User Reference:gMOBIlabADC

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Function

The gMOBIlabADC acquires data from a g.MOBIlab device. g.MOBIlab is an amplifier/digitizer combination from g.tec medical engineering GmbH/Guger Technologies OEG (http://www.gtec.at).

g.MOBIlab Hardware

The MOBIlab device supports 8 analog input channels digitized at 16 bit resolution and sampled at a fixed 256 Hz sampling rate. In its standard configuration, channels 1-2 have a sensitivity of $\pm 100 μ V$ , channels 3-4 have a sensitivity of $\pm 500 μ V$ , channels 5-6 have a sensitivity of $\pm 5 m V$ , and channels 7-8 have a sensitivity of $\pm 5 V$ . The input range of the A/D converter is approximately equal to this sensitivity and thus, for example, one LSB for channel 1 or 2 is roughly $\frac{200 μ V}{65536} = 0.003 μ V$ . However, the actual input range of the A/D converter is slightly larger than the sensitivity of each channel (so that the A/D converter can detect when the amp saturates), and thus, exact LSB values have to be determined for each channel using a calibration signal.

This device only has one A/D converter and thus samples are digitized at slightly different times. BCI2000 has a feature that can align samples in time (parameter AlignChannels, which needs to be turned on (i.e., AlignChannels needs to be 1).

An additional feature of the MOBIlab is 2 digital input/output lines. The MOBIlab source module is configured such that channel 9 corresponds to the value of the digital lines, which are configured as input lines.

Parameters

COMport

Serial port of the attached MOBIlab device, e.g., COM2:

SampleBlockSize

Samples per digitized block. A value of 8 corresponds to a BCI2000 system rate of 32 Hz ( $\frac{8 s a m p l e s}{256 H z}$ ).

SamplingRate

The sampling rate of the MOBIlab. This value has to be 256.

SourceCh

The total number of channels. This number can be 1 to 9. If it is set to 9, then channels 1-8 represent 8 analog input channels, and channel 9 represents the values of the two digital lines.

States

None.