Scope Probe Ground Spring

If you are serious about measuring high speed signals or try to do measure sensitive signals around a noisy environment e.g. switch mode supplies/motors, you really should use a ground spring. That long ground strap that comes with the scope probe can pick up magnetically coupled noise and taint your measurements.  The larger the loop area is, the more noise you are going to potentially pick up.

See Understanding, Measuring, and Reducing Output Voltage Ripple

Here is a quick and dirty way of making a ground spring if you need one.

Better still, you can unscretch the spring to accommodate the probe.

Here is a noise measurement on a 5V rail with the long ground lead.

Here is the same measurement with the ground spring.