Two issues about parameters in loading data

[Junying Su]

Dear OpenEphys developers, 

I have two issues about loading the ONIX data files.

https://open-ephys.github.io/bonsai-onix1-docs/articles/hardware/np1e/load-data.html

The first issue:

ap_recording = se.read_binary(os.path.join(data_directory, f"np1-spike_{suffix}.raw"), 3e5, np.uint16, num_channels, gain_to_uV=ap_scalar, offset_to_uV=-ap_offset)
lfp_recording = se.read_binary(os.path.join(data_directory, f"np1-lfp_{suffix}.raw"), 3e5/12, np.uint16, num_channels, gain_to_uV=lfp_scalar, offset_to_uV=-lfp_offset)

that is, ap sampling frequency = 300,000 Hz, lfp sampling frequency = 25,000 Hz. However, in Neuropixels 1.0 User Manual shown in the picture, ap sampling frequency = 30,000 Hz, lfp sampling frequency = 2,500 Hz. Why are these different?

The seond issue:

What is the meaning of 1.2e6? Is it related to the input voltage range in Neuropixels 1.0 User Manual?

Thank you.

[Junying Su]

[Junying Su]

An additional issue:

When recording data, the AP Gain and the LFP Gain are set to 1000 and 50, respectively. However, when loading data, ap_gain = 500 and lfp_gain = 500. Why are these different?

Thank you.

[Junying Su]

https://open-ephys.github.io/bonsai-onix1-docs/articles/hardware/np1e/gui.html

[Josh Siegle]

Hi Junying,

There's a mistake in the example code – the frequency values should be 3e4 and 3e4/12. I just opened an issue to correct this here: https://github.com/open-ephys/bonsai-onix1-docs/issues/214

You're correct that the 1.2e6 refers to the input range, which is ±0.6 V peak-to-peak, or 1.2e6 microvolts spanned by 10 bits of the ADC. I think the Neuropixels datasheet may be wrong here, I'm not sure where the ±5 mV value comes from.

For the AP and LFP gain settings, you'll need to substitute the values that were actually used during the recording.

Josh

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