Zeiss humphrey HFA II-i series Field Service Manual page 464

Instrument: Humphrey Field Analyzer II-i
Subject: Calibration Changes with Revision 4.1 or Greater
Software
Status: Informational
Introduction
This service bulletin introduces changes to the HFA II-i calibration. Two new startup tests have been
added with the release of software revision 4.1. These tests become active once the software has been
loaded, and the instrument has been powered On. The first test evaluates the position of the shutter; the
second test performs an evaluation of the aperture position.
Shutter Misalignment Test
At startup of the instrument, an evaluation of correct shutter positioning occurs. The instrument makes a
measurement, with the shutter in place, and determines the light intensity that has passed around the
shutter paddle. The passed light is compared against a limit. Failure of the test will result in a Startup
State Error 18 error, "Shutter may be misaligned." Pressing Proceed will not allow testing. Failure of the
shutter alignment test will require normal shutter calibration.
Aperture Spot Ratio Test
The spot ratio test measures the spot intensity ratio between spot sizes V and III. The spot ratio is
determined and compared with a theoretical value of 16. If the spot ratio is not within the specifications
(two dB or 58% of the expected value), a Startup State Error 19 error, "Aperture may be misaligned"
results. Pressing Proceed will not allow testing. Failure of the spot ratio test will require the aperture
calibration, followed by measuring and saving a spot ratio value that is within specification. The
procedure is described in this bulletin.
During the first calibration of the instrument, once revision 4.1 software has been loaded, a tighter
specification (26% of the expected value) for the spot intensity ratio test is implemented. Failure of the
spot ratio test any time after a calibration has been completed will require the aperture calibration,
followed by measuring and saving a spot ratio value that is within specification.
Measuring and Saving the Aperture Spot Ratio
In the aperture calibration menu, additional information to view and measure the aperture spot ratio is
provided. The screen contains the following information:
V/III Spot Ratio
Stored
XX.XX (14.1 – 17.9)
Measured
•
XX.XX represents the stored value of the V/III spot ratio.
•
(14.1 – 17.9) represents the allowable range of the spot ratio.
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This bulletin replaces Service Bulletin FA2i-031
PROPRIETARY and CONFIDENTIAL
SERVICE
BULLETIN
No.: FA2i-031A
Date: 15 Feb 08
Pages: 2
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