From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2002-03-03 03:04:16
Abhayamudra Product Specification
EEG SPECIFICATIONS
------------------
General 4-ch EEG monitor and neurofeedback with
integrated Binaural Beat generator, flashing
LED glasses and binocular rivalry monitor
Channels 4 x monopolar + reference + neutral,
or 2 x bipolar + neutral (strappable)
A->D Sampling 8.196mSec (~122.07 Hz) Rate
A->D Resolution 10-bit precision, accuracy 9-bits or better
Anti-aliasing Switched capacitor 8th order elliptic filter
(r=1.2) LPF each channel, fc=programmable
3dB bandwidth 0.5 - 35/40/44Hz (60Hz countries) selectable
CMRR >95dB
Channel gain V/V: fixed 20k, or independently Ch1/2,
Ch3/4 10k-40k in 64 steps under ALC
(+-20%* absolute, +-2% ch to ch)
(+- 2% absolute to order)
* digital potentiometer spec
Driven Right Leg Sum of ch common mode, mains hum suppression,
current limited to IEC 60601
Probe health Measure of 2nd stage dc offset compensation,
measure each channel separately
Electrodes 6 x 80-160u" silver plated casings surrounding
saline impregnated sponge
Expected life: >3 months usage
Connector 8-way Modular
BINAURAL BEAT GENERATOR
-----------------------
General 2048 16-bit unsigned cosine lookup table
with interpolation
9 preset, 1 user programmable carrier frequencies,
10 preset volume settings (L & R)
9 preset, 1 user programmable beat frequencies
monaural pink masking noise, 10 preset volume settings
all in up to 8 sequences, each up to 9 minutes in 1
minute increments, or loop forever
Programmable 0.0 - 999.9Hz, 0.1Hz precision, 0.125Hz accuracy
Carrier Frequency
Range
Programmable 0.0 - 99.9Hz, 0.1Hz precision, 0.125Hz accuracy
Beat Frequency
Range
Preset Carrier 65.8, 73.6, 165, 197, 246, 393, 440, 492, 526 Hz
Freqs
Preset Beat 0, 1.2, 4.4, 6.6, 9.9, 13.2, 19.8, 26.3, 39.5 Hz
Freqs
Pink Noise Pinkish filter - 3dB/octave on white noise
algorithm (summation of staggered 1st order filters)
(also 4 octave Voss-McCartney to order)
White Noise Linear congruential (seed=16457)
algorithm (15-bit linear feedback shift register to order)
D->A Sampling 3.90625 kHz
Rate
D->A Resolution 8-bit
D->A filtering Switched capacitor 8th order elliptic
(r=1.2) LPF each channel, fc=1670Hz
Audio 3dB 80 - 1670 Hz
Bandwidth
Headset > 30 ohms
Impedance
Audio connector 3.5mm stereo
LIGHT GLASSES
-------------
LEDs 2 x 4 high intensity blue
Modes Left eye - right eye
Left field of vision - right fov
(selectable on glasses)
Sync flash - alternate L & R flash
(selectable on unit)
Connector 4-way modular/3.5mm stereo (I)
8-way modular (II)
BINOCULAR RIVALRY
-----------------
Abh II Display Left ocular field - vertical lines moving left
Rivalry Right ocular field - horizontal lines moving down
Abh I Display Necker Cube
L-R Converging tubes 40mm dia, 33cm long Discriminator
Eye Alternation 0.0 - 2.9 Hz, 0.1 Hz resolution Rate
PRESETS
-------
11 (I): setupEEG, focus, relax, release, intuit,
sleep, theWorks, external, user defined (3 off);
+2 (II): setup Probes, setup SigGen
MODES
-----
Binaural Beat Probes & feedback tones off
EEG Binaural Beat off, chimes or chords feedback tones
EEG+Binaural Chimes reward only, superimposed on
Beat Binaural Beat tones
EEG+Beat+Sweep Binaural Beat frequency sweeps between peak
EEG and target brainwave frequency, L/Rchosen
dynamically based on lower instantaneous
threshold value
DISPLAYS
--------
General 64x128 pixel chip-on-glass graphic display,
menu controlled contrast adjustment
Menus Rolling and scrolling menus and submenus
Probes Display Time domain Ch 1&2 or Ch 3&4, uVolt readout,
auto scaling analog gain/digital gain with
readout; linear Y axis, Ch 1&2 or Ch 3&4
Probes d.c. offset readout
Frequency Frequency Domain 0 - 60Hz , 1/f compensated,
Display Ch 1&2 or Ch 3&4, log Y axis, auto scaling
analog gain/digital gain with readout,
probes status
Mirror Display Left/Right Hemisphere Brain Mirror Ch ½ or
¾, Bands: delta, theta1, theta2, alpha,
beta1, beta2, gamma, pseudo log Y axis,
R/S ratio values, probes status
Coherency Phase space display of peak reinforce &
Display suppress band for previous ~120 FFTs Ch 1&2
or Ch 3&4, R/S ratio values, probes status
Centricity Spatial mean for Ch1 Reinforce band applied
Display to Ch 1/2/3/4, maker size reflects R/S ratio
amplitude for each channel, R/S ratio
values, probes status
Halleys Display Bat length is determined by R/S ratio for Ch
1/2/3/4 (left top, left bottom, right top,
right bottom resp., counts success in
deflecting ball, R/S ratio values, probes
status
Binaural Beat Sequence number, left frequency, right
Display frequency, beat frequency, left volume right
volume, pink noise level, time remaining,
R/S ratio values
EEG Log Display Previous 64 smoothed R/S values sampled each
~30sec, or Previous 32 logged R/S values
Ch 1&2 or Ch 3&4
Synchrony Instantaneous & smoothed values of complex
Display cross-correlation of FFT phasors in Ch1
reinforce band reflected over Ch1<>2,
2<>4,1<>3, & 3<>4, Range - 1.0 to 1.0
Samadhi Display Eyelids response to reinforce band amplitude
and R/S ratio resp, Ch 1&2 or 3&4, R/S ratio
values, probes status
Synchrony Log Previous 64 smoothed Xcorel. Values sampled
Display each ~30sec, or Previous 32 logged Xcorel.
