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Question
difference between null and deflecting instrument.
 Question Submitted By :: Instrumentation
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
The accuracy of these two instruments depends on different
things. For the Null type ins it depends on the linearity
and calibration of the spring, while for the second it
relies on the calibration of the weights. As calibration of
weights is much easier than careful choice and calibration
of a linear-characteristic spring, this means that the
second type of instrument will normally be the more
accurate. This is in accordance with the general rule that
null-type instruments are more accurate than deflection
types.
 
Is This Answer Correct ?    19 Yes 11 No
Sandy
 
Answer
# 2
A null type instrument as compared to deflection type
instrument has...which of the following.?
.(1)a higher accuracy(2)a lower reliability(3)a faster
response(4)all of the above?
 
Is This Answer Correct ?    5 Yes 0 No
Nupur
 
 
 
Answer
# 3
A null type instruments are more accurate than deflection types. 
Is This Answer Correct ?    4 Yes 1 No
Nupur
 
Answer
# 4
The pressure gauge is a good example of a deflection-type instrument, where the value of the quantity being measured is displayed in terms of the amount of movement of a pointer. An alternative type of pressure gauge is the dead-weight gauge which is a null-type instrument. Here, weights are put on top of the piston until the downward force balances the fluid pressure. Weights are added until the piston reaches a datum level, known as the null point. Pressure measurement is made in terms of the value of the weights needed to reach this null position.

The accuracy of these two instruments depends on different things. For the first one it depends on the linearity and calibration of the spring, whilst for the second it relies on the calibration of the weights. As calibration of weights is much easier than careful choice and calibration of a linear-characteristic spring, this means that the second type of instrument will normally be the more accurate. This is in accordance with the general rule that null-type instruments are more accurate than deflection types.

In terms of usage, the deflection-type instrument is clearly more convenient. It is far simpler to read the position of a pointer against a scale than to add and subtract weights until a null point is reached. A deflection-type instrument is therefore the one that would normally be used in the workplace. However, for calibration duties, the null-type instrument is preferable because of its superior accuracy. The extra effort required to use such an instrument is perfectly acceptable in this case because of the infrequent nature of calibration operations.
 
Is This Answer Correct ?    5 Yes 3 No
Jasmine
 
Answer
# 5
the null ins is gives the different between two
voltage/current......
the deflecting instrument is gives the value of the
measurand like voltage/current.....
 
Is This Answer Correct ?    15 Yes 20 No
Ramesh.a
 

 
 
 
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