o-scope - test-drb@ccmp.vtda.org

6 May 2001

From: Jim Strickland &lt;jim(a)calico.litterbox.com&gt;
...
 So I'm a 'scope newbie, does the probe
impedance (13 pf) have to match the
...
 rating on the jack on the scope (47 pf) for the waves
coming out of the
calibration jack to be properly square?  And if so, does anyone have a source
...
 for probes that work with ancient scopes like this?

No not required to match.  That specification is the capacitance
presented
across the input jack along with the scopes input resistance (usually
1megohm).
Most scope probes have an adjustment to compensate for this and therefor
it's not a problem.

...
 Other than the waveform distortion (at worst the square
waves wind up looking
...
 like shark teeth, and at best they're a bit sloped
on the leading and top
...
 edges) the scope seems to work fine as far as I can
tell. 

Probe compensation is off or the amplifier (vertical) are misadjusted
internally.

A square wave on that series should look square.

Allison