Re: Oscilloscope, How TO?

From: Asimov (Asimov_at_-removethis-bbs.juxtaposition.dynip.com)
Date: 07/31/04 

Date: Friday, 30 Jul 2004 23:11:32 -500

"id" bravely wrote to "All" (30 Jul 04 20:02:10)
 --- on the heady topic of "Re: Oscilloscope, How TO?"

 id> From: "id" <taurus@nowhere.com>

 id> Don't isolate the scope from AC power ground. The scope frame and
 id> ground points will go to the potential of the probe ground which could
 id> be harmful to
 id> the health of you and your scope. Most 2 channel scopes have channel
 id> A+ channel B (A+B) input selection. If you select that and invert A,
 id> the scope will display the difference between the 2 channels. If there
 id> is a large DC component, select AC inputs to measure low level ripple.
 id> Be sure to connect the grounds of both probes to the frame or AC ground
 id> of the device being measured.

I have an old scope that has differential inputs on each channel.
Normally the inverting input is grounded with a strap and the
non-inverting connects to the probe. Would this work in your opinion?

BTW on the same old tube scope when set to display both channels the
trace becomes distorted, and the A channel seems to bleed into the B
channel. Each channel works perfectly on its own so I was thinking the
problem was in the chopper, perhaps a bad switch in the matrix?

The chopper seems to be housed in a small square box which feeds into
the vertical output tube driving the crt. The switching matrix seems
to be made up of what may be early fets or transistors, not sure
which, since it is very difficult to take a peek due to construction.
The scope is an Analab. (what an anal brand name, who thinks these up!)

 A*s*i*m*o*v

... High voltage can give a dangerously uncomfortable discharge.

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