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bonsai-rx / ephys

Bonsai Library containing interfaces for acquisition and processing of electrophysiology signals
MIT License
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AdcScale -> BoardAdc bugged? #8

Open bruno-f-cruz opened 4 years ago

bruno-f-cruz commented 4 years ago

Hi,

When reading analog inputs using the open ephys acq board, of a signal that oscillates between 0-5V (confirmed with osciloscope and openEphys software), and converting it to SI units using AdcScale->BoardAdc, the output is not what I would expect and oscilates between ~1.8 (0V) and ~3.3 (5V).

I am using an Intan headstage, if that is relevant.

Thanks, Bruno

glopesdev commented 4 years ago

That is correct, unfortunately the ADC scale on the open-ephys system is different from the one specified in the RHD2000 eval board (the official RHD system from Intan). This happens because on the RHD2000 the analog inputs are unipolar from 0V to +3.3V while on the OpenEphys system they are bipolar with a range from -5V to +5V.

The current workaround is to use the ConvertScale operator to apply the correct scaling factor for SI units, which according to the GUI source is 0.00015258789.

You probably also need to use the Shift property to center the data around zero.

glopesdev commented 4 years ago

I will keep the issue open though as it makes sense to consider ways of addressing it.

bruno-f-cruz commented 4 years ago

Awesome thanks!