MOTM

You can always put a series resistor in the plug body if you're really
concerned.  Most scopes have a 1M input impedance.  The method
I described is really a X1 probe with some pF's of capacitance/ft due to the
coax.  For audio frequencies it probably isn't going too matter much.
Put a 9M resistor in series in the plug and you have a X10 probe.

Note many Tek scopes aren't going to recognize it as a X10 probe
due to the autosense mentioned earlier.

(If you really want to compensate it, you can put a little (variable)
cap inside the plug body as well.)

--- On Thu, 1/29/09, Richard Brewster <pugix@...> wrote:
From: Richard Brewster <pugix@...>
Subject: Re: [motm] Scope question
To: lists@...
Cc: motm@yahoogroups.com
Date: Thursday, January 29, 2009, 4:37 PM










    
            I've been getting by with the simple approach of just clipping a 10x 

probe to a 1/4-inch plug without its housing.  I like the idea of 

preserving the impedance features of the probe, rather than just 

connecting directly to the scope BNC input.



Richard Brewster

http://www.pugix. com



Adam Schabtach wrote:

> Aside from all of the suggestions that have been aired for connecting 

> a 1/4"audio plug to a BNC connector, there's another solution that's 

> somewhat more flexible: buy a scope probe with a clip-on probe 

> cover, then clip it to a 1/4" plug with its shell removed. This will 

> give you hands-free operation with both the 1/4" plug and anything 

> else you need to look at with a scope.

>  

> Here's a random example of what I'm talking about:

> http://www.testpath .com/Items/ Passive-Oscillos cope-Probe- 15MHz-X1- 110-564.htm

> (No, I've never used that particular probe. It was just the first 

> example I found.)

>  

> --Adam

>

>     ------------ --------- --------- --------- --------- --------- -

>     *From:* motm@yahoogroups. com [mailto:motm@yahoogroups. com] *On

>     Behalf Of *jneilnyc

>     *Sent:* Wednesday, January 28, 2009 8:25 PM

>     *To:* motm@yahoogroups. com

>     *Subject:* [motm] Scope question

>

>

>     I finally sat down tonight at got my Tektronix to give me some

>     waveform views of one of my oscillators. There was more than a little

>     trial-and-error at first, but once I got in the ballpark I was able to

>     zero in on clear, static waveforms that changed shape in predictable

>     and expected ways, which was immensely satisfying (and will no doubt

>     impress my musical buddies, for whom a MOTM cabinet is already like

>     seeing something out of Close Encounters - this now adds that last mad

>     scientist touch).

>

>     And I got the onboard frequency counter working, which is a nice plus.

>

>     All this was done using a rather painful method whereby I clipped the

>     ground to one exposed terminal on the end of a phone cable and touched

>     the probe to the other. While this worked, it was not at all easy to

>     do one-handed, and clearly not a long-term methodology. What I really

>     want is to make this kind of connection permanent, ie just have some

>     sort of probe terminating in a phone plug that I can tap into any jack

>     without worrying about fiddly connections. Does such a thing exist,

>     either ready-to-use or in some combination of probes+adaptors?

>

>     What do people who know what they're doing do? (he said, and not for

>     the first time...)

>

>     Thanks!

>     JN

>

>