Time drift between 2 different data streams

Fri Mar 25 18:43:52 UTC 2011

thank you for the reply!!

about the first question,
the systems are connnectend by parallel cable.

About the experiment, it s structured as follow
stimulus (sent by the simulator) -> vocal response given by the subject
using a mic connected with a SRBox ->Feedback (and so on with the other 99
loops)

About what e-prime is doing
Yes, E-prime merely logging voice-key data. Every stimuli are sent from a
driving simulator.
The simulator send a signal (via parallel port) at the start, and another at
the end, of the experiment. With two "while loops" we control the start and
the and of the experiment. E-prime exits from "while loop" when it reads the
signal sent from the simulator. we know the time when the simulator send the
signal and the time when E-prime reads this signal. So I can calculate the
time difference between the simultator and the PC.The difference at the
start is less than the difference at the end. But I don't know if this
difference linearly increases. I m trying to read signal from the simulator
during the experiment, but we can't create a loop while the experiment
runs, maybe  because the stimulus is presented when E-prime "is waiting the
signal" and we don't want so.

So far, I didnt find any script line that makes this sync (i.e. read the
signal sent from the simulator) during the experiment, but only at the start
and at the end as described above.

About the possibility to use the simulator both for driving and for logging
mic responses, I cant do it; we need to use another pc.

I wish you can help me!

Thank you in advance

Francesco Biondi

2011/3/24 Michiel Spape <Michiel.Spape at nottingham.ac.uk>

> Hi,
> Did you just repeat the question? Anyway, the answer isn't much use, I
> would think; gigo, one might say.
> "i want e-prime to read this signal several times during the exp; how can i
> do it? best, which command i have to use to let e-prime do it? do you think
> it's possible let e-prime to read the signal every, for example, 20 minutes
> , or it's better send this signal from the simulator every cycle (100 cycles
> - 100 identical item - in 35 minutes) and let e-prime read it everytime?"
>
> This betrays a lack of knowledge of E-Prime, or poor wording, but in any
> case: E-Prime isn't very good at doing things in parallel or in terms of
> "read signal every 20 minutes", because it is heavily structured around
> principles that make sense for psychologists: trials, blocks, sessions. So,
> yes, if you want to read something every trial, or block, it shouldn't be
> too hard. But this depends on whatever you're doing with the experiment and
> your structuring so I, nor other people who lack telepathic abilities,
> cannot tell you. You might wish to start by explaining how the two systems
> are connected: serial cable? LAN? What are they doing? Is E-Prime merely
> logging your voice-key data, not presenting anything? In order to cope with
> drift, the two systems have to sync sometimes, therefore, connecting them
> will probably prove inevitable. This, in turn, may be less straightforward
> than you might think, so careful explanation is required for me to help you.
> Also, if E-Prime doesn't do much (other than logging voice-key), you might
> wish to just get rid of E-Prime and do everything in the simulator - have
> that log the voicekey thing.
>

>
> Best,
> Mich
>
>
>
>
>
>
>
> Michiel Spapé
> Research Fellow
> Perception & Action group
> University of Nottingham
> School of Psychology
> www.cognitology.eu
>
>
> -----Original Message-----
> From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf
> Of francesco biondi
> Sent: 23 March 2011 09:38
> To: E-Prime
> Subject: Re: Time drift between 2 different data streams
>
> Thanks for the answer.
> I m trying to send signals from the simulator to e-prime.
> i want e-prime to read this signal several times during the exp; how
> can i do it?
> best, which command i have to use to let e-prime do it?
> do you think it's possible let e-prime to read the signal every, for
> example, 20 minutes , or it's better
> send this signal from the simulator every cycle (100 cycles - 100
> identical item - in 35 minutes) and let e-prime read it everytime?
>
> On Mar 22, 10:33 am, Michiel Spape <Michiel.Sp... at nottingham.ac.uk>
> wrote:
> > Hi,
> > This is a weird problem, but I would assume (hope?) that the time you get
> from the simulator is the problem, not the one from E-Prime. If you think
> it's e-prime: do you have the latest version of 1 (1.2) or 2? Are you
> running E-Prime on some kind of laptop or computer with dynamic processor?
> > Anyway, this is why, generally, if you use two different data streams,
> you synchronise more often - try to implement that. Scaling the clock is
> unlikely to work, since it's very probable that the time drift isn't linear,
> so if, for instance, the time drift occurred halfway during the experiment,
> a linear correction would make ALL your data invalid, rather than half of
> it.
> > Also, you could try send live pulses from E-Prime to the simulator and
> just use all the data in there (or vice versa). A bit of work, but it saves
> despairing afterwards.
> >
> > Best,
> > Mich
> >
> > Michiel Spapé
> > Research Fellow
> > Perception & Action group
> > University of Nottingham
> > School of Psychologywww.cognitology.eu
> >
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On
> Behalf Of francesco biondi
> > Sent: 21 March 2011 16:12
> > To: E-Prime
> > Subject: Time drift between 2 different data streams
> >
> > Hello!!
> > I m using eprime in a experiment where a subject, driving a simulator,
> > has to use a microphone connected with a SRBox.
> > After merged the data from the 2 different data streams, i ve noticed
> > a time drift occurred between the 2 streams : e-prime times -
> > synchronized with the simulator times during the first part of the exp
> > - were drifted by the simulator times of 2.5 seconds at the end of the
> > experiment.
> > Do you know how i can solve this problem?
> > rescaling the eprime clock could help me?
> >
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-- 
*Francesco Biondi*

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