eutech-instruments alpha ph differential probe User Manual

Instruction 

manuals 

 

         ECFP21A1A1 

 

 

 

14

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. 

 

Temperature Span 
Disconnect the BLACK and YELLOW sensor wires from the analyzer.  Use an ohmmeter to measure the 

resistance between the BLACK and YELLOW wires.  The meter should measure a resistance corresponding 
to the sensor temperature as outlined in the following table.   

 

Sensor 

Temperature 

5C  15C 25C 35C 45C 

Thermistor Resistance 

630 Ω 430 

Ω 300 

Ω 215 

Ω 155 

Ω 

 

If the measured resistance is within 10 to 20 ohms of the expected value, the element should be satisfactory.  
If not, please consult the factory.