wtw FDO 925 - Checking the Zero Point of the Sensor

FDO
®
925 Maintenance, cleaning, replacement
13
ba75898e06 08/2015
3.4 Checking the zero point of the sensor
There are two methods to check the zero point of the sensor:
 Measurement in a nitrogen atmosphere (recommended method)
 Measurement in a sodium sulfite solution according to DIN EN 25814/
ISO 5814.
Test criterion The sensor is OK if the measuring instrument displays < 0.5 % D.O. satura-
tion after 15 minutes.
If the sensor cap is visibly damaged it has to be replaced.