Oscilloscope

Protocol for measuring the electrical signals using an oscilloscope

Theory of the method:

Oscilloscope

Materials:

  • Oscilloscope
  • Rectifier: transformer, rectifier (diode), filter capacitor, switch
  • Coaxial cable

Procedure:

A. Callibrate the oscilloscope

  1. turn ON the oscilloscope (on the screen it is visible a bright spot)
  2. select one channel of the vertical block (ex: channel A)
  3. adjust the intensity of the spot; adjust the focus
  4. set the bright spot in the center of the screen ("positioning" knob)
  5. calibrate the signal on vertical axis - TIME/DIV knob
  6. calibrate the signal on horizontal axis - VOLTS/DIV knob
  7. set trigger: AUTOMATE

B. Measure the amplitude A and calculate the voltage V for AC

  1. select AC option in the vertical block
    1. obtain a sine wave:
      • connect the rectifier to the oscilloscope using the coaxial cable (BNC connector)
      • connect the rectifier to the power supply
    • settings: the circuit should not include the diode (terminal A and D connected)
      • TIME/DIV = 5 ms
      • VOLTS/DIV = 5 V
  2. measure the amplitude (number of divisions on the vertical axis)
  3. calculate the voltage for AC (ex: 5 V/square/5 divisions)

C. Measure the period T and calculate the frequency f for AC

  1. maintain the same settings
    1. measure the period (number of divisions on the horizontal axis/one cycle)
    2. calculate the frequency (ex: 5 ms/square/5 divisions)

D. Measure the amplitude A and calculate the voltage V for DC signal

    1. start from the previous settings
    2. transform AC in DC:
    • obtain the rectified current: include the diode (terminal B and D) = half-wave signal
    • select GND (ground) option in the vertical block; set the signal in the center of the screen
    • select DC option in the vertical block
    • filter the rectified current: include filter capacitor (same settings + close switch/ C) = filtered signal
    1. measure the amplitude
    2. calculate the voltage for DC

Useful links:

AC, DC and electrical signals: http://www.kpsec.freeuk.com/acdc.htm

Oscilloscope: http://www.kpsec.freeuk.com/cro.htm