Polarographic Dissolved Oxygen Sensors
Hamilton has been a leader in dissolved oxygen measurement for many years. The polarographic (amperometric) DO sensor product line includes the hygienic 12 mm sensor designs suited for applications in the bio-pharmaceutical, food, beverage and water treatment markets.
OxyFerm
OxyGold G
Oxysens
What is a Polarographic Dissolved Oxygen Sensor?
A polarographic sensor is commonly used to determine the dissolved oxygen concentration in a liquid. The dissolved oxygen will be reduced at the surface of a noble metal electrode, the working electrode, acting as a cathode:
O₂ + 2 H₂O + 4 e– → 4 OH–
A silver/silver chloride counter electrode, the anode, releases the required electrons:
4 Ag → 4 Ag+ + 4 e–
This electron flow from the anode to the cathode represents the measuring signal which is proportional to the partial pressure of oxygen in the measured solution.
The above decribed chemical reaction does not start automatically, but has to be imposed by an applied voltage which has to have at least the magnitude of the standard redox potential (+401 mV) of the reaction at the cathode, but with reversed polarity. This negative voltage, the polarisation voltage, must be absolute constant and has to be stabilized against a reference electrode.
Polarographic Dissolved Oxygen Sensor Articles
What makes Hamilton Polarographic sensors different?
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Simple to service
The plug-in cathode kit makes servicing the sensor quick and easy.
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Options
Hamilton offers specialized polarographic sensors suitable for trace oxygen measurement, high carbon dioxide environments, and sanitary applications.
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Approvals
Most Hamilton polarographic dissolved oxygen sensors have a variety of agency approvals making them suitable for multiple industries.
Specifications
| OxyFerm | OxyGold B | OxyGold G | Oxysens | |
|---|---|---|---|---|
| Measuring Range | 10 ppb - 40 ppm (DO) | 8 ppb - 40 ppm (DO) | 1 ppb - 40 ppm (DO) | 40 ppb - 40 ppm (DO) |
| Response Time t98% | < 60 s at 25 °C from air to nitrogen |
< 60 s at 25 °C from air to nitrogen |
< 60 s at 25 °C from air to nitrogen |
< 60 s at 25 °C from air to nitrogen |
| Pressure Range | 0 – 4 bar | 0 – 12 bar | 0 – 12 bar | 0 – 4 bar |
| Hygienic Aspects | Autoclavable, CIP, SIP | CIP | Autoclavable, CIP, SIP | -- |
| Electrolyte | Oxylyte | Oxylyte B | Oxylyte G | Oxylyte |
| Surface Quality | Ra < 0.4 µm (N5) | Ra < 0.4 µm (N5) | Ra < 0.4 µm (N5) | Ra < 0.8 µm (N6) |
| Current in Air | 40 - 80 nA | 180 - 500 nA | 180 - 500 nA | 40 - 80 nA |
| Material | Stainless Steel 1.4435 | Stainless Steel 1.4435 | Stainless Steel 1.4435 | Stainless Steel 1.4435 |
| Polarization Voltage | -670 mV | 0 mV | -670 mV | -670 mV |
| O-ring | EPDM | EPDM | EPDM | EPDM |
Resources
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Catalog - Process Analytics
Download the Process Analytics sensor catalog to learn about the complete offering of Hamilton process sensors and accessories. -
Brochure - BioPharma
Innovative solutions for process analytics in biotechnological and pharmaceutical industries. -
Brochure - Brewery
Learn about our control and analytical solutions that are essential to the brewing process.
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Does salinity impact my DO measurement?
Yes, salinity of a solution generally has an inverse relationship to the dissolved oxygen content within the solution. Arc sensors can have the salinity value of the liquid added in to correct the measurement by using ArcAir. -
Does temperature impact my oxygen measurement?
Yes, in a closed system, gas phase temperature is directly proportional to pressure and therefore measured oxygen content. In solution, temperature is inversely proportional to dissolved oxygen content. -
Does carbon dioxide sparging impact my DO measurement?
CO2 sparging will not impact the DO measurement using an optical DO sensor. CO2 can impact traditional polarographic DO sensors over time thus more frequent electrolyte replacement may be needed.
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Understanding Surface Finish
This article explores the topic of surface finish on wetted components for Hamilton sensors, housings, and other products.
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