Thermo Fisher Scientific EcoScan DO 6 - Manual (Page 60)

Instruction Manual DO 6
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8 PROBE CARE AND MAINTENANCE
The DO6 probe is a galvanic measuring element which produces an output
proportional to the oxygen present in the medium in which it is placed. The
galvanic probe design lets you take measurements immediately – without the
typical 15 minute wait of other dissolved oxygen probes.
The probe consists of two parts:
• An upper part consisting of the anode, a cathode, and the dual cable.
• A lower part consisting of a pre-membraned cap, and electrolyte
solution.
Oxygen diffuses through the membrane onto the cathode, where it is
consumed. This process produces an electrical current which flows through the
cable to the meter. The electric current produced is proportional to the oxygen
that passes through the membrane and the layer of electrolyte. This makes it
possible to measure the partial pressure of oxygen in the sample at a given
temperature.
Since the DO in the sample is consumed by the cathode it is essential that a
new sample must flow past the membrane of the probe to prevent the
occurrence of false readings. The probe uses very little oxygen for its
measurement. This enables it to function correctly with liquid movement as low
as 2 inch /sec across membrane.
The permeability of the membrane to oxygen varies greatly with temperature.
Therefore compensation is needed for this variation. The DO6 probe comes
with an in-built Temperature Compensation for the membrane variation.