Regular Maintenance; Checking Sensor Humidity Level; Checking Prism And Prism Gaskets - Vaisala PR-23 Series User Manual

PR-23 Series User Guide

8. Regular maintenance

The need for regular maintenance is minimal, due to the construction with no moving parts,
no mechanical adjustments and 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 must
not be too hot to keep a hand on.
• If your refractometer has prism wash, check that it works, see
(page 51).
• Follow preventive maintenance program, if any.
8.1 Checking 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 % results in the diagnostic message HIGH SENSOR HUMIDITY, see
Troubleshooting messages (page
8.2 Checking 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.
CAUTION!
prism gasket replacement and other repairs. If gaskets of 3‑A certified sensors are
replaced in the field, the certification is no more valid.
84
92). Contact service if internal humidity increases.
In 3‑A certified sensors, only authorized Vaisala service centers can perform
IM-EN-PR23-E
Testing prism wash