Table of Contents
Advertisement
O
P
PERATING
RINCIPALS
The 5905/5010 BOD probe is a voltammetric (polarographic)
sensor of dissolved oxygen. An oxygen permeable membrane
covers an electrolytic cell consisting of a cathode and an
anode. This membrane acts as a diffusion barrier and an
isolation barrier preventing the fouling of the cathode surface
by impurities in the environment. The cathode is the gold
electrode, and the anode is the silver electrode which
completes the electrolytic cell and acts as a reference
electrode.
Upon entering the cell through the membrane, oxygen is
reduced at an applied potential of -0.8 V referenced to the
silver electrode. The reduction current at the cathode is
directly proportional to the partial pressure of oxygen in liquid
(expressed as %-air saturation) which is also proportional to
the concentration of dissolved oxygen (in mg/L) at a particular
temperature. Thus the same partial pressure of oxygen (%-air
saturation) in liquid gives different concentrations of dissolved
oxygen (mg/L) at different temperatures because of the
different solubilities of oxygen at different temperatures.
2
Advertisement
Table of Contents
