Photodiode Latency

Hi,

We have connected the digital output of a photodiode to ML. Info about the monitor setup is as below:

Monitor - Elo 1593L Touchscreen
Resolution - 1024 x 768
Refresh Rate - 75 Hz
Photodiode location - Upper Left
Photodiode - amazon store link

We have attached the following screenshots of the tool dialog box:

010.png - This is what's displayed as the tool opens. (note - we ran with threshold at 0 but the result was the same)
020.png - The tool display after running automatic tuning .

According to what we have understood about the tool, the plots show that the photodiode response lags the flip command time by a large margin and automatic tuning also fails. Would you be kind enough and help us diagnose the issue we might be facing here?

Thank you,

Thomas

The tool expects HI when the white square is presented.
https://monkeylogic.nimh.nih.gov/docs_MainMenu.html#Video

But your signal is HI even before the square is presented. Is your signal inverted TTL?

Sorry for the delayed response Jaewon. We flipped the signal polarity and the problem persists, i.e. a threshold was not found by the automated threshold tuning.

You need to show at least your new test result. There can be so many reasons why it does not work.

NIMH ML already uses a lead time long enough for most systems (one tenth of the refresh interval), so, unless you are using a FHD or 4K monitor for the subject screen, it shouldn't be a big concern.