This article applies to:
When using LCD monitors, consider that their timing characteristics are different from CRT monitors.
LCD monitors do not use the raster technology used by CRT monitors to redraw the screen. In E-Prime, most displays are synced with the vertical blank to avoid partial screen displays and to provide accurate timing. The vertical blank is determined by the position of the raster. Without being able to judge the position of the raster, PST cannot guarantee the synchronization of each display, nor guarantee that the reported refresh rate will be accurate.
In addition, LCD monitors typically have slower refresh rates than CRT monitors. In general, faster refresh rates will lead to more precise timing. Refresh rates for LCD monitors are typically around 60Hz, whereas refresh rates for CRT monitors can vary greatly, ranging from 60Hz to 100Hz or higher!
Thus, PST recommends that you use a CRT monitor when running experiments that require millisecond-accurate display timing. If running experiments on a laptop, attaching a CRT monitor will not have negative effects on timing as long as the display mode is set to 'Extended'. Do not set the display mode to 'Duplicate' mode because the timing information will report unexpected results. If millisecond-accrate display timing is not relevant to your experiment, or if the following latencies are acceptable, an LCD monitor can be used without issue.
When analyzing data, keep in mind the rise and fall times of the monitor being used. The rise time is the amount of time it takes a detector to go from a black screen to a white screen. The fall time is the amount of time that it takes to go from a white screen to a black screen.
It is possible to use an external device, such as the Black Box Toolkit (http://www.blackboxtoolkit.com/) to verify the timing of an LCD monitor. PST used the Black Box Toolkit's opto-detector to measure the rise and fall times of several different monitors.
The following are the results of PST's timing tests conducted with E-Prime 2.0.10.x:
|Monitor||Type||Connection||OS||Average Rise Time (ms)||Average Fall Time (ms)|
|Acer B223W||LCD||VGA||Windows 7||7.260||1.535|
|HP DV9700T||Laptop||n/a||Windows XP||10.480||not tested|
|Samsung 2243||LCD||VGA||Windows 7||6.900||2.820|
|Asus VG236||3D LCD||DVI||Windows 7||5.100||4.570|
|Viewsonic PF815||CRT||VGA||Windows 7||1.100||0.000|
|Viewsonic PF815||CRT||VGA||Windows XP||1.080||0.030|
|Hyundai LD90||LCD||DVI||Windows 7||7.670||3.400|
The following are the Legacy results from E-Prime 1.x:
|Monitor||Rise Time (ms)||Fall Time (ms)|
|ViewSonic P815 21-inch CRT||00.832||02.000|
|ViewSonic VX924 20-inch LCD||06.313||01.639|
|ViewSonic VP930b 20-inch LCD||08.64||02.058|
|Hyundai LD90+ 20-inch LCD||14.580||01.672|
|Dell 2005 FPW Widescreen LCD||28.667||25.668|
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