Re: peaks in analog output signal

From: Johannes Schröck <johannes.schroeck_at_gmx.at> · Date: Wed, 23 Aug 2006 17:17:35 +0200

I tried what you suggested, calibration with all outputs disconnected, but
there is no improvement of the situation on the first output (D/A 0).
nevertheless, thanks for your advice, Alessandro.

during the calibration process this time I recognized the message:
"WARNING: caldac[8] pegged!"
what does this exactly mean? is it possible that this is somehow related to my problem?

Johannes

-------- Original-Nachricht --------
Datum: Wed, 23 Aug 2006 10:48:32 -0400
Von: Alessandro Toso <toso_at_aero.polimi.it>
An: ""Johannes Schröck"" <johannes.schroeck_at_gmx.at>
Betreff: Re: peaks in analog output signal

> Hi,
> 
> I have experienced something similar but I didn't investigate that  
> much just because I realized that calibrating the analog output board  
> with any kind of load (expecially capacitive I believe) gives you a  
> completely wrong calibratrion. So usually I make a calibration once a  
> week with all the output disonnected and the for the following  
> experiments I use the calibration data previously saved without the  
> need to disconnect everything again.
> I hope that can help you
> Bye
> 
> On Aug 23, 2006, at 10:16 AM, Johannes Schröck wrote:
> 
> >
> > yes, I swaped the signals, but the problem arises on the same  
> > output (D/A 0). Further investigations show that I also have little  
> > peaks on the second output, but just about +-0.05 V, while on the  
> > first output the peaks are almost +-0.2 V.
> >
> > -------- Original-Nachricht --------
> > Datum: Wed, 23 Aug 2006 08:54:26 -0400
> > Von: Mario Behn <behn_at_mirsl.ecs.umass.edu>
> > An: "\\"Johannes" Schröck" <johannes.schroeck_at_gmx.at>
> > Betreff: Re: peaks in analog output signal
> >
> >> Hi Johannes,
> >>
> >> have you tried to swap the signals?
> >>
> >> -- Mario 
> >> On Wed, 2006-08-23 at 09:13 +0200, "Johannes Schröck" wrote:
> >>> I use a PCI-DAS1200 board from Measurement Computing and I have a  
> >>> big
> >> trouble with analog output. This board provides two analog  
> >> outputs. While the
> >> second output works fine (D/A 1), the signal generated by the  
> >> first output
> >> (D/A 0) shows very disturbing peaks in the signal. The time distance
> >> between two peaks is equal to the sample rate. If I change the  
> >> sample rate also
> >> the time distance between the peaks changes in the same manner. I  
> >> really
> >> tried a lot to clarify this behaviour, but now I am on a point a  
> >> don't know
> >> what to do any more. This peaks affect measurement very hard.  
> >> While the
> >> signal from D/A 1 is quite smooth the signal from D/A 0 looks very  
> >> noisy.
> >>>
> >>> Does anybody observe similar behaviour befor? Is it possible,  
> >>> that this
> >> is a software problem? Or is this behaviour definitly a hardware  
> >> problem of
> >> the board?
> >>>
> >>> I use rtai 3.2, comedi 0.7.72, comedilib 0.7.22.
> >>>
> >>> Thanks for any help, Johannes
> >>>
> >>>
> >
> > -- 
> >
> >
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> 
> Alessandro Toso
> toso_at_aero.polimi.it
> 
> 

-- 

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