Values, Ch F&B or Ch L&R
Eye Rivalry Left ocular field - vertical lines moving left
Display Right ocular field - horizontal lines moving down
Left-right dominance % readout, eye
switching rate readout Hz, auto boost flag
Eye Rivalry Log Previous 64 smoothed dominance & sw rate
values sampled each ~30sec, or
Previous 32 logged dominance & sw. rate values
Impedance Measurement of a.c. impedance of individual
(AbhayamudraII electrode-scalp impedances at 30Hz. Range:
only) 0..125Kohm ± 2K ohm. Auto calibration feature.
Signal Generator 2-tone mode: F1 & F2: 0.0..49.9Hz,
(AbhayamudraII 0.0..39.9uVpp*, individually settable
only) Sweep mode: Flo & Fhi: 0.0..49.9Hz,
0.0..39.8uVpp*, rate 0..59 seconds
PROTOCOL
--------
General Select reinforce & suppress band for each of
4 channels. R&S can be any of delta, theta1,
theta2, alpha, beta1, beta2, beta3, or
gamma. R/S calc based on digital filters
(~65mSec response), X-correlation calcs &
displays based on FFT (130+mSec response)
Artefact Delta change in Spectral energy measured &
Suppression compared with threshold -> inhibit rewar
DIGITAL FILTERS
---------------
General Elliptic 4th order BPF, 2nd order Direct
Form II cascade implementation with Q15
format coefficients, 10-bit data
Delta 3dB 0.6 - 3.0 Hz, pass 0.7dB, reject 48dB
Bandwidth
Theta 1 3dB BW 3.5 - 4.8 Hz, pass 0.1dB, reject 49dB
Theta 2 3dB BW 5.7 - 7.6 Hz, pass 0.1dB, reject 48dB
Alpha BW 8.5 - 10.7dB, pass 0.1dB, reject 48.5dB
Beta 1 BW 11.8 - 15.0 Hz, pass 0.1dB, reject 48dB
beta 2 BW 17.2 - 21.5 Hz, pass 0.1dB, reject 48dB
Beta 3 BW 24.5 - 34.0 Hz, pass 0.1dB, reject 44dB
(53dB @ 50Hz)
Gamma BW 38.0 - 43.0 Hz, pass 0.1dB, reject 44dB
(60dB @ 50Hz)
FFT
---General 1:N input overlapped, raised-cosine windowed, scaling 8-bit Radix2 (8 - 256 points), 2-ch (Ch A real, Ch B imaginary), in-place, complex FFT
Overlap 4:1
Points 64
Window Pseudo Hamming raised cosine
Lookup table 64 point signed 8-bit cosine table
Power Spectrum Pseudo power spectrum using coeff magnitud as proxy
AURAL REWARD ------------
Dynamic Reward triggered by fuzzy logic inference threshold engine - inputs are current R/S ratio, R/S ratio history, time duration to previous reward hit. No manual setup required.
(i) Chords 2048 16-bit unsigned cosine lookup table, monaural, Base=440Hz, 3rd=550Hz, 5th= 660Hz, 7th=825Hz; ADSR=50/150/600/200mSec resp (not available in Bbeat mode)
Algorithm Chord: any 1 R/S->chord 1,any 2->chd 1+2, (menu selectable) any 3->chd 1+2+3,all 4->chd 1+2+3+4 ChordSync: any 1 Xcorel->chord 1 etc
(ii) Chimes .wav files for lo, lo-med, med, med-hi, & hi
Algorithm R/S LF OR LB(L)/RF OR RB(R), LF AND LB(L)/RF (menu selectable) AND RB(R) Sync: LFLB Xcorel.-> chime1(L),RFRB->chime2(R), LFRF->chime3(L+R), LBRB->chime4(L+R)
(iii) Continuous Pitch varies in accordance with R/S Variable Pitch
Algorithm Left channel: Ch1 or C3; Right channel: Ch2 or Ch4 Sync: Left channel: Ch LF-RF or Ch LF-LB, Right channel: LB-RB or RF-RB
ELECTRODE IMPEDANCE METER (Abh II) -------------------------
Measurement Inserts 30.5Hz signal into Neutral electrode technique and measures individual signals on other five electrodes. Current is limited to IEC 60601 values plus margin. Measurement is sequenced through five electrodes with four cycles of 30.5Hz for each measurement -> ~0.625 sec for each pass. Two measurement points allows discrimination of Neutral & other electrode impedance.
