5.
With sensors used for fish farming,
screw the sensor cap back onto the
sensor by turning it clockwise. Make
sure that you do not loosen the sensor
cap.
6.
Check the sensor’s measured values on
the air and, if need be, also in a medium
rich in oxygen. Carry out a calibration if
the measured values deviate too much.
With “Oxygen saturation” display format,
the reference value with calibration on
air saturated with water vapour is 100%.
With “Concentration” display format
(mg/l, ppm), the reference value can be
taken from the relevant tables for
oxygen saturation depending on the
water temperature.
7.3 Cleaning
Clean the sensor and recalibrate it if the meas‐
ured value shifts during operation.
Pay particular attention to the following notes in
operation:
n
Always keep the area around the optical
diaphragm of the sensor clean. A biofilm
on the diaphragm cap leads to measuring
errors.
n
Use warm soapy water to clean the dia‐
phragm if it is dirty. Use a soft sponge to
clean the diaphragm. Never use hard or
pointed objects to clean the diaphragm.
Hard or pointed objects will render the
sensor cap unusable.
7.4 Troubleshooting
The 4 ... 20 mA interface of the sensor offers
the following troubleshooting options by output‐
ting fault currents:
n
The fault current “21.5 mA” indicates a
used or missing sensor cap.
n
The fault current “3.5 mA” indicates a tem‐
perature outside the tolerance or a faulty
temperature sensor.
Maintenance and troubleshooting
23
