Welch Allyn GSI 38, Service Manual

Page: 47 / 96

The calibration of compliance measuring devices is affected by air density. As
the air gets thinner, the volume measurement in a hardwall cavity increases.
Therefore, as you go up in altitude, barometric pressure decreases making the
hardwall cavity appear larger than it is. The GSI 38 allows the flexibility to
display the real altitude effect or to correct the ear canal measurements relative
to sea level.
A)
If the customer prefers to correct the ear canal volumes relative to sea
level then adjust
Keys until the cm3 XXX value equals
2.00 After adjusting to the desired level store the value by pressing
the Key. The display will start “flashing” indicating that the
compliance calibration process is complete.
B)
If the customer prefers uncorrected ear canal volumes (actual at altitude
measurements) then adjust the Hz Keys until the cm’ XXX
value indicates the appropriate volume measurement for the customer site
elevation according to the following altitude table.
Altitude Barometric Pressure Expected Volume Reading Calibration Volume
(ft)
(mm Hg)
at Altitude (cc)
at
Altitude
(cc)
0
759.97
2.00
500
746.51 2.01
1000 733.04 2.03
1500 719.84 2.05
2000 706.63 2.07
2500 693.93 2.09
3000 681.23 2.11
3500 668.78 2.13
4000 656.34 2.15
4500 644.40 2.17
5000 632.46 2.20
5500 620.78 2.22
6000 609.09 2.25
6500 598.00 2.27
7000 588.00 2.30
7500 578.00 2.34
8000 568.00 2.37
8500 555.00 2.40
9000 544.00 2.44
9500 533.00 2.49
10000 522.00 2.54
Press the Key to store the customer altitude volume measurement. The
display will start “flashing” indicating that the Compliance Calibration process is
complete.
5)
Press the Key to return to the Main Calibration Mode Menu.
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