Calibrating a 331C, 341C
How to Properly calibrate a 331C and 341C for accurate Density readingsWhen the instrument is first turned on it must be nulled (zeroed) before taking measurements. To perform this task proceed as follows:
Nulling the instrument
- Turn on the instrument.
2. Close the unit with no film (read air).
3. Press and hold the "NULL" button. While holding down the "NULL" button, press and hold the "Measure" buttons until the lamp goes out (3 to 4 seconds). You may then release both buttons.
3. Press and hold the "NULL" button. While holding down the "NULL" button, press and hold the "Measure" buttons until the lamp goes out (3 to 4 seconds). You may then release both buttons.
4. A second reading should be taken with no film to verify that the unit did indeed null (it should read zero with no film).
*Once the unit is reading 0.00 without any film the "NULL" button should NOT be used again until the unit is turned off.
Calibrating / Setting the instrument's slope
- Locate the supplied Calibration Reference film and the small screwdriver.
2. Turn on and null the instrument as described above.
3. Measure the CAL step(4) of the supplied film.
4. If the measurement differs from the certified value by more than ±0.02D then use the small screwdriver to increase or decrease the unit's slope.
5. Once the Cal step is in agreement read the additional steps to see if you have a Linear unit. They should now hold the +/-0.02 tolerance to the strip.
NOTE: When measuring density values above 2.50D, care should be taken that the reading head light seal is completely on the surface of the film being measured. Always measure density with the film emulsion side up.
If the unit does not read zero after several attempts at nulling, and the light source and power supply have been verified; there is an internal failure and the unit must be returned for repair. It is recommended that the calibration / verification be performed once a week. More frequent verification can be performed if required by local regulations.
