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'[EE] Scope Noise'
2005\02\02@110225 by Mauricio Jancic

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Hi,
       I'm observing that my scope has noise that is bothering me. If I
connect one chanel input to it's ground I think that I should see a 0V
signal, but instead I see a 22mV which seems to be a 1.8MHz added to an 4Mhz
signal (both sine waves) and also some random noise....

       How can I get rid of this? The problem stays with the scope either
grounded or not.

Regards,

PS: The scope is a DSO of 60MHz model INSTEK GDS-806S

Mauricio Jancic
Janso Desarrollos - Microchip Consultants Program Member
spam_OUTinfoTakeThisOuTspamjanso.com.ar
http://www.janso.com.ar
(54) 11 - 4542 - 3519

2005\02\02@121750 by Josh Koffman

face picon face
Are you connecting the channel to ground at the BNC input, or at the
end of a probe? Perhaps it's a probe issue.

Just a shot in the dark.

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Wed, 2 Feb 2005 13:02:29 -0300, Mauricio Jancic <.....jancicKILLspamspam@spam@ciudad.com.ar> wrote:
>         I'm observing that my scope has noise that is bothering me. If I
> connect one chanel input to it's ground I think that I should see a 0V
> signal, but instead I see a 22mV which seems to be a 1.8MHz added to an 4Mhz
> signal (both sine waves) and also some random noise....
>
>         How can I get rid of this? The problem stays with the scope either
> grounded or not.

2005\02\02@132840 by Andrew Warren

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Mauricio Jancic <piclistspamKILLspammit.edu> wrote:

> I'm observing that my scope has noise that is bothering me. If I
> connect one chanel input to it's ground I think that I should see
> a 0V signal, but instead I see a 22mV which seems to be a 1.8MHz
> added to an 4Mhz signal (both sine waves) and also some random
> noise....

Mauricio:

Nothing's wrong with your scope; you've simply built an antenna.  Are
there sources of 4 MHz and 1.8 MHz near your scope?  

-Andy

=== Andrew Warren -- .....aiwKILLspamspam.....cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
=== (but open to offers)
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

2005\02\02@134126 by Mauricio Jancic

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A: Yes, without the probe there is no signal.
B: Sources... Well, lets see: Monitor, CPU, Speakers, Another scope below
and a printer above, all that in 0.5 sq. meters... Oh, also de PS+ and an
ICD2, the circuit I'm debugging, soldering iron, Cable modem, 900Mhz wirelss
phone.... And my cup of cofee...:))

Regards,

{Original Message removed}

2005\02\02@162143 by Brent Brown

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> A: Yes, without the probe there is no signal.
> B: Sources... Well, lets see: Monitor, CPU, Speakers, Another scope below
> and a printer above, all that in 0.5 sq. meters... Oh, also de PS+ and an
> ICD2, the circuit I'm debugging, soldering iron, Cable modem, 900Mhz wirelss
> phone.... And my cup of cofee...:))

Try moving the cofee :-)

--
Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  EraseMEbrent.brownspam_OUTspamTakeThisOuTclear.net.nz


2005\02\02@164108 by Mike Hord

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> > A: Yes, without the probe there is no signal.
> > B: Sources... Well, lets see: Monitor, CPU, Speakers, Another scope below
> > and a printer above, all that in 0.5 sq. meters... Oh, also de PS+ and an
> > ICD2, the circuit I'm debugging, soldering iron, Cable modem, 900Mhz wirelss
> > phone.... And my cup of cofee...:))
>
> Try moving the cofee :-)

Or switching to decaf...

Mike H.

2005\02\02@164725 by Andrew Warren

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Mauricio Jancic <piclistspamspam_OUTmit.edu> wrote:

> B: Sources... Well, lets see: Monitor, CPU, Speakers, Another
> scope below and a printer above, all that in 0.5 sq. meters... Oh,
> also de PS+ and an ICD2, the circuit I'm debugging, soldering iron,
> Cable modem, 900Mhz wirelss phone.... And my cup of cofee...:))

   Perfectly normal, then.  I sometimes intentionally make an
   antenna that way in order to find RF sources.

   -Andy

=== Andrew Warren -- @spam@aiwKILLspamspamcypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
=== (but open to offers)
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

2005\02\03@135024 by Peter L. Peres

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On Wed, 2 Feb 2005, Mauricio Jancic wrote:

> A: Yes, without the probe there is no signal.
> B: Sources... Well, lets see: Monitor, CPU, Speakers, Another scope below
> and a printer above, all that in 0.5 sq. meters... Oh, also de PS+ and an
> ICD2, the circuit I'm debugging, soldering iron, Cable modem, 900Mhz wirelss
> phone.... And my cup of cofee...:))

Turn off each device and see what helps. Start with the coffee ;-)

Peter

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