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Galvanic DO probes do not
measure oxygen directly. They measure the partial pressure of
oxygen in the water, which is directly proportional to the percent
saturation of oxygen in the water. The concentration (mg/L or ppm)
can be calculated based upon the oxygen solubility, temperature, salinity
and total atmospheric pressure.
The DO probe consists of a
cathode, anode and an electrolyte separated from your process fluid by
an oxygen permeable membrane. The oxygen passing through the
membrane reacts to the cathode, giving up electrons, which produce an
electrical current proportional to the amount of oxygen present.
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Two types of membranes are
available, PTFE (Teflon) and HDPE. The standard membrane shipped
with the DO probe is PTFE due to its durability, resistance to
biological and chemical contamination and oxygen permeability over
temperature. PTFE is also recommended for indicators that have a direct
readout of ppm. The HDPE membrane is recommended for faster
responses to changes in oxygen levels or for indicators that are
calibrated for percent saturation readouts. For more information, visit http://www.sensorex.com
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