bci2000.org BBS

Hi all,

I am confused about how to calculate SourceChGain value. For example, if we have an amplifier with gain 100, a 16-bit DAQ with the range +\- 5V (which is =+\-5e9 muV), and assume SourceChOffset=0, then should the SourceChGain be:

SourceChGain = 10e9/(100*2^16) =152.59 ?


Thanks in advance!

Xiang

Hi,

1V is 1e6muV, so you have SourceChGain = 0.15259.

Regards,
Juergen

Thanks a lot!

Xiang

Hi Juergen,
How are you?
I have a similar question, which is related to EGI and AmpServerProADC.
I am using EGI 300 amplifier, which has a range of +/- 200,000uV that is digitized into
a 24bit signed value. And the gain for this amp is 20.
According to the equation described by Xiang, SourceChGain = 4e5 / (20*2^24) = 0.001192.
However, in the code of AmpServerProADC

( PreflightCondition(fabs(Parameter( "SourceChGain" )( ch )-0.0238)<(1E-3) );

, the value is confined in (0.0228, 0.0248), almost 20 fold difference from the value calculated above. it seems to me that the gain used in the code is "1", which is not consistent with the hardware specification.
I am just wondering if this may be a bug for the AmpServerProADC. Please correct me if anything is wrong. Thanks a lot!

Hi Ran,

in your case, amplifier and digitizer are integrated, and the amplifier/digitizer's sensitivity is directly given in microvolts. Thus, there is no need to divide by an amplification factor, and you obtain the value from the AmpServerProADC.

Regards,
Juergen