mains supply using switch S2. Check that the
current does not exceed 500µA a.c. and 50µA d.c.
Switch off the unit and remove all connections
between the unit and the special test equipment.
Connect the unit directly to the mains supply,
switch on and wait for Windows 95 to “boot up”.
5.10 EMG Safety Checks
The tests in this section should be performed on
both Stim A and Stim B (if fitted).
5.10.1 Stimulus Fail Condition (Current Mode)
From the “Stimulus” drop down menu select
“Electrical Stim Setup” (see ). Set the Output to
Current and the Range to High. Click on OK to
return to the acquisition screen.
Connect the 3k3 load across the stimulus output
connectors. Monitor across the load with the
oscilloscope, connecting the probe earth lead to the
black connector.
Using the control panel controls, set the Duration
to 500µs and Rep Rate to 30pps. Set the stimulus
level to 100mA.
Press STIM to turn on the stimulus, and check that
a “Stim Fail Condition” error message is
repeatedly displayed.
Set the stimulus level to 0mA, and check that the
error message stops re-appearing.
Press STIM to turn the stimulus off.
5.10.2 Overcurrent Checks
Set the Output to Voltage and the Range to High.
Replace the 3k3 stimulus load with the 100
Ω
stimulus load and monitor across it with the
oscilloscope as before. Increase the stimulus level
to 300V. Press STIM again and check that the
stimulus pulse displayed on the oscilloscope is
now 10V±1V.
Press STIM to turn the stimulus off.
5.10.3 Stimulus Fail Condition (Voltage Mode)
Connect the 2k7 load across the stimulus output
connectors and monitor across it with the
oscilloscope. Set the stimulus level to 300V.
Press STIM to turn on the stimulus, and check that
a “Stim Fail Condition” error message is
repeatedly displayed.
Set the stimulus level to 0V, and check that the
error message stops re-appearing. Press STIM to
turn the stimulus off.
5.10.4 Mark/Space Failure
Connect the 3k0 stimulus load across the stimulus
output sockets and monitor across it with the
oscilloscope. Set the stimulus level to 50V and
press STIM. Set the Repetition Rate to 100pps
and increase the Duration in stages.
Check that when the pulse duration is
≥
500µs, the
stimulus pulse amplitude displayed on the
oscilloscope immediately falls to 0V, and a
“Mark/Space Shut-down” error message is
displayed. If testing a stimulator probe, check that
neither polarity LED is illuminated indicating that
a shut-down has occurred.
5.11 Audiometric Headphone Cut-Off
Checks
Plug the Audiometric Headphone set into the
u
connector on the Connection Unit but do not put
them on !
Click the Test Menu button and select the CERA
test.
From the Acquisition / Setup ... screen, set the
Frequency to 1kHz, Intensity to 125dbSPL,
Plateau to 960ms, Rep. Rate to 1pps, Random to
Off, Envelope to None and Masking to Off. Click
on Ok when finished.
When the the Acquire function button is clicked,
cautiously listen for tone from the Left Headphone.
Check that after approximately 3s the tones are
switched off and a message box The system has
detected an EP Stim Audio Overload is
displayed. Click on the Ok button.
Click on Acquire again.
Repeat the above setup. Click on the Other side
function button, then click on the Acquire function
button. Cautiously listen for tone from the Right
Headphone.
Check that after approximately 3s the tones are
switched off and a message box The system has
detected an EP Stim Audio Overload is
displayed. Click on the Ok button.
Click on Acquire again.
Close the Synergy Mobile application and then
shut down Windows 95. Switch off the unit and
disconnect all test equipment.
PATIENT SAFETY CHECKS
Issue A May 1998
Synergy Mobile Workshop Manual
Chapter 5 Page 5