Service manual

Neurodiagnostic Instruments Service Manual
3 - 62 Revision 2/18/05
ES-8 IOM Amplifier Block Diagram
The block diagram on the next page shows the
functional components for the VikingSelect 8-channel
IOM amplifier.
Electrodes from the patient plug into one of two
headboxes, which are in turn connected to the amplifier.
Crosspoint switches in the amplifier route the electrode
signals to any of the eight amplifier channels where they
are amplified by a factor of 100, 1000 or 10000. The
signals also flow through a High-Pass Filter (HPF) and a
Low-Pass Filter (LPF) where selective frequency bands
are attenuated.
The remaining stages are identical to those found in the
EA-2 and EA-4 amplifiers described earlier.
Stimulus Artifact Suppression is implemented in the
amplifier and may be used to help counter the effects of
electrical stimulus on the measured patient signals. This
feature may be applied to individual channels or may be
enabled or disabled globally.
Testing
The VikingSelect FireWire Diagnostics are the primary
tool for testing the amplifier system. The AutoTest
checks for proper communication between the base unit
and amplifier module, and the Headbox Test uses an
internally generated calibration pulse to check the signal
path integrity farm the electrode input connectors on the
headbox to the host computer.
ADC2
ADC1
+15V
Mux
Mux
Cal/Z
Source
Temp
Ch1
Ch2
Ch3
Ch4
Mux
Mux
Control Logic
Mux
A
Mux
B
IEEE 1394
Interface
2 Channel
Audio DAC
DSP
DC-DC
Converter
Opto-Isolators
Ch1 Ou
t
Ch2 Out
I+8V
I+15V
I-15V
Isolation
Barrier
Ch1 Hybrid
Ch4 Hybrid
Ch3 Hybrid
Ch2 Hybrid
VikingSelect EA-4 EMG Amplifier Block Diagram