Process Control and Instrumentation MCQs

Question 1

For increased speed of response of an expansion pressure spring thermometer, the thermometer bulb should have a

Accepted Answer

All of the above

Answer

Large area but small mass

Answer

High thermal conductivity

Answer

Small specific heat

Question 2

Conversion formula for converting amplitude ratio (AR) into decibels is

Accepted Answer

Decibel = 20 log 10 (AR)

Answer

Decibel = 20 log e (AR)

Answer

Decibel = 20 log 10 (AR) 0.5

Answer

Decibel = 20 log e (AR) 0.5

Question 3

Which of the following is an undesirable dynamic characteristic of an instrument?

Accepted Answer

Time lag

Answer

Reproducibility

Answer

Dead zone

Answer

Static error

Question 4

Mass spectrometer is used for the composition analysis of

Accepted Answer

Isotopes

Answer

Alloys

Answer

Solids

Answer

None of these

Question 5

On-off control which is a special case of proportional control, has a band width of about __________ percent.

Accepted Answer

0

Answer

100

Answer

75

Answer

25

Question 6

Pick out the wrong statement.

Accepted Answer

Transfer lag decreases as the number of stages decreases

Answer

There is no transfer lag for a single first order system

Answer

Stirred tank with a water jacket exemplifies an interacting system

Answer

Transfer lag is a characteristics of all higher order systems (other than first order systems)

Question 7

For a feed back control system to be stable, the

Accepted Answer

Poles of the closed loop transfer function should lie in the left half of the complex plane

Answer

Roots of the characteristic equation should be real

Answer

Bode plots of the corresponding open loop transfer function should monotoni-cally decrease

Answer

Poles of the closed loop transfer function should lie in the right half of the complex plane

Question 8

Very low pressure is expressed in microns(μ), which is equal to __________ mm of Hg coloumn (absolute) at 0°C.

Accepted Answer

0.001

Answer

0.0001

Answer

0.01

Answer

0.1

Question 9

Thermistors are made of

Accepted Answer

Metal oxides

Answer

Ultra pure metals

Answer

Iron-copper alloys

Answer

Nickel-chromium alloys