.

Description :

Eddy current damping is normally used in the instruments of (a) Induction type (b) Moving iron type (c) Permanent magnet moving coil type (d) Nothing can be said 

Answer :

Permanent  magnetic  moving  coil  instrument.

Description :

Answer :

Air friction damping is used in the instruments which is: Moving iron

Description :

In moving iron instruments, eddy current damping cannot be used as  (a) They have a strong operating magnetic, field (b) They are not normally used in vertical position (c) They need a large damping force, which can only be provided by air friction (d) The introduction of a permanent magnet required for eddy current damping would distort the existing weak operating magnetic field

Answer :

In moving iron instruments, eddy current damping cannot be used as The introduction of a permanent magnet required for eddy current damping would distort the existing weak operating magnetic field

Description :

The best and efficient damping in Analog instruments is : - a) Air Friction damping b) Fluid Friction damping c) Eddy Current damping d) None of the above

Answer :

The best and efficient damping in Analog instruments is : - Eddy Current damping

Description :

The most efficient from of damping employed in electrical instruments is (1) Air friction (2) Fluid friction (3) Eddy current (4) None of the above 

Description :

Answer :

In a meggar controlling torque is provided by coil.

Description :

Answer :

In a portable instrument, the controlling torque is provided by spring.

Description :

Answer :

The electrical power to a meggar is provided by permanent magnet D.C. generator.

Description :

Answer :

Dynamometer type moving coil instruments are provided with pneumatic damping

Description :

Answer :

Moving iron and PMMC instruments can be distinguished from each other by looking at: Scale

Description :

Control systems are generally designed with damping  a) less than one  b) greater than one c) equal to one d) with any value depending upon system requirement

Answer :

Control systems are generally designed with damping  less than one 

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