Time drift between 2 different data streams

[Michiel Spape]

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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