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To keep a record of this test cavity calibration check, press the Print All button
on the front
panel of the instrument.
Altitude Adjustment
The altitude calibration adjustment
enables a “correction” to
the ear canal volume (ECV)
measurement and test cavity volume measurement for variations due to altitude. The instrument is a
pressure sensitive device that makes measurements relative to ambient air pressure. Changes in air
pressure due to weather or altitude will affect the ECV readout of the instrument. The slight pressure
change resulting from changing weather conditions will usually yield volume readouts with ± 0.1 cm
3
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, it will affect the ECV values. The altitude calibration mode allows
adjustment of the Auto Tymp without the services of a qualified GSI representative.
226 Hz Probe
1000 Hz Probe
Altitude in Feet
Equivalent 2.0 cc
Reading
Altitude in Feet
mmho Reading
0
2.0 ±0.1
0
8.85 mmho ±0.44
1000
2.1 ±0.1
1000
9.20 mmho ±0.46
2000
2.2 ±0.1
2000
9.56 mmho ±0.48
3000
2.2 ±0.1
3000
9.91 mmho ±0.50
4000
2.3 ±0.1
4000
10.3 mmho ±0.52
5000
2.4 ±0.1
5000
10.6 mmho ±0.53
6000
2.5 ±0.1
6000
11.1 mmho ±0.56
7000
2.6 ±0.1
7000
11.5 mmho ±0.58
8000
2.7 ±0.1
8000
12 mmho ±0.60
9000
2.8 ±0.1
9000
12.4 mmho ±0.62
10000
2.9 ±0.1
10000
12.8 mmho ±0.64
226 Hz Probe Tone Altitude
1000 Hz Probe Tone Altitude
Correction
Correction
NOTE:
Operation of the system at an altitude of 10,000 feet may affect the ability to pressurize to the
maximum 5.00 cm
3
.
To enter altitude calibration, press
, and
simultaneously. The LCD will now display
the Settings Main Menu. When entering the Settings Main Menu, the display will read as follows:
Altitude - user check
Cal modes
Page modes
