Transducers - 1 - May 2015

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) Classify transducers with suitable example.(5 marks) 1 (b) Define
i) Accuracy
ii) Sensitivity(5 marks) 1 (c) Explain working principle of-
i) Piezo electric transducers
ii) Piezo resistive transducers(5 marks) 1 (d) Find seeback voltage for a thermocouple with proportionality constant of 40μV/°C if the junction temperatures are 40°C and 80°C.(5 marks) 2 (a) Draw and explain working of LVDT. What causes residual voltage to occur?(10 marks) 2 (b) A voltmeter having a sensitivity of 1000Ω/V reads 100V on its 150V scale when connected across an unknown resistor in series with milliammeter. When milliammeter reads 5 mA, calculate
i) Actual resistance of the unknown resistor.
ii) Error due to to loading effect of voltmeter.(10 marks) 3 (a) Explain any five static characteristics of transducer with suitable examples.(10 marks) 3 (b) What is the need of lead wire compensation? How it is to be done in RTD? What is self heating effect in RTD?(10 marks) 4 (a) For a certain thermistor β=3140 K and at 27°C is known to be 1050 Ω. The thermistor is used for temperature measurement and the resistance measured is as 2330 &Omega. Find the measured temperature.(10 marks) 4 (b) Draw set up and explain working of air purge method of level measurement.(10 marks) 5 (a) Explain radioactive type level detector in detail.(10 marks) 5 (b) A capacitive transducer uses two quartz diaphragm of area 750mm² separated by a distance of 3.5 mm. A pressure of 900 KN/m² when applied to top diaphragm produces a deflection of 0.6 mm. The capacitance is 370 pF when no pressure is applied to the diaphragm. Find the value of capacitance after the application of pressure 900 KN/m².(10 marks)

Write short notes (Any Two):

6 (a) Optical pyrometer.(10 marks) 6 (b) Rotary encoder.(10 marks) 6 (c) Types of error.(10 marks)