Sensorium DADBPA-1

The DABPA-1, digital EEG/ERP AC bio-potential amplifier, represents a marriage of current state of the art analog and digital technologies, providing the most refined surface potential recording instrument available. With the advent of ultra-stable low power and low noise buffer amplifiers, recording from electrodes of resistances to 200Kohm is realized by a small differential pre-amplifier. Noise and drift from previous amplifiers barely fulfilled the requirements for 12 bit in computer data acquisitions boards. The DABPA-1 incorporates components with of the order of fifteen times the accuracy and stability of the previous generation amplifiers, making possible a four times improvement in resolution with 16-18 bit digitizers. Coupling of environmental noise onto digitizer has been all but eliminated by placing the analog to digital converter next to the signal conditioning circuitry.

• Signals from high resistance electrode contacts drive a very high impedance, high common mode rejection, AC servo controlled pre-amplifier, sized for positioning close to electrodes
• Measure the resistance of an entire bank of electrodes concurrently
• High pass filtering . 2 poles . four corner frequencies . digitally programmed
• Gain . cascaded stages . four settings each . digitally programmed
• Low pass filter . 4th order Bessel filter
• High resolution analog to digital converters
• High performance digital signal processor
• Digital galvanic isolation
• USB2.0 high speed serial connection to host computers
• Modular . expandable in 64 channel increments to 256 channels
• Low level module to digitize from a variety of sensors
• Event stamping of external stimuli in the data stream

	Features
	Feature Benefit Concurrent electrode resistance measurement Short electrode preparation time, at a glance measure of the state of electrodes Short electrode preparation time, at a glance measure of the state of electrodes Short electrode preparation time, at a glance measure of the state of electrodes Effective high pass filtering Good for cortex and brain stem studies Modular - expand in increments of 64 channels Easily adapted to new experimental paradigms Multi-mode operation Access to + and - inputs, and digitally controlled turn-off of individual channels Sine wave calibration source No external function generator necessary Miniature stand alone pre-amplifier Less noise, higher electrode impedance, excellent low frequency stability Systems operate in parallel Expansion in increments of 64 channels High resolution ADC Multi-referenced montage Better signal to noise ratio Wide dynamic range Powered by the mains No batteries to recharge Digital isolation by micro-machined air transformer No analog signal deterioration AC power supply separated from DC electronics No AC radiator close to recording site

	Circuit Design
	Feature Benefit High Input impedance Less error from electrode impedances drift and mismatch High CMRR High immunity to environmental noise Bi or mono polar Record with or without reference 5th order low pass filter Effective filtering of high frequencies, excellent anti-alias filter Servo high pass filter Wider range of offset potentials, wider dynamic range High pass corner frequency accurate to +/- 1% Excellent channel to channel phase characteristics Very low noise Very high signal to noise ratio recordings Digital opto-coupling of control lines Eliminates ground loops and isolates the recording subject

	Design Safety
	Feature Benefit Digital Signal - Magnetic Isolation Protects from off ground currents and loops Input protection (optional) Protects from high voltage assaults and ESD Power Supple - Magnetic isolation Protects from line source ground fault

	Specifications
	Input impedance: 5G-ohm, differential with high impedance input connector Common mode: >110 dB, 1st stage 50X DNL and INL: +-1.5 lsb High pass filter: 12 dB/octave: 4 settings Low pass filter: 4th order Bessel, Butterworth, Elliptic Electrode Testing: 1 uA p-p, 20Hz Gain accuracy: <0.01% of selected value, eight settings Noise: <0.2 µV p-p 0.1-10 Hz <1.5 µV p-p 0.01-55 Hz <3.5µV p-p 1 Hz - 3 KHz (referred to input) Bandwidth: DC - 5 KHz Isolation: 2500 Vrms, 60Hz, continuous Host Interface: USB 2.0