Birla Institute of Technology (BIT Mesra) 2007 INSTRUMENTATION & CONTROL - Question Paper

Birla Institute of Technology & Science, Pilani

Distance Learning Programmes Division

Second Semester 2006-2007

Mid-Semester Test (EC-1 Regular)



Course No. : ET ZC341

Course Title : INSTRUMENTATION & CONTROL

No. of Pages = 1

No. of ques. = six
Nature of examination : Closed Book

Weightage : 40%

Duration : two Hours

Date of examination : 03/02/2007 (AN)

Note:

1. Please follow all the Instructions to Candidates provided on the cover page of the ans book.

2. All parts of a ques. should be answered consecutively. every ans should begin from a fresh page.

3. Mobile phones and computers of any type should not be brought inside the exam hall.

4. Use of any unfair means will outcome in severe disciplinary action.



Q.1. The resistance of a thermistor at temperature q K is provided by . provided that the resistance at ice point (q = 273.15 K) is 9.00 kW and the resistance at the steam point is 0.50 kW, obtain the resistance at 25°C. [5]



Q.2. What is the percentage non-linearity fault with a potentiometer of resistance 550W which outcomes from there being a load of resistance 10 kW when it is at a displacement which is half its maximum slider travel and the supply voltage is 10V dc? [5]



Q.3. A force sensor has a mass of 0.5 kg, stiffness of 2.35 x 102 N/m and a damping constant of 6.0 N s/m.



(a) compute the steady-state sensitivity, natural frequency and damping ratio for the sensor.

(b) compute the displacement of the sensor for a steady input force of three N.

(c) If the input force is suddenly increased from two to three N, derive an expression for the resulting displacement of the sensor. [3 + two + three = 7]



Q.4. A platinum resistance thermometer has a resistance at 0ºC of 123W and forms 1 arm of a Wheatstone bridge. At this temperature the bridge is balanced with every of the other arms also being 123 W. The temperature coefficient of resistance of the platinum is 0.0039/ºC. What will be the output voltage for change in temperature of 30ºC if the instrument used to measure it can be presumed to have infinite resistance and the supply voltage, with negligible internal resistance, for the bridge is 9.0 V dc? [7]



Q.5. A variable reluctance sensor consists of a core, variable air gap and an armature. The core is a steel rod of diameter one cm, relative permeability 100 bent to form a semi circle of diameter four cm. A coil of 550 turns is wound onto the core. The armature is a steel plate of thickness 0.6 cm and relative permeability 100. Assuming the relative permeability of air = 1.0 and the permeability of free space = 4p x 10-7 H/m, compute the inductance of the sensor for air gaps of one mm and three mm. [8]



Q.6. discuss the subsequent with the help of suitable examples: [2 x four = 8]



(a) Hysteresis

(b) Accuracy and Precision

(c) Range and Span

(d) Repeatability and Reproducibility

Earning:   Approval pending.