Service Check Using The Loop Back Box (Lbk15) - Interacoustics Eclipse Additional Information

Eclipse Additional Information
2.3

Service check using the Loop back box (LBK15)

The ABR system can be tested using the loop back box LBK15. The test can be used to check the recording
and stimulating circuits of the Eclipse and the Preamplifier with attached cables.
Note that the LBK test can only be used for testing the EP15/25 system and is not valid for functional testing
of the ASSR and ABRIS detection algorithms.
1. Testing the electrical stimuli and recording path
Connect the loop back box to the pre-amplifier using the cable with electrode buttons and connect the
LBK15 jack plug to the right (red) or left (blue) headset channel on the Eclipse.
2. Start the EPx5 software and select the LoopBack - LBK15 from the protocol list.
3. Check the Preamplifier impedance circuit. Choose Impedance mode (IMP) setting on LBK15 and Pream-
plifier and turn the impedance knob on the pre-amplifier to around 3kOhm. The LED´s must change from
red to green when the impedances on the artificial patient (LBK15) are below 3kOhm.
If it does not turn green around 3kOhm, it can indicate a broken electrode cable or preamplifier cable. Ex-
change the broken part.
While Impedance mode is enabled the EEG will indicate full rejection on the screen.
Press the Imp button on the preamplifier again when finished to turn off Impedance mode.
4. You should be able to perform the test with an input gain of +/- 40µV. The EEG curve should be black be-
fore you start the test. Repeat the test on the other channel if both must be tested.
Note If the EEG curve is red it can indicate no/poor ground is connected to the Eclipse or you have to
search for noise sources (see the section "Limiting noise in the test environment" to help you locate the
noise source).
5. To check the signal output, start the test. The evoked potential for right and left with an output at 80dB
should be similar (in fact they are never 100% similar as the individual calibrated transducers are not con-
nected), see picture example below. If one is much smaller/bigger than the other there might be a prob-
lem with the pre-amplifier or output stage to the transducers in the Eclipse, perform a listening check of
the transducers to check if the output are similar.
An intensity deviation can be adjusted with a software calibration (see the service manual for calibration
guidance).
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