Transducers - 1 - Dec 2014

Instrumentation Engg. (Semester 3)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) State True/False and justify-Bimetallic thermometer is unsuitable if the temperature changes are rapid.(5 marks) 1 (b) What do you mean by calibration? What is the need of calibration?(5 marks) 1 (c) The output of LVDT is connected to a 5V Voltmeter through an amplifier whose amplification factor is 250. An output of 2mV appears across the terminals of LVDT when the core moves through a distance of 0.5 mm. Calculate the sensitivity of LVDT.(5 marks) 1 (d) Write the criteria to be considered while selecting transducers.(5 marks) 1 (e) Explain Absolute humidity and relative humidity.(5 marks) 2 (a) Explain the flapper nozzle system and write its applications.(10 marks) 2 (b) Discuss the role of National Physical Laboratory in metrology. Write its advantages and disadvantages.(10 marks) 3 (a) Describe a rotational speed measurement system.(10 marks) 3 (b) Explain the following with respect to RTD -
i) Working principle
ii) Construction
iii) Materials used
iv) Self heating effect(10 marks)

Solve any two questions from Q4 (a), Q4 (b), Q4 (c).

4 (a) Explain the law of intermediate temperature and law of intermediate metals in case of thermocouple and give its significance.(10 marks) 4 (b) State different types of pyrometers. Explain with a neat sketch any one of them.(10 marks) 4 (c) Explain with a neat schematic diagram how the capacitance probe can be used for level measurement of non-conducting and conducting liquids.(10 marks) 5 (a) A thermistor has a resistance of 3980 Ω at the ice point (0°C) and 794 Ω at 50 °C. The resistance temperature relationship is given by R_T=a R₀ exp (b/T).
i) Calculate the constants a and b
ii) Calculate the range of resistance to be measured in case the temperature varies from 40°C and 100°C.(10 marks) 5 (b) Explain any five static characteristics of transducer with suitable example.(10 marks)

Write short notes on:

6 (a) Solid level detectors.(10 marks) 6 (b) Cold junction compensation in thermocouples.(10 marks)