What Causes the Waveforms When Holding an Oscilloscope Probe?

[General_Sax]

Homework Statement

Disconnect the oscilloscope from the circuit and hold the red lead of one of the oscilloscope inputs in your hand...

What are the sources of the waveforms observed in the above step?

What do the amplitudes of the observed waveforms depend on?

Homework Equations

xx

The Attempt at a Solution

I'm really not sure at all, and my TA hasn't responded to my e-mail.

I think the sources of the waveform could be

a) my hand

b) electric fields from surrounding equipment


And I think the waveforms can depend on

a) electric field of my body

b) proximity to equipment running


Thanks for any help. I'm really lost and I need to finish this lab report tomarrow.

 

[madmike159]

The oscilloscope measures voltage, which means there must be a current. Any changing magnetic fields in the room will induce a small current into the lead which is then measured. These magnetic fields can be caused by things like AC in the mains wiring. When you hold the metal you are helping some of the induced current go to ground so the wave probably gets smaller.

 

[berkeman]

Homework Statement

Disconnect the oscilloscope from the circuit and hold the red lead of one of the oscilloscope inputs in your hand...

What are the sources of the waveforms observed in the above step?

What do the amplitudes of the observed waveforms depend on?

Homework Equations

xx

The Attempt at a Solution

I'm really not sure at all, and my TA hasn't responded to my e-mail.

I think the sources of the waveform could be

a) my hand

b) electric fields from surrounding equipment


And I think the waveforms can depend on

a) electric field of my body

b) proximity to equipment running


Thanks for any help. I'm really lost and I need to finish this lab report tomarrow.

My reply may be too late for your report, but the main component that you will see on an oscilloscope if you hold the probe tip (exposed metal tip) in your hand will be 50/60Hz AC Mains noise. The noise is capacitively coupled to your body from nearby AC Mains circuits.