Why measure dissolved oxygen online?

In biological processes like fermentation and cell culture dissolved oxygen is critical to support proper cell growth. In industrial processes, oxygen is often limited in applications where corrosion is of concern. Online oxygen measurement enables real-time control of dissolved oxygen at a predefined set point or enables the detection of a leak in the process that is resulting in oxygen infiltration.

Optical

The VisiFamily of optical dissolved oxygen sensors are quickly replacing polarographic installations due to a more robust measurement and minimal maintenance.

Polarographic

The OxyFamily of traditional polarographic sensors has an industry-leading two hour polarization time and modular design to simplify maintenance.

Single Use Optical DO

The VisiFerm sensing element can now come pre-installed and gamma irradiated in your favorite single use bag or bioreactor. Ask your single use provider today!

Polarographic vs. Optical

For over 60 years polarographic sensors have been used to measure dissolved oxygen through the electrochemical reduction of oxygen with a noble metal. More recently optical oxygen has gained prominence by eliminating polarization time, electrolyte, and complicated maintenance, by requiring only a single replacement part.


Optical Oxygen Sensors


The VisiFamily of sensors have a blue LED in the sensor shaft and an oxygen sensitive dye (luminophore) fixed to a glass window in the replaceable sensor cap. The blue light excites the luminophore and then a photodetector in the sensor shaft senses the red light that is returned from the luminophore. A microprocessor in the sensor correlates the emitted blue light and the measured red light to partial pressure of oxygen. This measurement can then be output as a simulated nA signal, 4 - 20 mA, or digital protocol.

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Polarographic "Clark Cell" Sensors

Classical Clark cell sensors have a platinum cathode and a silver anode that are separated from the sample by a gas permeable membrane. As oxygen diffuses across the membrane it is reduced resulting in a small nA current. The more oxygen the stronger the current. This current is then detected by a separate transmitter which amplifies the signal for process control.

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Specific Applications

Resources

Hamilton's knowledge base provides a range of explanatory articles, frequently asked questions, and document downloads.
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