Thermo Fisher Scientific ECFP21A1A1 Differential pH Sensor - Manual (Page 14)

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4.2.4
Slowly fill the reservoir with 7pH Standard Cell Filling Solution so the solution just covers
the reference O-ring.
Do not over fill. 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)
4.2.6 After replacing the salt bridge and reference solution, calibrate the sensor according to the
instructions in the Alpha pH2000D 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.
4.3 pH Sensor Troubleshooting
General Inspection
If the sensor is not providing reasonable signals to the analyzer, check the following:
1. Inspect the integrity of the glass electrodes. If the electrode is broken, replace the sensor.
2. Inspect the integrity of the salt bridge junctions. Be sure that they are clean and moist. If the salt
bridge has been allowed to dry out it may be necessary to replace the salt bridge and filling
solution.
3. Inspect the sensor cable for damage to the outer jacket. Any cuts or kinks may damage signal
connections.
4. Inspect terminal block connections to be sure wires are not corroded or loose.
5. Make sure all sensor wires are connected to the correct places on the analyzer terminal block.
Depending on the analyzer, some terminal block jumpers may be required and it is common to
put those jumpers in the wrong place.
6. The sensor electrodes should be immersed in a solution of known pH.
7. Establish that the analyzer electronics are working correctly by verifying operation with another
sensor.
Note: Any new sensor that has been in storage for more than a few days should be soaked in tap water or
a solution of known pH for at least 30 minutes to before reviewing the span and offset performance.
Note: The electrodes of any pH sensor in storage must be kept moist at all times. Protective caps should
be filled with storage solution for best performance. The protective cap should be placed securely over
the sensor head.
If the sensor passes the general inspection, there are four basic tests that can verify the temperature
measurement, the pH offset, the pH Span and the pH span on sensor power. If the sensor passes these
tests it should be ready for service.