9 Carrying out maintenance work
The maintenance interval of the OTT PLS 500 strongly depends on the local ambi-
ent conditions. Even a thin build-up of deposits on the measuring cell will not
appreciably affect the measurement results. If very heavy contamination occurs at
the station due to algae, mud, vegetation or sediment, the pressure probe should
be checked from time to time. For example, imprecise or implausible measured
values may indicate a "blocked" measuring cell.
Maintenance plan
▶
recommended interval: every 15 months (adapt to local environmental condi-
tions if necessary)
▶
work required:
– check pressure sensitive membrane of the pressure
cell; clean if necessary
– check the desiccant of the humidity absorber;
replace if necessary (see seaparate operating
instructions for the humidity absorber used)
Check/replace desiccant of the humidity absorber
Required replacement parts
▶
Dry desiccant cartridge for replacement (color indicator
➝
orange
■
)
For procedure, see separate OTT FAD 4 and OTT FAD 6 assembly instructions.
Please note:
With a correctly installed and regularly maintained humidity
absorber, the relative humidity in the probe housing is always below 25 %
(see Chapter 7.2,
<value1>
in the response to
aD0!
after
aV!
).
If the humidity rises above this, the OTT PLS 500 outputs error message
+64
in
the device status (
<value9>
in response to
aD2!
after
aV!
). This is usually an
indication of an insufficiently maintained moisture absorber. Slightly increased
values allow further operation of the pressure probe. In this case, however, error-
free measured values can no longer be guaranteed over the entire operating tem-
perature range. When the dew point is reached, drops often form in the pressure
compensation capillary, resulting in unusable measured values! If this occurs, the
OTT PLS 500 must be replaced.
46