Zeiss humphrey HFA II-i series Field Service Manual page 164

Troubleshooting
Step 8 Sets bowl illumination to calibration value
Turns the bowl "on" to the specified calibration value (previously at full intensity).
Step 9 Initializes the DVM
Sets the DVM to internal bipolar mode, then initiates the hardware auto-cal sequence. Sets
DVM to bipolar internal mode, then reads for zero value. Iterates until reasonable zero is
attained.
Step 10 Zeros the DVM
Sets the DVM to external unipolar, then initiates the hardware auto-cal sequence. Sets DVM
to (unipolar) detector mode, then reads for zero value. Iterates until reasonable zero is
attained.
Step 11 Turns on the projection lamp as a secondary output check.
Step 12 Positions motors to bowl origin
Sets the X, Y, and F motors to point to the center of the bowl.
Step 13 Sets aperture wheels to clear, w/Goldmann V
Simultaneously moves both wheels to their maximum apertures.
Step 14 Turns projector on
The projector is turned on with the output voltage associated with its calibrated 10,000 asb
level.
Step 15 Sets voltage level
The projector turret is positioned 35 degrees above center. The shutter is opened, with no
attenuation, and intensity is read. The intensity is compared with the value established at
calibration time. If there is a notable difference, the output voltage is adjusted until the
intensity read is within a specified limit of the calibration value. The voltage drop across the
projection lamp is then measured and used as a reference for future voltage adjustments.
The shutter is then closed.
Step 16 Sets flash duration
The shutter is set to flash for a 200-millisecond duration.
Step 17 Verifies wedges
At 10 points on each wheel, the intensity is measured and compared against the value stored
in memory. If any value is greater than 1 dB from the measured value, the test fails. If the
RMS value for these readings is greater than 0.5 dB, the test fails.
Step 18 Turns off projector
The projector is turned off, but the background bowl lamps are left at their established
values.
Field Service Guide
Humphrey Field Analyzer II - i
Confidential and Proprietary
5 - 14 52235C1105