Fluke Biomedical 07-440 - Manual (Page 12)

Nuclear Associates 07-440
Operators Manual
3-2
Periodically check the alignment of the aperture and the photohead, especially if the instrument has been
dropped. Inherent mechanical design makes this alignment check easy:
a. Remove the aperture in use.
b. Press down on the measurement arm.
c. Check that the o-ring light seal fits exactly into the depression normally occupied by the
aperture.
If the arm is out of alignment, perform the
procedure outlined in Aperture Alignment.
If the instrument is used to measure halftones:
a. The 3 mm aperture should be used to reduce the effect of the sampling area.
b. Take into consideration the effects of the maximum density of silver in the dots and fringes around
the dots.
c. Avoid comparing a soft-edged dot film with a hard-edged dot film.
3.2 Aperture Alignment
The aperture alignment should be checked, as described earlier in this Section, at least once a year.
Correct any noted misalignment using the following procedure:
1. Unplug the power cord.
2. Remove the top rear cover by taking out the four (4) screws securing it to the base.
3. Using a 5/32 inch (4 mm) Alien hex wrench, loosen the three (3) screws at the rear of the arm
spring, one complete turn. DO NOT LOOSEN THE THREE (3) SCREWS ON THE ARM ITSELF.
4. Inspect the o-ring for damage. If damage is evident, replace it.
5. Push the arm down, with the aperture removed, until the o-ring is exactly centered in the aperture
holder.
6. Tighten the three (3) spacing screws, alternately, a quarter turn at a time, until they are fast, while
still holding the arm down.
7. The arm should now be exactly aligned.
3.3 Calibration
A calibrated quality control step tablet, P/N 07-440-100, is supplied with the instrument at the time of
shipment. This tablet has been factory calibrated with the instrument. Although it is calibrated with high
accuracy, its primary use is to check for any drift in the instrument supplied with it. To check long term
precision of the instrument, the step tablet should be used at least monthly according to the directions on
the envelope.
If the instrument is to be calibrated using another standard calibration step tablet, the following
considerations should be taken into account:
1. Use a 3 mm aperture and plot indicated readings versus readings on the calibration sheet supplied
with the tablet the slope of this line should be exactly 1.00.
NOTE