7001
FOURTH SEMESTER B.TECH DEGREE MODEL EXAMINATION, MARCH 2018
Course Code: EE 208
Course Name: MEASUREMENTS AND INSTRUMENTATION (EE)
ANSWER KEY

Adjustable small weight is used which Two ரவா aprings are used which exert
produces the controlling torque. controlling torque.

Controlling torque can be varied. Controlling torque is fixed

— 4

Simple. rigid but costlier compared to
gravity control.

Very popularty used in most of the
instruments.

Measurement of high resistance using loss of charge method
include leakage resistance of C

The circuit consists high insulation resistance R to be measured alongwith capacitor of
known value C shunted with electrostatic voltmeter and leakage resistance R,.

Initially, capacitor C is charged to suitable voltage say | by moving switch to position
1. Then switch is moved to position 2. The capacitor starts discharging through parallel
combination of R and R,. At certain instant t voltage across capacitor C i.e. V2 is measured
using electrostatic voltmeter. Thus in time t, voltage across capacitor drops down from V,
to V2. Let the equivalent resistance through which C discharges be denoted by R’ where
२ || ಣೃ.

The expression for current any instant 6 is given by,

dq dv
i= --वाः = - <वा न @)
But a Pond ನೇಲ ‏موس‎ across R’ => x ‏۔۔۔‎ (3)
R R
Comparing equations (2) and (3), we can write,
37 dv dv dt

ge a © आए! 2