Black Box IEEE 1284 Betriebsanweisung PDF herunterladen (Seite 61)

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simulated on line 7, 300ms after the leading edge of the visual stimulus display. This is the

“M” measure or the distance between the green cursor (A) and red cursor (B).

Note: The example above shows data collected when monitoring a TFT which has no

traditional refresh and so opto-detector traces are not made up as a collection of short

pulses where the opto-detector is illuminated as the beam of the CRT passes on each

refresh.

The best way to demonstrate use of the Data Analyser is with an in-depth tutorial.

8.5.1. Tutorial 1: Using the Data Analyser to check for visual stimulus duration

In this tutorial we want to discover how long a visual stimulus was displayed on a remote

PC. Ideally the bitmap would have appeared for 300ms. In this example a TFT is being

used on the remote PC and we do not need to be concerned with screen refreshes as we

might with a standard CRT.

We are specifically interested in line 3 as it displays the trace from one of the opto-

detectors. We can clearly see that a series of visual presentations on the remote PC was

detected during a 30 second run. The status bar indicates that approximately 1.5 million

samples were collected giving a sample rate of 49.70 samples per millisecond or 50kHz.

The current time and date are shown to the right of the status bar. The X-axis scale is

always in milliseconds and will initially display the whole run. On the Y-axis each of the

eight lines are shown with line 1 at the top and line 8 at the bottom. Lines 1 though 4 show

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Black Box IEEE 1284 Betriebsanweisung Seite 61