Welch Allyn GSI 38, Руководство по обслуживанию

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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. Clean the probe tip if necessary (XXXXXX).
When the test sequence is completed, the green lamp on the probe is no longer
illuminated. Remove the probe from the test cavity and note that the green lamp is
blinking once again. The display will indicate a flat line on the tympanogram along with
the value of the test cavity next to the letters ECV (ear canal volume) i.e., 0.5. The
letters NP will appear next to the labels cm 3 and daPa and three dashed lines will
appear next to the letters GR (gradient). Since the test cavity is a hard-walled cavity,
the tympanogram should be a flat line indicating that there is no mobility in the system.
The GSI 38 places the letters NP next to the cm
3 and daPa headers to indicate that
there is no peak compliance and, therefore, no peak pressure can be determined
during the quick check. Also, since there is no compliance peak detected, it is not
possible to calculate a gradient. Therefore, the GSI 38 displays the dashed lines when
a gradient calculation isn’t possible. Using the same sequence, place the probe in the
test cavity opening labelled 2.0 c m
3
Note that the display looks the same as with the
0.5 cm
3
measurement except for the value placed next to the letters ECV 2.0. If you
wish, the same sequence can be followed with the 5.0 cm
3
opening on the test cavity.
To keep a record of this test cavity calibration check, simply press the print all
pushbutton on the front panel of the GSI 38.
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. Your GSI 38 is carefully
calibrated at our factory which is at approximately 250 feet above sea level. If you are
located at an elevation of 1000 feet or higher, your instrument may need to be
recalibrated to account for your elevation (See Section XXXX). If is not necessary to
recalibrate for barometric pressure changes on a daily basis. Just keep in mind that
a change in barometric pressure (i.e., from low to high or high to low) will slightly affect
the test cavity readings.
ALTITUDE ADJUSTMENT
The Altitude calibration adjustment allows the instrument operator to “correct” the ear
canal volume (ECV) measurement and test cavity volume measurement
for variations
due to altitude. Because the GSI 38 is a pressure-sensitive device which makes
measurements relative to ambient air pressure, changes in air pressure due to weather
or altitude will affect the ECV read-out of the instrument. The slight pressure change
resulting from changing weather conditions will usually yield volume read-outs within
+/- 0.1
of the expected cavity value, but pressure changes due to altitude can shift
these cavity values by as much as 30%. These changes in pressure do not affect
the accuracy of the compliance measurement system in any way. However, many
instrument operators prefer that their equipment give ECV values as they would appear
at sea level. The altitude calibration mode allow the operator to adjust his/her Auto
Tymp without the services of a qualified GSI representative.
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