2 May
2010
2 May
'10
7:34 a.m.
On Sat, 1 May 2010, Chris M wrote:
Date: Sat, 1 May 2010 12:36:59 -0700 (PDT)
From: Chris M <chrism3667 at yahoo.com>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: cctech at classiccmp.org
Subject: new acquisitions
I happen to have a probe I picked up from somewhere in my garbage garage.
The inputs on these 2 scopes require 1Mohm wit either 22pF or 47 pF of
capacitance. What does this mean? There's simply a capacitor between the
coax? The resistance part is strait forward presumably. If that's the case,
then you can just jury rig an acceptable probe, no?
It means the input of the scope has 1 M resistance in parallel with 22 or
47 pF of capacitance. This means that a 10-1 probe for example would need to
be adjustable to accomodate this input impedance. Probes are usually marked
with what input capacitance range they can drive (The 1M resistance is
standard for all high impedance probes)
Peter Wallace