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The pointer of an indicating instrument should be very light.

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

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Eddy current damping cannot be used for moving iron instrument because

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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

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A moving iron instrument can be used for both D.C. and A.C.

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A moving-coil permanent-magnet instrument can be used as flux-meter by eliminating the control springs.

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A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

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A Pyrheliometer is an instrument to measure :  (A) temperature of solar photovoltaic cell  (B) intensity of direct solar radiation at normal incidence  (C) intensity of indirect solar radiation  (D) efficiency of a solar photovoltaic cell

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A Pyrheliometer is an instrument to measure : intensity of direct solar radiation at normal incidence 

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A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is (A) 1 Ω (B) 1.001 Ω (C) 0.5 Ω (D) 10 Ω

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A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is 1.001 Ω

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If an instrument has cramped scale for larger values, then it follows logarithmic law.

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Meggar is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another.

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

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

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Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

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Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

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Instrument transformers are potential transformers, current transformers.

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The rectifier instrument is not free from frequency error.

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A multirange instrument has multiple shunt or series resistances inside the meter.

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The gravity controlled instrument has crowded scale because current is proportional to sine of deflection angle.

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The ratio of maximum displacement deviation to full scale deviation of the instrument is called?

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The ratio of maximum displacement deviation to full scale deviation of the instrument is called linearity.

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The scale of a rectifier instrument is linear.

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

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What is the definition of a primary instrument?

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A moving coil instrument is used as an ohmmeter. The indicating scale of the meter will be Hyperbolic.

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The force required to move the pointer in an indicating instruments is

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The force required to move the pointer in an indicating instruments is deflecting force

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An instrument which detects electric current is known as?

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An instrument which detects electric current is known as galvanometer.

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The moving system of an indicating type of electrical instrument is subjected to (a) a deflecting torque (b) a controlling torque (c) a damping torque (d) All of the above

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need of calibration and explain the procedure to calibrate the instrument.

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Need of calibration: Every measuring device degrades over time due to normal wear and tear. These changes can be caused by various reasons such as electric or mechanical shock or a hazardous manufacturing ... different magnitude are used to calculate the resistance based on ohm's law.

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feature of PMMC instrument. 

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Consumes less power Great accuracy. High torque to weight ratio

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What modifications are necessary if ac is applied to a PMMC instrument?

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Write any four advantages of instrument transformer.

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Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.

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State the meaning of secondary instrument. Classify secondary instruments.

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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.

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State the function of former and control spring in PMMC instrument.

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Function of Former: To support the coil and provide eddy current damping.  Function of Control Spring: To provide control torque or force and in some instruments springs can be used as current leads.

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‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

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The direction of force exerted on moving coil depends on the direction of current flowing through moving coil. If the direction of magnetic field is kept constant, it produces unidirectional torque if the current is ... on the coil in one cycle to zero. Hence the meter cannot read A.C. quantities.

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Describe spring control method of producing controlling torque in measuring instrument. Write any two properties required for spring material.

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A)Spring control method: As shown in the figure, the inner ends of the both springs are attahced to the spindle, while outer end of upper spring is attached to the lever and outer ... of spring material: 1.Non Magnetic material 2.Low specific resistance 3.Low temperature coefficient of resistance

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Name the different torque and their function in measuring instrument.

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List of torques in analog instruments:  1. Deflecting torque  2. Controlling / restraining torque.  3. Damping torque.  1. Deflecting torque:  - To create deflection of pointer ... .  - Bring the pointer to standstill quickly.  - To minimize oscillations about final position. 

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Give the classification of the errors used in measuring instrument & state the reason for their occurrence.

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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. 

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Name the material used for :- (i) Moving coil (ii) Permanent magnet in PMMC instrument.

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(i) Material used for Moving coil: Copper, Aluminum( some times)  (ii) Permanent magnets are made of special alloys such as :  Aluminum-Nickel-Cobalt (Alnicos)  Strontium-Iron  Neodymium-Iron-Boron  Samarium-Cobalt.

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State the meaning of absolute instrument and secondary instrument. 

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Absolute instruments:   These instruments read the quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant. The actual value under measurement can be calculated ... of operation (b) Depending upon permissible percentage error. (c) Depending upon application.

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State the advantages of instrument transformer in using for extension of range of meters. 

Answer :

Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.

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Explain magnetic effect employed in measuring instrument.

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Magnetic Effect:  I) In PMMC meters:  ➢ When a current is passed through a conductor, magnetic field is produced round the conductor. Due to this field when current ... field it experiences a mechanical force.  Examples: Electrodynamometer type instruments, Induction type instrument. 

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State the function of controlling torque in electrical measuring instrument.

Answer :

Function of controlling torque  1. The function is to opposes the deflection force and increases with the increase in the deflection of the moving system, to limit its movement. 2. and brought ... set a position where the two opposing forces i.e. deflection and controlling forces are equal. 

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Explain construction & working of attraction type M.I. instrument with neat diagram.

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1. Moving element: a small piece of soft iron in the form of a vane or rod.  2. In Attracted type a cylindrical coil or solenoid which is kept fixed. An oval-shaped soft-iron piece are ...   9. When = the pointer will be stable & we can get correct reading of the electrical quantity

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Why energy meter is integrating type measuring instrument?

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Energy Meter is Integrating Type Measuring Instrument: Energy meter is used for measurement of energy, which is obtained by integration (summation) of power supplied over the particular time duration, hence it the integrating type measuring instrument. 

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Write any two advantages of MI type instrument.

Answer :

Advantages of MI Type Instrument: 1. These are robust in construction. 2. Used for both A.C. as well as D.C. measurements. 3. These are economical. 4. These possess high operating torque 5. These are simple in construction hence can be easily handled.

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State working principle of PMMC instrument.

Answer :

Working Principle of PMMC Instrument: When current carrying conductor is placed in a constant magnetic field, it experiences a force proportional to the current and produces proportional deflection torque. 

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Write difference between absolute & secondary instrument.

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Absolute Instrument Secondary Instrument 1. These give magnitude of quantity in terms physical constants of instruments 1. These give reading directly of the quantity at the time of ... Raleigh current balance. 6. Examples - ammeter, voltmeter, amperehour meter, wattmeter etc.

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Compare PMMC & MI instrument.

Answer :

MI Instrument  PMMC Instrument  It works on the principles of magnetism.  It works on the principle of DC motor Deflection torque is proportional to square of current  Deflection ... , Voltmeter and Watt meter  Can be used as voltmeter, Ammeter, Galvanometer, ohmmeter  

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The largest change of input quantity for which there is no output of instrument is called ______ A) Dead time B) Dead input C) Dead output D) Dead zone

Answer :

The largest change of input quantity for which there is no output of instrument is called Dead zone

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For the indicating instrument the preferred damping condition is  a damping coefficient of 0.8 to 1.

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The damping torque must operate only when the moving system of the indicating instrument is: Actually moving

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Answer :

An instrument to be used for measurement and control should preferably have Linear output and fast response

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Indicating instruments should be   (a) undamped (b) critically damped (c) over damped (d) under damped 

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