Q1) Two identical strain gages (1&2 shown in the figure below) are installed on a beam that supports a moment. Explain why two gages are used instead of one? Q2) The voice coil of a small speaker can be used as a velocity sensor. The coil has a diameter = pick any one from the table and has Number of turns=pick any one from the table of wire wrapped onto the core. The sensor exhibited a sensitivity of 50 mV/(m/s) over a range of frequencies. Estimate the magnetic field strength B in the gap occupied by the voice coil. 25 mm 30 mm 35 mm Diameter No. of Turns 40 mm 115 15 mm 120 80 90 110 (3) In oscillography recorders, there are two types of recorders: direct-writing and light-writing types. Which one is more suitable to record dynamic data and WHY? Q4) An RTDs fabricated from different materials exhibits a temperature coefficient of resistivity (y1 = pick any one from the table), Assume that y2 is negligible. If the resistance of the sensor = (pick any one from the table), Find the resistance at (-120). yl = 0.003/8 0.005/c 0.006/8 0.007/8 0.008/ 0.009/8 Resistance of the sensor 110 22 at oc 120 at 0c 130 at 02 902 at 08 80 Q2 at 0 100 2 at 0c (5) list three Mechanical quantities that can be measured using strain gage and two Mechanical quantities that can't be measured? (6) A thermocouple shows an e.m.f. of 8.00 mV with one of its junctions at 0 C and other at 100 C. If the 100 C junction is taken out of boiling water and placed in a glass of water having temperature same as room temperature, Calculate the e.m.f.registered on thermocouple: Assume the room temperature is any number listed in the table: 20 C 21 C 22 C 23 C 25 C 26 C 27 C (7) Mention TWO important sensors or transducers are commonly) used to measure the following quantities: Velocity: Temperature: Torque: Force : Tank level: Q8) For the beam-type load cell, Derive an expression to measure the load (P) using the attached strain gage on R4 connected using Wheatstone bridge as shown. Assume the following parameters are known: The cantilever parameters (h.b. E). Strain gage sensitivity Sg, Voltage source Vs and distance (x) Ry Force, pressure or displacement Strain gauge Structure Strain gauge Q9) Quick answers: Mention three disadvantages for "hospital" glass thermometers? Mention two differences between Type S and Type W thermocouples? What is the advantage of spiral thermometer over the straight strip type? What kind of load cells can be used to measure a low level loads? Why it is preferable to use a three lead wires instead of two in a strain gauge and bridge circuits? Q10) Derive the sensitivity expression for (strain gauge, C.C Wheatstone bridge, Non-inverting amplifier, and recorder) combination. Assume any parameters you need. Q11) Find Vo in the following op-amp (pick any values for R1 and R2 from the table). R2 w RI (K) R2 (K) R1 w 2 10 4 20 6 30 5V 8 40 Q12) R, is an RTD that has 100 and a = 0.00389 at O'C. Find R and Vo at 60'C. 400 w R3 Vo 5 V Q13) 100 velocity measurements are taken in a wind tunnel, the sample mean velocity is 5.126 m/s, the standard deviation of all the readings is 0.0690 m/s. We assume that the errors in the readings are purely random. Calculate the probability that the velocity of a random measurement is in the range 5.126 m/s