Metrohm 827 pH lab - Manual (Page 52)

8.1 Troubleshooting
44
826/827 pH meter, Instructions for Use
Problem Possible cause Remedy
Measuring signal absent
or very variable Electrode not connected • Connect electrode
Air in or in front of the diaph-
ragm • Remove air
Faulty electrode • Replace electrode
Measured value remains
unstable and does not
fulfill drift criterion Dirty glass membrane or diaph-
ragm • Clean membrane or diaphragm
pH or temperature of the solu-
tion is not stable • Measure under exclusion of air
• Thermostat the solution
Unsuitable electrode:
• Conductivity too low
• Organic solution
• Use suitable electrode
Electrode not connected • Connect electrode
Faulty electrode • Replace electrode
Slow adjustment of
measured value Dirty glass membrane or diaph-
ragm • Clean membrane or diaphragm
Slope too small on cali-
bration Dirty glass membrane or diaph-
ragm • Clean membrane or diaphragm
Glass membrane deswollen af-
ter measurement in non-
aqueous solution • Immerse electrode in water between
measurements
Poor buffer solutions • Replace buffers
Old Electrode • Replace electrode
Measured value obvious-
ly incorrect Incorrect calibration • Check / Repeat calibration
• Check / Replace buffers
Manual temperature input incor-
rect • Enter correct temperature of the solu-
tion
Dirty glass membrane or diaph-
ragm • Clean membrane or diaphragm
Electrolyte or electrode too old • Refill electrolyte or replace electrode
Faulty electrode • Replace electrode