Service manual

Neurodiagnostic Instruments Service Manual
6-24 Revised 2/18/05
Electrical Stimulator Problems
Is the VikingQuest or VikingSelect control panel
Stimulator LED blinking to indicate a STIM ON
condition? If so, is the Stim Probe connected to the
probe jack?
On the Endeavor CR, Is the STIM LED blinking? To
view the Stim LED, look though the ventilation slots at
the lower right side of the base unit case. The yellow
LED should be blinking whenever a stim pulse is being
delivered (The blue LED is a power indicator.)
Check the stimulator cabling for secure and proper
connections.
Run the USB/FireWire Diagnostics to verify the
condition of the electrical stimulator and probes.
Does the display show the amount of current to be
delivered? If it does not, verify that the proper
stimulator mode is selected (Console vs. Remote).
Display the Mode parameter and settings. Select
Remote when using the stimulator probe; select Console
when using the Stimulator Level dial on the control
panel or stimulating electrodes
Exit the VIASYS acquisition application and reenter the
test.
Testing Electrical Stimulator Specifications
If you suspect an electrical stimulator is not performing
to specification, you may check the stimulator output
using a 4 Kohm load and oscilloscope. Alternatively,
you can use the instrument itself as a digital
oscilloscope by connecting the stimulator output to a
load/attenuator test fixture and feeding the attenuated
signal to your system’s amplifier. The following
schematic diagram shows a suitable loop back test
fixture.
NOTE: Version 7.4 VikingQuest software does not
allow checking the electrical stimulator by
this method, as the amplifier is shut off
during presentation of the stimulus pulse for
purposes of stimulus artifact reduction.
Software version 8.2 features a Calibration
mode, where the artifact reduction feature is
turned off.
Procedure
1. Select a test mode that uses the electrical stimulator.
This might be NCS/MNC or EP/SEP.
2. Set up the following acquisition parameters:
Stimulus
- Rate: 5.3 Hz
- Duration: 1 ms
- Delivery: Recurrent
- Gating: Off
- Mode: Console
- Type: Voltage
- Range 400V
Display
- Timebase: 1 ms/div
- Sensitivity: 1 mV/div
- View Mode: View Input
- Delay: -5 ms
Amplifier
- LFF: 1 Hz
- HFF: 10KHz
- Sensitivity: 1 mV/div
4K Ω
500K Ω
10 Ω AmplifierStimulator
500K
Ω
/100K Loopback Test Fixture