Page 72 of 112
CALIBRATION QUICK CHECK FOR 226 HZ
To initiate the quick check, select the Tymp only mode and insert the probe into the 0.5 cm
3
opening
on the test cavity. See Figure 1.
The instrument is designed to start automatically, it is important that the probe is inserted as quickly
and as smoothly as possible. During the calibration check, the probe must be held carefully and
without movement. Do not place the probe on the same counter as the instrument or any moving
object during this check as mechanical noise may be picked up by the probe and interfere with the
calibration check.
The calibration check will start automatically if the probe has been inserted into the cavity properly.
This is confirmed by the green lamp changing from blinking to a steady condition. If the
orange
lamp
is illuminated, the probe is not properly positioned within the cavity so that a large pressure leak exists.
If the
yellow
lamp is illuminated, the probe tip has been occluded. In either case, remove the probe
and wait for the blinking
green
lamp. Insert the probe once again. If necessary, clean the probe tip as
described later in this chapter.
The green lamp will resume blinking when the probe is removed from the test cavity. The
tympanogram on the display represents the response from the 0.5 cm
3
hard walled cavity. The ECV
(ear canal volume) should read 0.5. The letters NP will appear alongside the pressure (daPa) and
compliance (cm). Three dashed lines - - - will appear alongside the gradient (GR). Using the same
sequence, place the probe in the test cavity opening labelled 2.0 cm
3
. The resulting tympanogram
should be identical other than the ECV should read 2.0 cm
3.
The same sequence can be followed with
the 5.0cm
3
opening on the test cavity. To keep a record of this test cavity calibration check, simply
press the
button on the front panel of the instrument.
Since sound pressure will vary with altitude and barometric pressure, some variation from the 0.5, 2.0
and 5.0 cm
3
readings may be observed. The instrument is carefully calibrated at our factory, which is
at approximately 850 feet above sea level. An elevation of 1000 feet or higher, the instrument may
need to be recalibrated to account for elevation (see
Altitude Adjustment
in this chapter for more
details). It is not necessary to recalibrate for barometric pressure changes on a daily basis. Keep in
mind that a change in barometric pressure (i.e., from low to high or vice-versa) will slightly affect the
test cavity readings.
