thoroughly in demineralized water and the outside wiped dry.
filter wedge containing the light filters can best be cleaned by
wiping both surfaces with a soft tissue dampened with isopropyl
(2) If the instrument is to be placed in storage for a signifi-
cant length of time, the batteries should be removed to avoid damage
that may result from battery leakage.
Avoid exposing the variable
interference light filter to heavy moisture for extended periods of
See Chapter 3 for Operator Maintenance and Preventative Main-
tenance Checks and Services.
Sample Cell Matching.
Although the sample cells furnished with
the spectrophotometer are essentially distortion free optically,
nicks and scratches acquired during handling can cause a mismatch
between two sample cells and thus introduce error in the test results.
This type of error can be minimized by optically matching the sample
The following procedure tells how.
If the sample cannot be
matched within +0.5%T, one or both cells should be discarded.
(1) Set the instrument light switch in the ON position and
allow approximately 2 minutes warm-up.
(2) Insert the % Transmittance-Absorbance Meter scale in the
meter and adjust the Wavelength Dial for 510 nm.
(3) Place the light switch in the ZERO CHECK position and adjust
the Zero Adjust Control for a reading of 0% transmittance.
light switch to the ON position.
(4) Pour exactly 25 ml of demineralized water into each of two
clean sample cells.
(5) Place one sample cell in the instrument cell holder and ad-
just the Light Control for a reading of 95% transmittance.
(6) Place the other sample cell in the cell holder and, note the
direction and amount of deviation from the 95% value.
(7) Try to acheive a match within +0.5%T. Rotate the cells 180°
and recheck the match.