Proper grounding is an important step when setting up to take measurements or work on a circuit. Properly grounding the oscilloscope protects you from a hazardous shock and grounding yourself protects your circuits from damage.
Ground the Oscilloscope
Grounding the oscilloscope is necessary for safety. If a high voltage contacts the case of an ungrounded oscilloscope, any part of the case, including knobs that appear insulated, it can give you a shock. However, with a properly grounded oscilloscope, the current travels through the grounding path to earth ground rather than through you to earth ground.
To ground the oscilloscope means to connect it to an electrically neutral reference point (such as earth ground). Ground your oscilloscope by plugging its three-pronged power cord into an outlet grounded to earth ground.
Grounding is also necessary for taking accurate measurements with your oscilloscope. The oscilloscope needs to share the same ground as any circuits you are testing.
Some oscilloscopes do not require the separate connection to earth ground. These oscilloscopes have insulated cases and controls, which keeps any possible shock hazard away from the user.
If you are working with integrated circuits (ICs), you also need to ground yourself. Integrated circuits have tiny conduction paths that can be damaged by static electricity that builds up on your body. You can ruin an expensive IC simply by walking across a carpet or taking off a sweater and then touching the leads of the IC. To solve this problem, wear a grounding strap (see Figure 1). This strap safely sends static charges on your body to earth ground.
Typical Wrist Type Grounding Strap