Ocean Optics OOISensors - Manual (Page 83)

6: Hardware Data Sheets and Instructions
Sampling Chambers
The oxygen probe should be installed in a suitable sampling compartment. If you are not using an
overcoat on the probe, it is critical that ambient light be excluded from the field of view of the probe tip.
For gases, a flow chamber with connections to N
2
, dry air, and/or O
2
is suggested. For fluids, these gases
can be used with glass frits (airstones) and a stirrer to bring the liquid into equilibrium with the calibration
gas. As an option, sodium hydrosulfite can be used to strip O
2
from aqueous solutions. It is critical that
standards with known oxygen concentration levels are available for use.
Ocean Optics has both clear and black/opaque sampling chambers available for sale in various sizes.
Consult an Applications Scientist for more information.
Response Time
The response time of a oxygen probe is limited by the speed of diffusion of oxygen into the sensor. Our
standard thin films are very fast (<1 second) in gases and liquids. In viscous samples, the diffusion
through the sample will determine the response rate. The probe will respond quickly in samples such as
water, and more slowly in viscous samples such as oils, emulsions, and creams. Unlike an electrode, the
optical sensor will not consume oxygen. This means that stirring the sample will increase the response
rate, but will not affect the final equilibrium reading. Also, optional probe overcoats, applied to exclude
ambient light and improve chemical resistance, will slow response time from 20 seconds to as long as 90
seconds, depending on the overcoat.
Environmental Conditions
Environmental changes, such as changes in pH, salinity, and ionic strength, do not affect oxygen probes.
Chemical Compatibility
Oxygen probes are not affected by pH change or salinity. They can be used safely with 50% methanol,
acids, sodium sulfite, NF
3
, hexane, CH
4
, acetone vapor, moisture, CO
2
and CO. We recommended not
using the probes with strong bases (pH>10), styrene, ethanol, liquid acetone, acetonitrile, and HF and
BTEX solvents.
For a complete list of disruptive and benign chemicals for use with oxygen probes, see Chemical Effects
on Oxygen Probes .
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