Black Box IEEE 1284 Guía de usuario descargar pdf (Pagina 46)

Page 46 of 98 The Black Box Toolkit

By measuring the first “on” event we can see that it lasted exactly 1000ms as intended. By

comparing the sequence generated with that recorded by the remote PC we can calculate

the amount of timing error.

8.3.2. Tutorial 2: Simulating the TTL synch pulse from an fMRI scanner

It can be useful to simulate TTL pulses that an fMRI scanner produces. These can be used

to check that they are being recorded and acted upon correctly by third party hardware

and software running on a remote PC. By default TTL pulses generated can be very short

in duration, e.g. 0.005ms (Philips Intera scanner). However, it is assumed that most

researchers will have increased the dynamic pulse width to around a millisecond or above

as this can easily be accomplished in the scanner software. Using the Event Generator we

can simulate TTL pluses that are a millisecond wide.

We start EG as normal but as we may want to generate a sequence of pulses that may

consist of hundreds of events we wouldn’t wish to define each one individually. This is

where we can make use of the “Auto Sequence Generator”. To use this utility press “F2” or

click on “Tools|Auto Sequence Generator” from the menu bar.

To use the generator we need to know several pieces of information.

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Black Box IEEE 1284 Guía de usuario Pagina 46