Testing e-Prime 2 Trigger Signal Timing in BioSemi

[isaacsda]

Hello,
I am using e-Prime 2.0 (https://pstnet.com/products/e-prime/) to conduct an auditory ERP experiment. I would like to test the accuracy and consistency of my trigger pulse from e-Prime to BioSemi. I am sending trigger signals through the USB-trigger interface but need to send a second "test" TTL pulse simultaneously, via a second serial cable, to allow for timing comparison between the two triggers, to measure error. I'm specifically attempting to quantify the inaccuracy in my computer's in-built sound card. Can you offer any guidance on how to set up this second simultaneous TTL pulse? Please let me know if my question is unclear or if additional information is needed to provide recommendations. Thank you in advance for any help.

[Coen]

Use the microphone (see https://www.biosemi.com/accessoires.htm) and compare the timing of the audio pulse in the ERGO channel with the trigger from E-prime.

Best regards, Coen (BioSemi)

[isaacsda]

Hello Coen,
Thank you for the above recommendation. I purchased the microphone and installed the Ergo channel as suggested, and I have verified these are functioning.
I am writing now with a follow-up software question about the same quality control timing check. I would like to convert the analog microphone signal to a binary gate (0/1) so that when a pre-specified amplitude threshold is crossed, a trigger signal is recorded at that time location. Then, the trigger signal from e-Prime can be compared to the trigger signal from the microphone.
-- How is the analog microphone signal denoted in the .bdf file?
-- Is there a particular point in the post-experiment signal processing where this analog-to-digital conversion for the microphone signal should occur?
Any guidance/insights are much appreciated!