Electronic Instrumentation

Electronic Instrumentation Test 1-2007

Part A:

1. Explain with a detailed diagram the measurement of frequency   (10 marks)

2. Explain the successive approximation method of analog to digital conversion

     used in digital voltmeters with detailed diagram                          (10 marks)

Part B:

3(a) Explain with diagram and waveform the Integrating type DVM to convert

        Voltage to frequency.                                                                   (8 marks)

(b) An integrator contains a 100 Kilo Ohm and 1 microfarad capacitor. If the

     voltage applied to the integrator output is 1 Volt, what voltage will be present

     at the output of the integrator after 1 second? Now, if a reference voltage

     applied to the integrator at time t₁ is 5 volts, what is the time interval

     of t₂.                                                                                                (2 marks)

4. Figure shows a simple series circuit of R1 and R2 connected to a 100 Volt

     DC source. If the voltage across R2 is to be measured by voltmeter

      having

        (a) a sensitivity of 1000 ohms/volt and

        (b) a sensitivity of 20,000ohms/volt,

     find which voltmeter will read the accurate value of voltage across R2.

     Both meters are used on 50 Volt range.                                          (10 marks).

Part C:

5. Convert the basic D’Arsonval movement with an internal resistance

    of 50 Ohms and a full scale deflection current of 2 milliamps into a

    multi-range DC voltmeter with voltage ranges of 0-10 volts and 0-50 volts

                                                                                                               (5 marks)

6. Explain Gross error, Systematic error, Absolute error and

   Relative error.                                                                                    (5 marks)

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Electronic Instrumentation Test 2-2007

Part A:

1(a) Explain the different CRT features.                                              (5 marks)

(b) Explain the different types of sweeps.                                            (5 marks)

2 Explain the operation of triggered sweep CRO with appropriate

   diagram.                                                                                         (10 marks)

Part B:

3. Explain the different parts of a typical CRT connection with

    appropriate diagram.                                                                     (10 marks)

4. Explain with diagram the electronic switch used in dual trace

    oscilloscope.                                                                                (10 marks)

Part C:

5. Explain briefly with diagram the principle of operation of the

    variable persistence storage CRT.                                               (5 marks)

6. Draw the circuit diagram of the sampling oscilloscope system

    and explain briefly with waveforms.                                          (5 marks)

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Electronic Instrumentation Test 3-2007

Part A:                  

1(a) Arrive at the Thevanin’s equivalent circuit for slightly unbalanced

       Wheatstone’s bridge.                                                                         (5 marks)

(b) An unbalanced Wheatstone’s bridge is as shown. Calculate the

     current through the galvanometer.                                                      (5 marks)

2(a) How is unknown frequency measured using a bridge? Explain

       with appropriate expression.                                                          (5 marks)

  (b) Explain the method of eliminating stray capacitances in a bridge. (5 marks)

Part B:

3. Explain the working of the Linear Variable Differential Transducer. (10 marks)

4. What is the working principle of a strain gauge? Derive the expression

     for the gauge factor of a strain gauge.                                                (10 marks)

Part C:

5. With a neat diagram and waveform explain how the stored information

     is recovered in a digital storage oscilloscope.                                     (5 marks)

6. Explain the following:

       (i) Interpolation

       (ii) Sampling rate and bandwidth.                                                      (5 marks)