577 Brightness of Paper
- Use a PHOTOVOLT 577 in the HI gain position with the W Search unit and allow to stabilize for about 30 minutes before use.
- Press the B (Blue) channel on the 577.
- Zero the 577 by placing the BLACK CAVITY STANDARD over the light opening and centered so that no room light leaks under the edges. Press CHANGE and ZERO. The display will read 0.0.
- Remove the BLACK CAVITY STANDARD and place the BRIGHTNESS PLAQUE over the light opening. Press CHANGE and STD (STANDARD) on the 577. CHANGE and STD lights will be on.
- Press the A (Amber) button on the 577 to change the first number on the display to correspond to the first number on the BRIGHTNESS PLAQUE. Press the B (Blue) button to change the second number on the display to correspond to the second number on the BRIGHTNESS PLAQUE and the G (Green) button to correspond to the third number. Press STD to place these numbers in the memory. The STD light will now go out.
- If, when observing the paper sample on top of the search unit and any light is seen through the sample, place the black cavity standard over the paper sample. Alternatively, a “stack” of the paper samples can be used (if available) instead of the black cavity standard. The objective here is to see that no visible light can be seen before a brightness reading is made.
- Remove the BRIGHTNESS PLAQUE and replace with sample. The brightness value will be read on the display. Continue with sample measurements.
- It is good practice to zero the 577 frequently by placing the BLACK CAVITY STANDARD on the light opening and repeating (3) above. Although the 577 is quite stable, this will ensure that the zero value is consistent.
- It is good practice to occasionally check the BRIGHTNESS PLAQUE in the same manner as in (4) and (5) above. For instance, before and after a series of measurements.
- Measurements may be made with the search unit in the inverted position. However, the BLACK CAVITY STANDARD will still be used in the upright position unless you have a flat, black velvet zero plaque. In any event, sample and standard measurements should be made in the same position.
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