Measurement Sum of each of electrodes in series with range Neutral electrode < 256K W in 1K W steps. (eg if Neutral electrode is 50K W , maximum measurement for other electrodes is 205K W )
Accuracy: Uncal: ± 3K W ; Cal: ± 1K W Reference electrode
Accuracy: Ch1..4 Uncal: ± 4K W ; Cal: ± 2K W electrodes
Accuracy: Uncalibrated: unspecified; Calibrated: ± 10K W Neutral electrode
Calibration Utilises external eeg cable termination (supplied)
mVolt SIGNAL GENERATOR (Abh II) ----------------------
General Utilises external passive attenuator (supplied) Frequency range: sine wave, 0.1..49.9 Hz (Abh II) Frequency accuracy: ± 0.1Hz Amplitude range: 0.0..39.9 m Voltp-p Amplitude accuracy (@ 0.0..30.0uV; 1..49Hz): ± 0.5m Voltp-p (includes coupling capacitor pre-compensation) Amplitude accuracy @ 0.1Hz: -50%
Sweep Mode Single tone of amplitude set 0..40m V sweeping between f1 & f2, each selected in band 0..50Hz, at a selectable sweep period of 0..59 secs. Note some combinations of sweep breadth & sweep period will be below minimum sweep rate of 0.5Hz/sec causing sweep to not proceed beyond f1.
Two-tone mode Two constant tones each individually programmed frequency 0..50Hz and amplitude 0..40 m Voltp-p
INFRARED LINK (Abh II) -------------
General Frame consists of sync/data byte + 2/4 channel data bytes (Tx & Rx). 6-bit data alternates between status & command info. Rx data may add to or replace locally generated data, 2 x 9-bit samples in burst, then window to receive burst, if no receive then use local data
Protocol Pseudo ping-pong, peer-to-peer, Peak wavelength 870nm
Rx sensitivity 62.5nA (~40-200nA to order)
Range ~50cm
Format 1 start, 8 data, pseudo even parity*, 1 stop; *9th bit: no parity error=0, error=1
Rate 384k Baud
Synchronisation Count 0..3 (prefix of each sync/data byte at start of frame)
Status Info Left/Rigth button, Ch1/2/3/4 probe status
Commands Pause/resume, 2/4 ch, ALC on/off, EEG local/remote/mix, 8-bit,9-bit(parity) word
REAL TIME CLOCK ---------------
Format HH:mm (24 hr) DD:MM, auto day of month & leap year corrections
Alarm Matching HH:mm; if unit operating-> turn off, if off-> resume at previous settings
Accuracy ~± 4min/month (~± 30sec/month to order)
TEST MODE ---------
General Menu selection of test mode, except for strappable selection of left/right earpiece tones insertion into Ch 1/2 or ¾ for EEG hardware testing
EEG bandwidth 62.5Hz (to observe induced mains hum), 1/f compensation removed
Left/Right 7.63/3.815 Hz square wave resp. (to ensure earpiece headphones orientation is correct)
MULTITASKING DISPATCHER -----------------------
Startup thread Power up control
Menu thread Controls scrolling of menus, input of config. commands, execution of commands
Main thread Controls main program loop: fft, dig filters etc, when unit active
Go thread Controls inputs when unit active
COP thread Controls servicing of watchdog timer when unit is active (reset upon software error)
Activity thread Controls unit shut down in absence of regular inputs (power save)
Bitbang thread Controls slow serial port control of peripherals (dig pot) (noise reduction)
Stop thread Controls power down of unit
POWER MANAGEMENT ----------------
Power < 100mA @ nom 3.6Vall times, <100uA Consumption in power down
Battery 3.6V Nicad, 600mAH
On-time >5 Hrs continuous, >1 month in power down (after overnight charge)
Battery life ~ 1 year, regular use, regular charging.
Charging 6-12Vdc >100mA charger, 20mA trickle (overnight full charge)
Operational Disable unit upon charging, "Lo-bat" flash, measures power down after 5min. idle timeout when in startup mode, after 2 min in menu mode, after two hours 15min whilst operating, "place on charger" warnings
Connector 1.3mm power jack, positive centre pin
CASE ---- General Active components fully enclosed by case (except connectors) - no exposed metal parts
Material ABS GSM UL rated 94 HB plastic, ~2mm
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:39 BST