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TA ZC232 (EC-2 Regular) Second Semester 2009-2010 Page 1 of 2

Birla Institute of Technology & Science, Pilani

Work-Integrated Learning Programmes Division

Second Semester 2009-2010

Comprehensive Examination(EC-2 Regular)

Course No. : TA ZC232

Course Title : ENGINEERING MEASUREMENTS

Nature of Exam : Open Book

Weightage : 60%Duration : 3 Hours

Date of Exam : 03/04/2010 (AN)

Note:1. Please follow all theInstructions to Candidates given on the cover page of the answer book.2. All parts of a question should be answered consecutively. Each answer should start from a fresh page.3. Mobile phones and computers of any kind should not be used inside the examination hall.4. Use of any unfair means will result in severe disciplinary action.Q.1. A first order measurement system with a time constant of = 0.1 sec is used to measure a

harmonically varying voltage. The voltage has a peak-to-peak amplitude of 6 volts and a

frequency of 5 Hz. Calculate the following (i) Frequency of the observed signal, (ii) The

steady state mean-to-peak amplitude value (iii) Phase of the observed signal in rad/secunit (iv) Time delay of the observed signal. [2 + 4 + 2 + 2 = 10]

Q.2. The radiation from a metal part is measured with a pyrometer which indicates atemperature of 300C. The actual part temperature is measured with a thermocouple

which indicates 315C. Both measurements have an uncertainty of 1C. From these

measurements, determine the emissivity of the metal part and its uncertainty. Alsodetermine the error in temperature. [4 + 4 + 2 = 10]

Q.3. The figure below shows a capacitor consisting of 2 metal plates each 400mm x 400mm,spaced 6 mm apart. The space between the metal plates is filled with a glass plate 5 mm

thick and a layer of paper 1mm thick. Relative permittivities of glass and paper are 8 and2 respectively. Find (i) Equivalent capacitance (ii) Electrical field strength in eachdielectric due to potential difference of 10 kV between the metal plates. The value of free

space permittivity is given as 0 = 8.85x10-12 F/m) [5 + 5 = 10]

1mm

Paper5mm

Glass

10 kV

No. of Pages = 2

No. of Questions = 6

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TA ZC232 (EC-2 Regular) Second Semester 2009-2010 Page 2 of 2

TA ZC232 (EC-2 Regular) Second Semester 2009-2010 Page 2

Q.4. An air-pressure signal at 5 atm and 50C is fed through a 1 mm-diameter line having alength of 0.8m and is connected to a transducer volume of 3 cm

3. Calculate the natural

frequency and damping ratio of this system. By how much will a pressure signal having afrequency one-half the natural frequency be attenuated? [10]

Q.5. Under zero-strain conditions the gage resistance of a bridge circuit is 120 . Calculate thegalvanometer current when = 350 m/m for a power supply voltage of 4 volt. Alsocalculate the voltage output for the bridge when used with high impedance detector. Given

that R2 = R3 = 110 and the galvanometer resistance is 70 . The gage factor is 1.8. Thebridge circuit is used to measure a strain-gage output. [10]

Q.6. Write the governing equation of a slug type heat-flux sensor. Use the same formula to findthe necessary heat flux to produce a rise in temperature of the sensor of 50C in 20sec.

Given that the slug is a copper cube 2.5mm on a side, U=0.1W/m2C, Sp. Heat of copper

is 398 J / kg C and density of copper is 8890 kg/m3. [1 + 9 = 10]

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