Xylem FDO 925/STM, Руководство по эксплуатации, Страница: 9 / 11

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Checking the zero point of the sensor 3.4
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.
saturation after 15 minutes.
4 What to do if ...
Error symptom Cause Remedy
No temperature value or
D.O. value

No connection between meter and
D.O. sensor

Establish connection between
meter and D.O. sensor

Cable defective

Return the D.O. sensor
Measured value too high
or too low or error
message:
Error

Coating on sensor cap

Clean the outside of the sensor
(

chapter 3.3.1)

Membrane damaged

Exchange the sensor cap

Service life of the sensor cap over

Check the sensor

Replace the sensor cap as
necessary (

Chapter 3.2)

Dirt inside the sensor cap and
sensor head.

Protective hood not properly
tightened.

Sensor cap untight or defective.

Dismantle the sensor cap

Clean the insides of the sensor cap
and sensor head (

Chapter
3.3.2)

Mount the sensor cap correctly and
tighten the protective hood as far
as it will go (

Chapter 3.2)

Replace a defective sensor cap as
Incorrect temperature
display 
The temperature sensor is not
immersed deep enough in the
measuring solution

Observe the minimum immersion
depth

Temperature sensor defective

Return the D.O. sensor
Error message: no cap

No sensor cap put on

Clean the sensor head and sensor
cap

Sensor cap not recognized

Return the D.O. sensor

Sensor cap defective

Replace the sensor cap