Editorial board editor-in-chief

Fig. 6.
 
Generated waveforms
The harmonics factor of a sinusoidal waveform doesn’t ex-
ceed 2,5% (Fig. 7):
Fig. 7.
Sinusoidal waveform distortion caused by harmonics
In the mixer we can get a signal described by following for-
mula: 
U
m
= xU
M 
+ (1−
x
)
U
N
where 
0 ≤ x ≤ 1
A solution like this guarantees that the EEG device will not 
be over-driven.
A very small (circa 10 ohms) output impedance of circuits 
(oscillators, mixer, modulator) makes the signal trace less prone 
to noise and interferences. This makes the testing conditions of 
the whole research better. 
Fig. 8.
EEG test signals generator
Shown on the back wall (Fig. 8) DB25 connector enables 
the use of an electro-cap cable.
Fig. 9.
Oscillogram of generated signals after passing through 
signal trace (256sps)

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81
Ima
ge
Pr
ocessing
Test-signal generators for Mindset MS-1000 electroencephalograph…
Fig. 9: channel 1 – sinusoidal waveform 2,8Hz, channel 2 – 
sinusoidal waveform 12Hz, channel 3 – signals from channel 1 
and 2 mixed with 50% + 50% ratio, channel 4 – analog product 
(multiplying) of signals 1 and 2.
The daemon is a source of data stream corresponding to the 
measured data coming from the Mindset MS-1000 EEG device. 
It is possible to replace the daemon with a software generator 
for testing purposes.
A solution like this makes it possible to develop and test 
modules without real access to hardware such as the interface 
card, the EEG device and the signal generator.
Fig. 10.
Front panel of software generator and examples of 
waveforms (128sps)