FONIX® FP35 Touch - Frye Electronics

Coupler Measurements 89
8. Test as desired. Make sure not to change the strength of the magnetic field
from the TMFS setting.
3.8.9 Measuring with an External Signal
Measurements with the FP35 analyzer are typically performed using the internal
signals available in the analyzer, such as puretone sweeps, Composite or
the Digital Speech signal. However, you can also use an external signal from a
device such as a CD player or an MP3 player using the “line-in” 3.5 mm jack
on the back of the analyzer (available on instruments manufactured November
2008 or later).
You will need the Composite/Digital Speech Option to use this feature.
Connecting the External Source
Connect the FP35 to the external source by using the 3.5mm “line-in” jack on
the back of the analyzer. If your analyzer does not have this jack, then it was
probably manufactured previous to the addition of this feature. Existing analyzers
can be upgraded. Contact your FONIX distributor for details.
Setting up the FP35
To use an external source for coupler measurements:
1. Enter the Coupler Multicurve screen by pressing the [F3] key from the
Opening screen.
2. Use [F4] to set the source type to COMP.
3. Use the [q] key repeatedly until the source is OFF. This puts the analyzer in
“spectrum analysis mode.”
4. Press [START/STOP] to start the measurement.
5. Turn on the signal from the external player. The signal should now be playing
from the FP35 speaker.
Calibrating the External Signal
We recommend that you calibrate the external signal for best measurement
results. Many CDs used by hearing health professionals contain a calibration
track as the first track of the CD. This is generally a puretone signal at a particular
input level.
To calibrate the signal on the FP35:
1. Position the coupler microphone in the sound chamber at the reference
point (middle of the white circle).
2. Put the analyzer in spectrum analysis mode and play the calibration track
on the CD through the FP35 speaker using the setup described above. Make
sure to start a measurement by pressing the [START/STOP] key.
3. Adjust the volume control on the external player until the RMS OUT matches
the desired level of the calibration tone. This level should be indicated in
the instruction materials of the CD.