Xylem FDO 925 - Manual (Page 11)

FDO
®
925 Maintenance, cleaning, replacement
27 ba75898s01 04/2010
3.3 Cleaning the sensor
3.3.1 Exterior cleaning
Dirt on the sensor can affect the measuring characteristics. Biological depos-
its for example, consume oxygen and can, when occurring on the sensor
membrane, impair the responding behavior and cause values that are too
low. Therefore, we recommend regular visual inspections and exterior clean-
ing as necessary.
Pay attention to the following points for cleaning:
z First, thoroughly rinse the sensor with tapwater to remove loosely adher-
ing dirt.
z Rough dirt on the sensor shaft can be brushed off with a soft brush. Atten-
tion: Do not use the brush in the area of the sensor membrane. Risk of
damage!
z The sensor cap including the sensor membrane should be wiped with a
soft and moist microfiber cloth.
z In the case of persisting dirt you can add some household washing-up liq-
uid to the tapwater. Attention: Never use any alcohol for cleaning!
3.3.2 Interior cleaning of sensor cap and sensor head
If moisture or dirt have penetrated under the sensor cap, e.g. because the
sensor cap is damaged, you can make the sensor ready for operation again
as follows:
CAUTION
Only use nonabrasive, alcohol-free detergents, as otherwise the optical
surfaces could be damaged.
1 Remove the sensor cap (see section 3.2).
2 Clean the sensor head and sensor cap:
– Rinse all inner surfaces with tapwater
– Remove contamination containing fat and oil with warm water and
household washing-up liquid
– Then rinse all inner surfaces with deionized water
3 Pat dry all surfaces with a clean, lint free cloth.
4 Allow the sensor and sensor cap to dry completely at a dry location
so moisture can evaporate even from corners difficult to access.
When doing, so protect the inside of the sensor cap from light.
5 Put the sensor cap on (see section 3.2).