Vaisala K-PATENTS PR-23 Series, Instruction Manual, Page: 71 / 246

7 Regular maintenance 61
7 Regular maintenance
The need for regular maintenance is minimal, due to the construction with no moving
parts, no mechanical adjustementsand with a solid-state light source. The following
rules apply:
– Keep the sensor head and the Indicating transmitter clean and dry.
– Check that the ambient temperature is not above +45 °C (113 °F). The sensor head
should not be too hot to keep a hand on.
– If your refractometer has prism wash, check that it works, see Section 5.1.3.
– Follow preventive maintenance program, if any.
7.1 Checking the sensor humidity level
The PR-23 sensor head has an internal humidity detector. The humidity reading can
be checked on the Indicating transmitter display, select
3 SENSOR STATUS
from the Main
menu. Check the humidity reading once in every three months.
Increasing humidity level indicates either condensate forming in the sensor head (if
the process temperature is below ambient) or prism leakage. If the humidity reading
exceeds 30 %, replace the dryer. If the reading exceeds 50 %, check the prism seals.
Relative humidity exceeding 60 % will produce a diagnostic message
HIGH SENSOR
HUMIDITY (see Section 8.1.7). Contact service if internal humidity increases.
7.2 Checking the prism and prism gaskets
Once a year check that the prism surface is smooth and clean and free of erosion and
small holes or digs. If the prism is scratched, eroded, or the gaskets seem to leak,
contact service.
Important: In 3-A certified sensors , prism gasket replacement and other repairs
must be done by authorized Vaisala K-PATENTS
®
service centers only . If gaskets
of 3-A certified sensors are replaced in the field, the certification is no more valid.