How to operate the oscilloscope

To operate an oscilloscope the user must learn how to ground the oscilloscope and set its controls. The user must also learn how to calibrate the oscilloscope as well as connect and compensate its probes.

To ground the oscilloscope means connecting it to an electrically neutral reference point. This can be achieved by connecting the three-pronged power cord of the oscilloscope into an outlet grounded to earth ground.

Grounding the oscilloscope is vital for the safety of the user. Once a high voltage comes in contact with an ungrounded oscilloscope’s case, any part of the case can give the user a shock. But with a grounded oscilloscope, the current passes through the grounding path and straight to the earth ground rather than through the user to the earth ground.

After the oscilloscope has been properly plugged in, the user must look for the input connectors, where the probes will be attached. Most oscilloscopes feature at least two input channels, with each channel displaying a waveform on the screen. Meanwhile, multiple channels are very useful for comparing waveforms.

Some oscilloscopes come with DEFAULT and/or AUTOSET buttons, which can be used to set up the controls in just a single step to accommodate a signal. If the oscilloscope does not offer this capability, the user can set the controls to standard positions prior to taking measurements.

To set the oscilloscope to standard positions, the user must first adjust the oscilloscope to display channel 1, then set the vertical volts/division scale and set the controls to mid-range positions. The next step is to turn-off the oscilloscope’s variable volts/division as well as all of its magnification settings. Then the user should set the channel 1 input coupling to DC, the trigger mode to auto and the trigger source to channel 1. After which, the trigger hold off function of the oscilloscope must be set to minimum or off, while the horizontal time/division and position controls must be set to mid-range positions. Finally, the channel 1 volts/division must be adjusted to enable the signal to occupy as much of the 10 vertical divisions without signal distortion or clipping.

Aside from proper oscilloscope setup, calibrating the device is also recommended to achieve accurate measurements. Calibrating the oscilloscope is needed if its ambient temperature has changed to over 5°C (9°F) since its last self-calibration. This can be initiated as the “Signal Path Compensation” from the oscilloscope menu.

The next step is to connect a probe to the oscilloscope. A probe ensures the integrity of the signal being measured by enabling it to access all of the performance and power of the oscilloscope.

Prior to using a passive probe, it must first be compensated in order to balance its electrical properties. A poorly adjusted probe usually yields less accurate measurements.

Basic oscilloscope operation

In general electronics use, when measuring AC voltage signals, what do the two axes (horizontal and vertical) of the oscilloscope screen represent?
  The core of an analog oscilloscope is a special type of vacuum tube known as a Cathode Ray Tube, or CRT. While similar in function to the CRT used in televisions, oscilloscope display tubes are specially built for the purpose of serving an a measuring instrument.
Explain how a CRT functions. What goes on inside the tube to produce waveform displays on the screen?
   
When the vertical ("Y") axis of an oscilloscope is shorted, the result should be a straight line in the middle of the screen:
   
A technician prepares to use an oscilloscope to display an AC voltage signal. After turning the oscilloscope on and connecting the Y input probe to the signal source test points, this display appears:
   
A technician prepares to use an oscilloscope to display an AC voltage signal. After turning the oscilloscope on and connecting the Y input probe to the signal source test points, this display appears:
   
A technician prepares to use an oscilloscope to display an AC voltage signal. After turning the oscilloscope on and connecting the Y input probe to the signal source test points, this display appears:
   
Assuming the vertical sensitivity control is set to 2 volts per division, and the timebase control is set to 10 μs per division, calculate the amplitude of this ßawtooth" wave (in volts peak and volts peak-to-peak) as well as its frequency.