Vaisala DM500 - Manual (Page 116)

User's Guide ______________________________________________________________________
114 _________________________________________________________________ M210205EN-D
1. Remove the sensor cap.
2. Clean the sensor surface
1. Turn off the measuring mode; the sensor must not be
cooled.
2. Loosen the three Allen screws of the sensor cap with an
Allen key. (Note that the screws have retainers, they do
not come off completely).
3. Remove the sensor cap.
4. Take a rectangular piece of soft, clean paper tissue
(optical or clean room grade tissue). Fold it twice to
obtain a fourfold tissue and roll it diagonally into a
tight roll. Wet one end of the roll with pure ethanol or
isopropyl alcohol, firmly press the end of the paper roll
against the vertical sensor surface (in the bottom of the
hole) and clean the sensor with rotating movements.
Make another paper roll and make a final cleaning with
distilled water. Finally, dry the sensor with a dry paper
roll.
If using a cotton-wool stick, press the end of the stick
against a clean surface to have a flat tip for cleaning.
5. After cleaning, the sensor surface should look like a
clean mirror surface. There should not be any oily
stains, spots, or dust.
6. If the system has warned of hygroscopic contamination
on the sensor, it is recommended to clean the sensor 2-
4 times with distilled water before the alcohol cleaning.
The cleaning procedure with distilled water is the same
as that with ethanol.
7. Replace the sensor cap and fasten the three Allen
screws. See that the small o-ring at 2 o'clock is in place
before replacing the cap.
If the sensor is very dirty, the sensing unit can be placed to upright
position, and a small amount of cleaning liquid can be poured directly
on the sensor element instead of wetting the tissue. Otherwise the
cleaning is performed as described above, but the larger amount of
water or solvent helps remove dirt without leaving residue. Be careful
not to pour liquid into gas channel openings at 2 and 8 o'clock.