FAS622en_pH measurement

Contents
1 Basics ................................................................................................ 7
1.1 General ................................................................................................................. 7
1.2 Electrochemical pH measurement .................................................................... 9
1.2.1 pH measurement electrodes ............................................................................................. 9
2 Measurement .................................................................................. 17
2.1 Arrangement of a process measurement setup ............................................ 17
2.1.1 Electrode ......................................................................................................................... 17
2.1.2 Fittings ............................................................................................................................ 19
2.1.3 Shielded instrument cable .............................................................................................. 19
2.1.4 Transmitter/controller ...................................................................................................... 20
2.2 Commissioning the measurement setup ........................................................ 21
2.2.1 Measurement location .................................................................................................... 21
2.2.2 Measurement conditions ................................................................................................ 21
2.2.3 Installation ....................................................................................................................... 22
2.2.4 Calibration ....................................................................................................................... 23
2.2.5 Buffer solutions ............................................................................................................... 24
3 Quality assurance .......................................................................... 25
3.1 How accurate is the pH measurement? ......................................................... 25
3.2 Documentation .................................................................................................. 25
3.3 Maintenance ...................................................................................................... 27
3.3.1 Critical effects on the reference electrode ...................................................................... 30
3.3.2 Critical effects on the pH electrode ................................................................................ 31
3.4 Cleaning ............................................................................................................. 32
3.5 Calibration ......................................................................................................... 32
3.6 Storage of the electrode .................................................................................. 32
4 Applications .................................................................................... 33
4.1 Waste-water treatment plants ......................................................................... 33
4.1.1 Inlet to the plant .............................................................................................................. 34
4.1.2 Biotower .......................................................................................................................... 34
4.2 Swimming pools ............................................................................................... 35
4.3 Electroplating plants ........................................................................................ 37
4.3.1 Electroplating baths ........................................................................................................ 37
4.3.2 Decontamination ............................................................................................................. 38
4.4 Power stations .................................................................................................. 40
4.5 Drinking water supply systems ....................................................................... 41
4.6 Drinking water reservoirs ................................................................................. 42
Information pH measurement