Zeiss humphrey HFA II-i series, Field Service Manual

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Humphrey Field Analyzer II - i Appendix I
Confidential and Proprietary
52235C1105 I - 3
Field Service Guide
Calibration Shift Worksheet - After Service
This worksheet (called the Calibration Shift Worksheet) enables the service engineer to determine if
there has been a shift or change in instrument light intensity calibration. The worksheet compares
the
Before
light intensity data to the
After
light intensity data. The worksheet should be used anytime
recalibration of the white light intensity has been performed.
NOTE: There may be instances when the Before light intensity data cannot be obtained. In these cases, the
worksheet cannot be completed and therefore is not required.
The lower portion of this Worksheet enables the service representative to determine the significance
of the light intensity shift, and whether or not the doctor or office manager should receive a copy of
the calibration notice. If the shift is determined to be significant, it is important that the doctor is
aware of the shift for future patient diagnosis.
Worksheet
dB ratio = 10*Log(BKGD
FtL
/ #37
FtL
)
Note: #37 is the same Ft-L value as the 29 dB data point on the White Light Verification Printout.
1. Using above formula & values from the BEFORE White Light Verification Data Printout,
find the OLD dB ratio: dB
2. Using above formula & values from the AFTER White Light Verification Data Printout,
find the NEW dB ratio: dB
3. Find the dB shift: dB
(OLD dB RATIO) – (NEW dB RATIO) = dB shift
Do you need to leave the calibration notice?
1. If dB shift is +/- 1dB, DO NOT leave the notice.
2. DO NOT include (+) or (–) signs on the notice.
3. If dB shift is (+), circle low on the notice.
4. If dB shift is (–), circle high on the notice.
5. If ±1dB or greater shift, leave the cal notice.
6. If ±4dB or greater shift, call your regional manager.