Thermo Scientific AquaSensors
™
AnalogPlus
™
Differential pH Sensor User Guide
25
4.2.
pH Sensor Refurbishment - Replacing the Salt Bridge and Reference Solution
4.2.1.
If the sensor head has been cleaned
(see
section 4.1.2) and calibration cannot be
achieved, replace the salt bridge and
reference solution.
4.2.2.
Hold the sensor firmly with the electrode tip
facing upwards. Remove the existing salt
bridge by using a 15/16 wrench (24mm)
and turning it counterclockwise. Dispose of
the salt bridge using an approved method.
4.2.3.
Pour out the old reference solution. Rinse
the reservoir with distilled or de-ionized
water.
4.2.4.
Slowly fill the reservoir with 7pH
Standard Cell Solution so the
solution just covers the reference
O-ring.
Do not overfill.
Overfilling will
lead to excessive pressures that
will affect the junction potentials of
the reference.
4.2.5.
Slowly screw the new salt bridge clockwise onto
the sensor head until secure. Tighten the salt
bridge with a 15/16 wrench (24mm) until snug.
Do not over tighten.
Maximum torque: 10 lbs
⋅
in (1.13 N
⋅
m)
Figure 4.1:
Replacing the salt bridge
and reference solution
4.2.6.
After replacing the salt bridge and reference
solution, calibrate the sensor according to the
instructions in the controller manual.
If after cleaning and refurbishment sensors still have slow responses, low measurement
slopes or are seriously abraded or scratched, they must be replaced. Contact your local
representative or call Thermo Fisher Scientific Customer Service.
