Analog scopes for noise measurements

Hello John,

You are right, won't work for pre-trigger stuff. We don't have that problem in ultrasound since there is nothing around before the transmit pulse, so I rarely have pre-trigger situations ;-)

Still, I am not too fond of even 1Gs/sec scopes. At least for repetive signals with some random and nasty noise in there the analog scopes often run circles around the DSOs. Unless you shell out really big bucks, of course.

Another typical situation is phase noise or EMI self-pollution. There you sit with a huge box over the scope and look for that wee thickening of a rising edge when something is turned on or off in the system. Not a chance with a regular upscale DSO.

Regards, Joerg

Hello John,

They are nice and I have to confess that I did find stuff like runt pulses with DSOs that an analog scope would never have shown.

This ain't fair. Then the analog scope has to get a FET probe as well.

I am using the Philips probe. That thing is tough. Once the mains plug adapter (its a Euro version) fell off and so I accidentally plugged it into the 230V lab rail. It took me about 10 minutes to find out why I couldn't zero the offset. Almost burned my hands on the PS. Plugged it into the 120V rail and bingo, it worked like a champ again.

But the old green glow has that real "engineer feel" to it. Until a CRT croaks and you receive the spare parts quote.

Regards, Joerg