TM 9-6140-200-14
b. Optical Tester Maintenance.
(1) After each use, clean and dry all tester parts.
(2) Keep the plastic cover and measuring window of the tester thoroughly
cleaned and dried. This will insure a clear view of the tester scale and
rectangle during battery testing.
(3) Optical Tester Accuracy check.
Here's how to test the tester.
a. Take a reading using distilled water (Item 6, Appx C).
b. If reading is more than 34 degrees F or less than 30 degrees F, your
tester needs adjusting. Take three (3) or four (4) readings to be sure.
c. If a reading is off, remove the instruction plate on the bottom by working a
knife under the edge.
d. Carefully dig out the sealer over the screws closest to each end.
e. The screw farthest from the eyepiece controls the 32 degree Fahrenheit
end of the scale. Use a small screwdriver to adjust the screw. Clockwise
increase the reading; counterclockwise reduces it. Make sure the final
adjustment to 32 degrees Fahrenheit is clockwise (See Figure 3-4).
f. Now check the minus side of the scale. Mix up a solution of exactly one
part distilled water and one part anti-freeze. (stir well). Take several
readings with the anti-freeze solution. If reading is more than - 32 degrees
Fahrenheit or less than -36 degrees, adjust to -34 degrees Fahrenheit.
Figure 3-4
3-10
