7
Troubleshooting
Fault
Possible cause
Remedy
Sensor cannot be cali‐
brated – display on meas‐
uring device / controller
higher than DPD-1 meas‐
urement
Run-in time too short
Refer to """Run-in time"""
Membrane cap damaged
Replace membrane cap;
allow sensor to run in,
calibrate
Troublesome substances in the water
Check water for trouble‐
some substances and
remedy this
Short circuit in the measuring line
Identify short circuit and
eliminate the cause
DPD chemicals out of date
User new chemicals,
repeat calibration
pH value < pH 5.5
Increase pH value (pH
5.5-8.0)
Sensor cannot be cali‐
brated – display on meas‐
uring device / controller
lower than DPD-1 meas‐
urement
Run-in time too short
Refer to """Run-in time"""
Coating on the membrane cap
Remove coating - refer to
"""Maintenance""",
replace membrane cap;
allow sensor to run in,
calibrate
Sample water flow rate too low
Correct flow rate
Air bubbles on the outside of the mem‐
brane
Remove air bubbles by
tapping and increase flow
rate if necessary
Troubleshooting
44
