NuAmps drops samples

[Peter Quain]

good diagnostics (I think...). Only place it can be is a) Nuamps or 
b) faulty USB drivers (fromScan) causing sample loss at the 
acquisition computer.

We'd like some timing data from a few other systems (any Neuroscan 
amps, not just NuAmps) to check against our own. So if anybody is 
interested get in touch and I'll send along a test paradigm. Takes 20 
mins to loop through 310 trials. Do a couple of runs, then send along 
the output files (*.edat from e-prime, *.ev2 from *.cnt) and I'll 
send back some diagnostic output.


At 11:39 AM 23/06/2006, you wrote:
>How do you know that it isn't the eprime/stimulus computer that is 
>the problem?  Or, put another way, how are you certain that the 
>samples are dropped?  We've certainly observed missed triggers 
>before, but usually it is because the trigger duration was too short 
>relative to the sampling rate.
>
>-----Original Message-----
>
>From:  "Peter Quain" <pquain at une.edu.au>
>Subj:  NuAmps drops samples
>Date:  Thu Jun 22, 2006 5:13 pm
>Size:  958 bytes
>To:  "eprime at mail.talkbank.org" <eprime at mail.talkbank.org>
>cc:  "pquain at une.edu.au" <pquain at une.edu.au>
>
>
>
>Anyone out there using E-Prime with NuAmps?
>
>We've discovered that our NuAmps seems to be randomly dropping
>samples in what looks predominantly to be 11-12ms chunks, with
>another distribution around 36ms. The diagnostic paradigm (in
>E-Prime) runs trials and sends TTL pulse every 3600ms. Over 20 runs,
>of varying length (40, 130, or 310 trials) totalling 3000+ trials,
>4.1% exhibited sample drop > 9ms between successive pulses. This also
>happens, same basic pattern, using different computers to control the
>acquisition so unlikely to be PC related on the NuAmps side. The
>stimulus presentation computer appears to behave perfectly.
>
>Has anyone else identified a similar issue, or might it just be our
>unit / system?? No word back yet from Neuroscan on what the problem might be.
>
>Peter
>
>
>Peter Quain
>School of Psychology
>University of New England
>Armidale, Australia, 2351
>Phone:  02 6773 5193
>Fax:      02 6773 3820

Peter Quain
School of Psychology
University of New England
Armidale, Australia, 2351
Phone:  02 6773 5193
Fax:      02 6773 3820