Vaisala HMP42 - Manual (Page 45)

HMI41 AND HMP42
M210317EN-A Operating Manual
41
9. MAINTENANCE
9.1 Changing the filter and the sensor head set
For changing the filter, unscrew the steel grid, remove the membrane filter
(see Figure 9.1) and replace it with a new one. A set of membrane filters is
delivered with the probe. Screw the steel grid back on.
NOTE
Do not use the probe without the membrane filter in
order not to damage the sensors.
Figure 9.1 Changing the filter
If the steel grid looks dirty, remove it and clean the holes e.g. with a needle.
It is recommended that the sensor head set is changed by Vaisala authorized
maintenance personnel only. However, if for some reason it is necessary to do
this yourself, be careful not to break the sensor. Unscrew the sensor head set
and mount a new set in its place. Handle the sensor head with care. Calibrate
the probe using a two-point calibration procedure (see section 5.3.2).
9.2 Chemical tolerances of the HUMICAP

MINI sensor
Long-term exposure of the HUMICAP

MINI sensor to certain chemicals and
gases may affect the characteristics of the sensor and shorten its life. The
following table gives the recommended maximum ambient concentrations of
some chemicals:
ppm (typ.)
Organic solvents 1000...10 000
Aggressive chemicals (e.g. strong acids
such as SO
2
, H
2
SO
4
, H
2
S, HCl, Cl
2
, etc.)
1...10
Weak acids 100...1000
Bases 10 000...100 000
Detailed information on allowed concentrations can be requested from Vaisala
representatives.