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4 DISCUSSION
SimPac I carried out all the expected basic functions.
Several improvements were made regarding the
previous prototype (SPEA): ECG and ENG signals,
inclusion of performance signals intended to be used
on amplifiers and filters verification (sine and
square), inclusion of optical isolation in the external
trigger input, new user interface using GLCD,
function keyboard and soft starter. A circuit for USB
communication was added to make easy the future
inclusion of new signals to simulate.
For next version we intend to add a white noise
generator to simulate the EEG signal in which the
auditory evoked potential is immersed. That
characteristic will allow extension of the tests of
AEP equipments to the averaging quality.
Some simulators in the market generate
waveforms through complex mathematical formulas,
demanding digital signal processors for its
implementation. SimPac I generates the waveforms
from samples tables by DDS, and the execution can
be made through a simple microconverter. The
SimPac I main advantages are: the generation of
signals that resemble those observed on biological
systems, however with known amplitudes and
latencies; the generation of signals with excellent
repeatability; the substitution of the patient or
volunteer during the development of medical
equipments; and also in development, the
elimination of undesired factors of difficult control,
such as the electrode-skin impedance, other
bioelectric signals like spontaneous EEG or EMG,
and electromagnetic interference.
5 CONCLUSIONS
In this work we demonstrated the viability of
creating an equipment intended to simulate AEPs of
several types, ECG, ENG and performance test
signals. SimPac I simulated signals were verified
through a commercial system for AEP acquisition
and a digital oscilloscope, showing reliability and
precision in the requirements of synchronism,
amplitude, timing and repetition. The use of this
simulator can facilitate the software development
and validation for processing AEP, ECG and ENG,
as well as the hardware adjustment in production,
and the preventive and corrective maintenance of
electro-medical equipments.
ACKNOWLEDGEMENTS
The authors thank to Brazilian Agency CNPq by the
financial support under the grants 507363/2004-3,
310611/2005-9, 120005/2007-7 and 310058/2007-4
(DTI and ITI scholarships) and also to the designer
Leonardo de Jesus Furtado by the SimPac I layout
project.
REFERENCES
Analog Devices, 2003. MicroConverter 12-bit ADCs and
DACs with Embedded High Speed 62-kB Flash MCU.
Analog Devices Inc. Norwood.
Caovilla, H. H., 2000. Audiologia Clínica. Atheneu. São
Paulo.
Castagno, L.A., Tavares, M.C., Richter, C.M. et al., 1994.
Sistema Computadorizado de Eletronistagmografia e
Vectonistagmografia “UCPel/Castagno” (Versão 3.0).
Anais do IV CBIS, pp 26-31.
Chiappa, K. H., 1997. Evoked Potentials in Clinical
Medicine. Third Ed.. Lippincott-Raven Publishers.
Philadelphia.
Contronic, 2007. Manual do Usuário - Módulo de
Aquisição de Sinais Bioelétricos – MASBE – Rev. 4.
Contronic. Pelotas.
Contronic, 2007a. Manual do Usuário - ATC Plus -
Software para Audiometria de Tronco Cerebral –
Build 2.1.X – Rev. 4. Contronic. Pelotas.
Freitas, G.M., Oliveira, T.R, Moraes, R. e Tavares, M.C.,
2006. Simulador de Potenciais Evocados Auditivos de
Curta, Média e Longa Latência Baseado em
Microconversor. Anais do CBEB 2006, v 1, pp 1224-
1227.
Grover, D.; Deller, J. R.; 1999. Digital Signal Processing
and the Microcontroller. Motorola University
Press/Prentice Hall PTR. New Jersey.
Katz, J., 1999. Tratado de Audiologia Clínica, Ed. 4.
Manole. São Paulo.
Prutchi, D., Norris, M., 2005. Design and Development of
Medical Electronic Instrumentation. Wiley. New
Jersey.
Wickenhäeuser, 2005. uC/51 V1.20.04 User´s Manual.
Wickenhäeuser Elektrotechnik. Karlsruche.
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