actiCHamp/actiCHamp Plus with BIP2AUX adapter

The actiCHamp/actiCHamp Plus is a modular, extensible amplifier system that allows the user to record peripheral signals via sensors from eight AUXClosedAuxiliary inputs. Up to 160 EEGClosedElectroencep- halography signals can be co-registered simultaneously with the AUX channels ( Figure 50 ).

Figure 50 actiCHamp/actiCHamp Plus amplifier with the actiPOWER battery. The BIP2AUX Adapter is connected to one of the AUX ports.

* acitCHamp is pictured, the setup is the same for actiCHamp Plus

The BrainVision Recorder workspace should be set as in Figure 51 if recording with the BIP2AUX adapter, given the following considerations.

The sampling rate should be set in the workspace depending on the characteristics of the signal recorded with the BIP2AUX adapter. The sampling rate set in the workspace applies to all recorded signals, therefore it should be chosen with the other simultaneously acquired signals (e.g. EEG) in mind. If needed, downsampling can be easily applied to the AUX channels individually offline.

The correct physical channel number must be indicated in the column “Phys. Chn” of the channel table in the workspace. The AUX channels always correspond to the last 8 physical channels, therefore in the BrainVision Recorder workspace settings, if you have only one 32-channels module, the AUX channels will correspond to physical channels 33-40, if you have 2 modules, the AUX ports will be physical channels 65-72 and so on.

The BIP2AUX adapter provides an amplification gain of 100. Hence, to set the correct units, gradient and offset in the channel table, check the box “Diff. Unit”, write “µV” as “Unit”, 0.1 as “Gradient” and 0 as “Offset”.

The other settings are dependent on your individual experimental requirements. For additional information about setting up a BrainVision Recorder workspace, please refer to the Recorder user manual.

Figure 51 BrainVision Recorder workspace settings for recording different peripheral signals with the BIP2AUX adapter. In the channels table, check the box “Diff. Unit”, write “µV” as “Unit”, 0.1 as “Gradient” and 0 as “Offset”. The other settings are dependent on the specific recorded signal.

Additional tips

Sampling rate

The required sampling rate depends on the purpose of the recording. For EOGClosedElectrooculography / Electrooculogram with the purpose of ocular correction, a typical EEG sampling rate is sufficient. Dedicated analysis of blink behavior would require higher sampling rate. ECGClosedElectrocardiography / Electrocardiogram for heart rate variability analysis also requires a multiple of the sampling rate needed to capture the ECG wave form. We suggested referring to the specific literature to choose the appropriate sampling rate for your study.

If using the actiCHamp/actiCHamp Plus in combination with BrainVision Recorder, it is important to consider that different low pass (hardware) filters are applied with each different sampling rate. For example, if a sampling rate of 2500 Hz is selected a low-pass filter with a cutoff at 690 Hz is automatically applied to the analogue signal (before digitization) in the actiCHamp/actiCHamp Plus hardware. With a sampling rate of 5000 Hz, the high cutoff is instead 1340 Hz.

Online filters

Using display filters may be useful for the correct visualization and assessment of the signals during your recording. For example, using a display filter with a low cutoff frequency of 20 Hz for EMGClosedElectromyography / Electromyogram recordings may allow a better assessment of the muscle activity, whose most prominent spectral components are above 20 Hz. A low-pass filter with a high cutoff frequency of 20 Hz will instead improve the online visualization of the ECG signal by removing artifacts of muscular origin.

A notch filter will reduce the effect of line noise (50 or 60 Hz depending on the country) in your online signal. However, reducing the sources of line noise in the environment is the preferred approach as spectral components at 50 or 60 Hz may be relevant for specific EMG analysis.

For more details on online filter settings in BrainVision Recorder, please refer to section 5 of the Recorder user manual.

Additional information on recording EOG with the actiCHamp/actiCHamp Plus can be found in our support tip: https://pressrelease.brainproducts.com/eog_actichamp/.