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From: "Tom Del Rosso"
Subject: Re: logic probe not handling input from test leads
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
NNTP-Posting-Date: Tue, 05 Nov 2002 19:14:14 GMT
Organization: AT&T Worldnet
Date: Tue, 05 Nov 2002 19:14:14 GMT
"Duane Fields" wrote in
> [......]. The circuit is designed to dimly light the
> LED to indicate an "open" connection, one not grounded or at High.
> seems to work until I plug in my test lead, which immediately drops
> off completely. It still indicates pulse or high values properly - but
> can never be indicated.
The long lead is probably picking up EMI. The probe is probably meant
to be like the probes of most commercial logic probes - a short needle.
Try a short wire and see what happens. What happens when you simply
unplug the test leads?
If you can fit the board into a plastic box that a toothbrush comes in,
or the case of a fat marker pen, you can have a needle (maybe taken from
a drawing compass) stick out one end. Then you'd have a nice one-piece
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