APPLIED & ELECTRONICS INSTRUMENTATION

APPLIED & ELECTRONICS INSTRUMENTATION
SEM-V, 2011-12
B.TECH EXAMINATION
UTTARAKHAND TECHNICAL UNIVERSITY
utu question paper

Time: 3 Hours

Total Marks: 100

Attempt any four parts:

1. Explain the following terms with suitable example and graph:
   (a) Accuracy and Precision
   (b) Dead time and Dead zone
   (c) Sensor and Actuator
2. What are the input test signals and give the dynamic characteristics for the first order system with suitable example?
3. Why Sensitivity and Linearity are the two conflicting requirements in a resistive potentiometer?
4. Two plates of parallel plate capacitive transducer are 30 mm apart and the space is filled with two different dielectric materials, one material is 1 cm thick with dielectric constant of 10, if the capacitive transducer were to be made with single dielectric material, what is the dielectric constant of that material?
5. A strain gauge has a gauge factor of 4. If the strain gauge is attached to a metal bar that stretches from 0.25 to 0.255 mm when strained, what is the percentage change in resistance? If the unstrained value of gauge factor is 120Ω, what is the resistance value of gauge factor after application of strain?
6. Design the Wheatstone bridge arrangement employed for the measurement of Strain for the Quarter Bridge, Half Bridge and Full Bridge with respective sensitivity.

Attempt any four parts:

1. Describe the Load cell with constructional feature of Ring type load cell and show how their output signals enable further processing for indication.
2. Describe the method of measurement of differential pressure using inductive type transducer and differentiate between Absolute, Gauge and Differential pressure referred in this case.
3. A resistive Transducer with a resistance of 5 KΩ and a shaft distance is 5 inch is used in arrangement as shown in figure. Potentiometer R₃-R₄ is also 5K and V is 5V. The initial position to be used as reference point is such that R₁=R₂. At the start of the test, Potentiometer R₃- R₄ is adjusted so that the bridge is balanced (V_o=0). Assuming that the object being monitored moves a max. Resistance of 0.5 inch toward A. What will be the new value of V_o?
   
   
   
4. An LVDT has an output of 6V when the displacement is 0.4 x 10^-3 mm. Determine the sensitivity of this instrument in V/mm. A 10V voltmeter with 100 scale divisions is used to read the output. Two tenth of a division can be estimated with ease. Determine Resolution of the voltmeter.
   The above arrangement is used in pressure transducer for measuring the deflection of diaphragm. The diaphragm is deflected through 0.5 x 10^-3 mm by a pressure of 1000 N/m². Determine the sensitivity and resolution of this instrument?
5. Explain the principle working of thermistor, its relation with temperature and its characteristics.
6. The EMF of an Iron-Constantan thermocouple is to be measured by the potentiometer shown in fig. a potential difference of 1.0186 V is applied over point A&B. The current through the resistor is 2mA and the range of temp. Measurement is 250- 850^o C. Calculate R₁, R₂ and R₃ for ambient temp 20^o C. The EMF of iron-constantan couple with reference junction at 0^o C is 1.019 mV at 20^o C, 13.553 mV at 250^o C and 48.176 mV at 850^o C.
   

Attempt any two parts:

1. (a) Which one method is mostly preferred for vibration measurement and why? And explain its working with proper diagram and its magnitude and phasor graph?
   (b) Explain the piezoelectric Accelerometer with its neat and clean Schematic diagram and its features.
2. What is the basic function of the Tachometer and describe the working principle of A.C Tachometer and its advantages?
3. What do you understand by Shaft-Torque? Explain the principle working of the Strain Gauge Torque meter with its functional diagram.

Attempt any two parts:

1. (a) What is the basic concept of the Earth Ground and how can we reduce the noise introduced by Ground loops and Inductive coupling?
   (b) A measurement system uses a resistance strain gauge for measurement of pressure. The strain gauge has an unstrained resistance of 120Ω and is connected in one arms of the bridge. The other three arms of the bridge have each a resistance of 120Ω the temperature is 300⁰ K the bandwidth is 100 KHz. The output of the bridge is a voltage signal.
   (i) When a pressure of 7000 kN/m² is applied the output voltage is 0.12 mV. Find the ratio of the output (signal) voltage to the noise voltage generated by the resistor. Also comment on the effect of noise over signal and its interference.
   (ii) Find the ratio of the output signal voltage to noise voltage if the pressure is 7 kN/m². Also comment on the resulting effect of noise and interference?
2. (a) In order to measure noise figure of an amplifier, a noise voltage that is 10% of the signal voltage that is 10% of the signal voltage is applied at the input of the amplifier. The noise voltage at the output of the amplifier is 20% of the signal voltage. Calculate the noise figure of the amplifier.
   (b) What is the difference between Radio telemetry and radio communication and explain the FM/FM ratio telemetry scheme?
3. How can we measure the liquid pressure placed in a beaker by PWM telemetry scheme? Explain with its functional block diagram and waveforms.

Attempt any two parts:

1. (a) Describe the functional behavior of chopper in D.C. Electronic Voltmeter with its working diagram.
   (b) Twenty one data channels, with sub carrier center frequency ranging from 400 Hz to 165 KHz have been designated for telemetry use. All have a frequency deviation of ±7.5%. Assuming modulation index of 5, obtain intelligence bandwidth of channel first for a center frequency of 70 KHz. Assuming that frequency division have been used.
2. What factors discriminate the Electronic Wattmeter from dynamometer type Wattmeter and explain the working of Analog Electronic Wattmeter with schematic diagram.
3. (a) Describe the working principle of the Integrating type Digital voltmeter with suitable diagram and Waveform Representation.
   (b) What method should be preferred for the measurement of frequency? Describe it with proper functional diagram.

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