Open Ephys data Voltage Range

[Alessandro Leparulo]

Goodmorning Open Ephys community;

I have a question about the unit of measurement and the voltage range of the data recorded by Open Ephys acquisition system.

By re-inventing my recordings (32-channel passive probe in hippocampus), I noticed some inconsistencies in computing PSD powers by comparing them with old data (potentially born from a wrong scale factor) and I'm checking the new script, written by me, from the basics starting from .continuous data conversion.

Regarding some old discussions here on the forum (and I apologize for having resumed this discussion), it seems to me that for converting output data into µV, just simply multiply for the bitVolt coefficient present in the header, and in the datasheet, which is 0.195 µV (given by the gain factor Fixed at 192 V / V from the amplifier - in my case an Intan RHD2132).
Right?
What scale do the data originally have, before conversion?

Attached two images representing the same data channel before [original] and after [µV] the conversion.

Thank you all for your help and considerations!

Dr. Alessandro Leparulo, Ph.D.
University of Padua, Department of Biomedical Sciences - DBS

[Josh Siegle]

Hi Alessandro,

The raw data are saved as signed 16-bit integers, in the range -32768 to 32767. They don’t have a unit. To convert to microvolts, just  multiply by 0.195, as you noted. This scales the data into the range ±6.390 mV, with 0.195 µV resolution (Intan chips have a ±5 mV input range).

Does that explain the discrepancy?

Josh

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<data_100_CH_Original.jpg><data_100_CH_uV.jpg>