The other question I have is related to grounding. My house currently has 1950s vintage US wiring, i.e. an ungrounded system. I only have phase and neutral running around. I'm talking to an electrician about how much it'd hurt to get everything grounded anyway, but in the meantime, how much will it suck if I use the scope without an earth connection? Am I to expect additional noise, damage to the scope, certain death?
Thanks in advance!
The probe questions have already been adequately covered,so I'll confine my comments to this paet of your question.
Although it's a bummer that you don't have an Earth connection on your power points,it isn't the end of the world.
People have used Oscilloscopes in such situations in the past without injury.
If the 120Vac wiring inside your 'scope
does not have a fault condition that connects the Active (HOT)
conductor to the metalwork of the 'scope you are safe under normal circumstances.
If you had such a fault,& touched both the Oscilloscope & a nearby Earthed object,such as a tap,sink,etc,you would get a dangerous shock.
Note:Even if there is no connection between Neutral & Earth in your house cabling,that doesn't mean that there is not one somewhere else---there almost certainly will be.
MEGA-NOTE!!!!:-If you decided to measure the 120vac out of your power socket,with your 'scope,you have a 50:50 chance that you will create the fault condition referred to above.
Dont do it!!!In both of the situations referred to above,where there is a connection between Active & the 'scope metalwork,the result in the more normal situation where the metalwork
is earthed via the power point,would be a short circuit between Active & Neutral,large "bang" & the associated house fuse or circuit breaker will blow or trip.
This is the reasoning behind the concept of providing a "protective earth".
Any fault condition connecting the metalwork of an appliance & the Mains Active line will result in an overload on that line,& not an electric shock to the user.
There is no fuse in the Earth cabling,so the metalwork of protected device cannot rise above Earth potential.