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Junior Member
 
Group: Forum Members
Last Login: 2/29/2008 11:43:41 AM
Posts: 18,
Visits: 68
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| I can't seem to get any control over the refresh rate on my PC. I have a couple of problems. Firstly, regardless of what refresh rate I choose in the display properties in Widows, E-Prime is indicating 75.013 as an actual refresh rate. Fine, this is no problem - I have just adjusted the timing of all my objects accordingly. Second problem - I have just set up a second monitor with a vga splitter so I can see a duplicate display of the experiment (this is an EEG experiment, so the stimulus monitor will be in the EEG chamber so I need a duplicate monitor outside the chamber so I can see what the participant is seeing!). Now, I can only achieve a refresh rate of 59.9 Hz as indicated by E-Prime. Why is the refresh rate dropping? Is it caused by the vga splitter? I really need refresh rates higher than 59.9 so I'm completely stuck now. I though perhaps the problem may have been related to using an LCD monitor as the "duplicate" monitor, so I swapped this for another CRT but I'm still having problems. It's very frustrating. I just want my refresh rate to stay at a constant 75hz so I can actually achieve accurate timing. Does anyone have any suggestions? 
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Forum MVP
Group: Administrators
Last Login: Today @ 9:12:01 AM
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| From the info you mentioned, it appears you are trying to specifically set your refresh rate as described in KB1299 - INFO: How do I set a specific refresh rate for my experiment?. My hunch is that you have an LCD since the majority of LCDs run at either 60 or 75 hertz. Check in windows display properties (control panel or right click desktop, select properties) for what type of monitor is selected. Typically plug and play will find this automatically (it will say Viewsonic P815, etc) or the generic "Plug and Play Monitor" will be selected. If possible try to find your specific monitor. If it is a newer model you may need to obtain an updated .inf from the manufacture. However, if you are running an LCD chances are the only two options available to you will be 60 an 75. Running an experiment with a dual monitor setup specifically configured where both monitors are showing the same content is not recommended. It is not clear which monitor E-Prime/OS will be sync with the vertical blank. As per questions on what values to put in the duration, I'd recommend truncating the value to be divisible by the refresh rate. So for 60 HZ, specify 16. Please analyze your data file to ensure the timing you intended is being delivered and then adjust duration, prerelease, and other values accordingly. -Brandon
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Forum Newbie
Group: Forum Members
Last Login: 2/28/2008 10:25:07 AM
Posts: 1,
Visits: 1
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I want to display an image near the edge of the screen for 30 ms. The refresh of the monitor is 75 Hz - I now know that this is not according to refresh guidelines. The resolution of the screen is set to 800 to 600. Is there any reason why it would display accurately on a CRT monitor, but have problems on an LCD monitor?
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Forum MVP
Group: Administrators
Last Login: Today @ 9:12:01 AM
Posts: 549,
Visits: 1,196
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| At 75 hz you could display the image for aprx 26 ms because 1 / 75 would provide that multiple of refresh rate using a CRT. If using an LCD, the image would be displayed for at least that amount plus whatever rise and decay properties the LCD offers. This really should only be determined by using external refresh dection equipment to determine this. Note that most LCD manufactures clain of 4ms, 8ms, etc are based on gray values and not from white to black and vice versa. KB3133 - INFO: Monitor Recommendations and Timing Information -Brandon
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