How to troubleshoot a pH measurement problem?

calibration

#1

Troubleshooting techniques for pH measurement.

1.Measuring electrode can be bad.

Glass electrodes age with time,causing a slowed reaction to pH change.

Glass electrode can be broken or have small holes in them,usually causing a reading to go “off scale”.

Glass electrodes can be coated very easily,which causes potential error as the coating builds.

Glass electrode can be etched by fast flows where heavy particles are present or by hydroflouric acid at low pH level.

2.Reference electrode may not be working

Reference junction can be clogged.
Reference electrolyte may be incompatible with the chemistry of the process.
Reference electrolyte may have dried up
Reference electrolyte may be depleted
Pressure in process may cause process water to replace electrolyte

3.General pH problems

Probe may be mounted incorrectly
-Flow problems
-Air bubbles
-Sediment
-Coating
-Dead-leg of pipe
-Stagnant area of tank
-Pressure limitation
-Temperature limitation
-High purity water problems

4.Fouling of measuring electrode

Clean with diluted HCI and water

5.Cracked electrode

Continuous reading of 7 pH

6.Fouling of reference electrode

-Immerse in boiling water
-Increase flow of electrolyte