Pr
o
Minent
®
Page 32
Sensor:
Troubleshooting
Free Chlorine
Fault
The sensor
cannot be
calibrated -
measuring
device/
controller
display value is
greater
than
DPD-1
measurement
The sensor
cannot be
calibrated -
measuring
device/
controller
display value is
smaller
than
DPD-1
measurement
Measured
variable value
is “zero”
Measured
variable display
unstable
Possible cause
Run-in period too short
Membrane cap damaged
Interference from water
contaminants
Short circuit in signal cable
DPD-chemicals spent
pH-value < pH 5.5
Run-in period too short
Membrane cap deposits
Sample water fl ow inadequate
Air bubbles on the outside of the
membrane
Surfactants in water (membrane
is transparent!)
pH-value > pH 8.0
No electrolyte in membrane cap
Electrolyte displaced by gas
bubbles in the sample water
Only bound chlorine present
Chlorine content below the lower
measuring range limit
Sensor incorrectly connected to
controller
Run-in period inadequate
Sensor defective
Air bubbles on the outside of the
membrane
Membrane damaged
Cause lies with the controller
Remedy
See “Run-in period”
Replace membrane cap.
Allow sensor to run in, calibrate
Identify interfering contaminant
and implement remedy
Identify short circuit and repair
Use new DPD chemicals, repeat
calibration
Increase pH-value (pH 5.5-8.0)
See “Run-in period”
Remove deposits (see “Main te-
nance”). Replace membrane
cap. Run-in sensor, calibrate
Adjust fl ow rate
Tap to remove air bubbles and
in crease fl ow if necessary
Remove surfactants and replace
membrane cap, run in sensor
and recalibrate. If necessary
use CDP sensor
Lower pH-value (pH 5.5-8.0)
Fill in new electrolyte (see
“Assembly”, “Run-in period”
and “Calibration”)
Consult ProMinent
If chloramine is present (DPD-4
test), replace water or chlorinate
Add chlorine and then repeat
calibration or use appropriate
sensor
Connect sensor correctly to
controller
Run in for at least 3 h
Replace sensor
Tap to remove air bubbles and
increase fl ow if necessary
Replace membrane cap. Run-in
sensor, calibrate
Identify cause and remedy
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24.02.2009 11:56:04 Uhr
24.02.2009 11:56:04 Uhr