Application
CPM 280 is a compact pocket meter for
measuring pH value and redox potential.
CPM 280 is suitable for pH and redox
measurement in the following fields of
application:
? Wastewater treatment plants
? Drinking and surface water
? Laboratory and field measurement 

Measuring principle pH measurement
The pH value is used as a unit of measurement for the acidity or alkalinity of a liquid medium.
The membrane glass of the electrode supplies an electrochemical potential which is dependent
upon the pH value of the medium. This potential is generated by the selective penetration of
H+
ions through the outer layer of the membrane. An electrochemical boundary layer with an
electric potential forms at this point. An integrated Ag/AgCl reference system serves as reference
electrode.
The transmitter converts the measured voltage into the corresponding pH value using the Nernst
equation.
Redox measurement
The redox potential is a unit of measurement for the state of equilibria between oxidising and
reducing components of a medium. Redox potential is measured similarly to the pH value.
A platinum or gold electrode is used instead of pH-sensitive membrane glass. Analog to the
pH measurement, an integrated Ag/AgCl reference system is used as a reference electrode.
Measuring system A complete measuring system comprises:
? CPM 280 pocket meter
? Norylab CPS 51 pH combination electrode with built-in NTC 30 temperature sensor,
1.5 m (4.9 ft) fixed cable and a water-proof DIN plug
? plastic bowl 50 ml for sampling
? stand used as electrode holder
Input
Measured variables pH, redox, temperature
Measuring ranges
Input impedance > 1 x 10
12
? (at nominal operating conditions)
Input current < 1 x 10
–12
A (at nominal operating conditions)
Power supply
Sensor connection via fixed cable
Supply voltage
pH –2.00 ... 16.00
Redox –1999 ... +1999 mV
Temperature –5 ... 80 °C (23 ... 176 °F)
Batteries 4 x 1,5 V alkali-manganese batteries, type AA
Service life approx. 3000 h