Black Box IEEE 1284 Uživatelská příručka stáhnout pdf (Strana 38)

Page 38 of 98 The Black Box Toolkit

and measuring the distance between lines 1 and line 3. Below we can see that the audio

was played later than intended (line 1). It was actually late by 3 refreshes (line 3) or some

27ms (M) if you take the timings to the opto-detector positioned mid screen.

Our final measure is to check that there was a 1000ms delay after each trial before the

next commenced. Here we can see that the actual delay was 56ms longer than expected

(6 refreshes at 100Hz).

Accurate timing measures this give us the opportunity to alter the paradigm so that it more

closely matches our conceptual understanding. We may decide to reduce the duration of

the tone by 40ms in a sound editor if using a sound file. Thus when presented the duration

will be exactly 1000ms as intended. We could insert three black screen bitmap displays

before the visual stimulus begins. This would in effect move the onset of the real visual

stimulus back by 30ms so as to more closely synchronise with the start of the audio. We

could also decrease the wait period by 60ms to account for the additional 6 refreshes. The

wait period would then be as close to the intended 1000ms as possible.

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Black Box IEEE 1284 Uživatelská příručka Strana 38