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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.

What is a Polarographic Dissolved Oxygen Sensor?

OxyFerm sensors


The OxyFerm polarographic dissolved oxygen sensor is specifically suited for hygienic applications in the pharmaceutical industry. The OxFerm CIP is designed to withstand frequent CIP cleaning procedures.

OxyGold G

OxyGold G polarographic DO sensors can measure down to parts-per-billion trace oxygen levels.


Oxysens polarographic dissolved oxygen sensors offer a simple, economical solution for measurements in fish farms, water treatment, and algae ponds.
Polarographic do sensor diagram

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


OxyFermOxyGold GOxysens
Measuring Range 10 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
Pressure Range 0 – 4 bar 0 – 12 bar 0 – 4 bar
Hygienic Aspects Autoclavable, CIP, SIP Autoclavable, CIP, SIP --
Electrolyte Oxylyte Oxylyte G Oxylyte
Surface Quality Ra < 0.4 µm (N5) Ra < 0.4 µm (N5) Ra < 0.8 µm (N6)
Current in Air 40 - 80 nA 180 - 500 nA 40 - 80 nA
Material Stainless Steel 1.4435 Stainless Steel 1.4435 Stainless Steel 1.4435
Polarization Voltage -670 mV -670 mV -670 mV


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