Introduction; Conductivity Measurement - Hach POLYMETRON 9125 Operator's Manual

Transmitter 9125 – Conductivity / resistivity measurement

Introduction

Conductivity measurement

Page 4
The 9125 transmitter is a user-friendly instrument
(installation, programming),
microprocessor it can be configured to correspond to
any application in the following sectors :
drinking water,
waste water,
process (chemistry, paper mills, sugar mills...),
measurement in pure/ultrapure water (energy
power plants, semiconductor industry, chemistry).
The 9125 transmitter should be connected to a probe
via a cable.
The electric conductivity measures the transport of
electric charges in any field. In metal conductors, the
current flows by transport of electrons, whereas in
solutions, it flows by transport of ions such as Na+ and
Cl- which ensure the transport of charges. The higher
the transport of charges is, the greater is the
conductance of the solution.
Conductivity is the capacity a solution has to
conduct current.
In solution, conductivity is much more complicated
than in conductors because several species ensure
the transport of charges. For instance, in drinking
water the conductive species registered are sodium,
calcium, magnesium,
phosphates and nitrate ions. For slightly concentrated
solutions, the concentration of H
-
OH ions (stemming from the weak dissociation of the
+ -
water [H ] = [OH ] = 10
longer be neglected in the presence of the product,
this therefore leads
Conductivity/Concentration.
equipped with
ferrous cations, ferrites,
+
protons and hydroxyl
-7
mol/l to 25°C) can no
to a non-linear variation
a