Fluke Biomedical 07-443 - Manual (Page 11)

Maintenance/ Calibration
Calibration Check
3
3-1
Section 3
Maintenance/ Calibration
3.1 Calibration Check
It is a good practice to perform a calibration check on the Densitometer at least once every two (2) weeks,
(more or less depending on the frequency of use of the unit). Use the following procedure:
1. Zero the instrument (refer to Section 3 -Operation).
2. Place step # 4 of the supplied precision step wedge over the aperture.
3. With the wedge in position, gently close the top section of the unit until the Photo Head and the
Aperture are pressed lightly against the wedge.
4. Press the READ button. The measured density will be displayed.
5. Slowly allow the top section of the unit to return to the open position.
6. Remove the step wedge.
7. Compare the density displayed in step 4 to the stated density on the step wedge.
8. Using a screwdriver, adjust the potentiometer (accessible from the right hand side of the top section
of the unit) until the reading displayed matches the stated density.
9. Press the READ button and wait for a reading. Repeat for each change in the calibration
potentiometer.
3.2 Step Table Accuracy
For quality control purposes, the calibration of the instrument with the supplied step tablet is sufficient.
However, it should be noted that the slope of the indicated density curve will change if any color shifts are
caused by the materials being measured. Although the light source is close to the ANSI standard of
typical response of the human eye, it is not exact. Therefore, films that produce a spectral shift may
produce consistently higher or lower density readings. In such cases, a calibrated step wedge of the
same material as being measured is necessary to adjust instrument calibration.