Hi Jeff,

You can use a 1,000 Ohm resistor to test input pins. Just tie one end to +5 Volts and use the other end to touch whatever you want. This will prevent any damage to your device under test.

You can also use the same method for ground. Just tie one side of the resistor to ground and touch whatever you want.

This way you protect your devices.

Good Luck.

Charles Bannister