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OX-NP tip_700x400
O2 UniAmp_700x400
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Designed for research applications within:
Environmental Sciences
Biomedical Sciences

O2 microsensor

High performance O2 microsensor

With tip sizes of only 2-3 µm, you can measure oxygen at high spatial resolution without damaging your sample. You can choose a response time of less than 0.3 sec and attain fast and accurate oxygen measurements thanks to the insignificant oxygen consumption. Read more...

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Technical Data
Ordering Information & Sizes
Manuals & Videos
O2 Microsensor

Oxygen microsensor principle

The oxygen microsensors are all Clark-type sensors measuring oxygen partial pressures. The working principle of the oxygen microsensor is based on diffusion of oxygen through a silicone membrane to an oxygen reducing cathode. The reducing cathode is polarized against an internal Ag/AgCl anode.

The oxygen microsensor has a guard cathode that removes oxygen in the electrolyte, thus minimizing zero-current and pre-polarization time. The resulting sensor signal is in the pA range and is measured by a high quality picoammeter, such as the UniAmp Multi Channel.

OX-500 sensor tip_1400x800
Cables & Connectors
Stirring Sensitivity & Response Time
Feature Standard Options Extra price for option selection
Total length 150-200 mm 70-350 mm 10-50%
Diameter 20 mm from tip <2 mm <1 mm 10%
Diameter 50 mm from tip 8 mm <2 mm 20%
Glass shaft diameter 8 mm 6-20 mm 20%
Plastic shaft protection diameter* 11 mm Can be omitted

*When mounted with in situ mini connectors, the shaft has no protection mounted, but fits directly into the in situ sensor mounts with pressure compensation. In situ sensors have a standard length of 130-160 mm.

Cables & Connectors
Item Standard Options Extra price for option selection
Cable Habia
Cable length 1.5-2 m 0-20 m Yes, depends on length
Connector LEMO BNC adapter Yes, order separately
In situ gold pin connector* No Yes

*When mounted with in situ mini connectors, the shaft has no protection mounted, but fits directly into the in situ sensor mounts with pressure compensation. In situ sensors have a standard length of 130-160 mm.

Attribute Standard Options Extra price for option selection
Guaranteed lifetime 6 months (modifications not included)
Guaranteed lifetime OX-Eddy 2 months
Expected lifetime >1 year*
Temperature range -10-60°C
Temperature range tip -10-60°C (not needle versions) -10-90°C (organic electrolyte - not needle versions) 20%
Temperature coefficient 2-3% per °C
Range About 0-1 atm pO2 Optimization of high range
Detection limit 0.3 µM 0.050 µM 10%
Internal guard Yes Can be omitted
Waterproof Yes
Pressure tolerant sensing tip Yes
Tip colour Glass Black painted Contact Unisense
Electrolyte with fluorescein (fluorescent) No Yes 10%
Spatial resolution Equals outside tip diameter
Response Linear
Sensor oxygen consumption 2.5-25.0 x 10-10 mg O2/min equals approx. 4*10-4 - 5*10-3 nmol/hour

*Shorter lifetime may be experienced for oxygen sensors with tip diameter of 10µm (OX10) including the OX-Eddy microsensor.

Stirring Sensitivity & Response Time
Item Stirring sensitivity Response time (90%) Extra Price
OX-10 standard <2% 1-3 s -
OX-10 fast <5% <0.3 s 15%
OX-25 standard <2% <4 s
OX-25 fast <5% <0.5 s 15%
OX-50 standard <2% <5 s
OX-50 fast <5% <1 s 15%
OX-100 standard 1.5% <8 s -
OX-100 fast 5% <2 s 15%
OX-200 standard <1.5% <8 s -
OX-500 and OX-MR standard 1.5% <15 s
OX-500 and OX-MR fast <5% <3 s 15%
OX-Eddy Standard 150-200 µm <1% <0.4 s
OX-Eddy 40-60 µm 1% <0.3 s
OX-Eddy 90-100 µm 1% <0.4 s
OX-N exposed tip <2% <10 s
Ordering information & Sizes
Ordering information & Sizes
Oxygen Sensor Size and description Options Extra price for option selection
OX-10* 8-12 µm - glass sensor 3-5 µm 20%
OX-25 20-30 µm - glass sensor
OX-50 40-60 µm - glass sensor
OX-100 90-110 µm - glass sensor 100-400 µm 20%
OX-100 Ultrafast 90-110 µm - glass sensor Faster than 0.4 s 15%
OX-200 175-225 µm - glass sensor
OX-500 400-600 µm - glass sensor 600-800 µm 20%
OX-Eddy 150-200 µm - for Eddy Correlation System OX-Eddy (40-60 or 90-110 µm) 20%
OX-MR 400-600 µm - in guide
OX-N 1.1 x 40 mm - needle sensor
OX-NP 1.6 x 40 mm - needle sensor for piercing
OX-ST-1/4 1/4'' steel tube
OX-SL-1/4 FT-cell 1/4'' Swagelok Tee
OX-SL-1/8 FT-cell 1/8'' Swagelok Tee
OX-PEEK-1/8 FT-cell 1/8'' PEEK Tee
OX-PEEK-1/16 FT-cell 1/16'' PEEK Tee
OX-FT-GLASS-6 Glass FT-cell 6 mm outer diameter
OX-FT-GLASS-8 Glass FT-cell 8 mm outer diameter

*In the standard design the oxygen sensor is optimized for stirring sensitivity and response time. It can however be useful to focus on optimizing one of the parameters for special applications. Unisense offers to optimize the sensor concerning one or both of the above mentioned parameters. Optimization of these parameters makes the production more difficult, therefore the extra price.

Video Guides

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Quick Guide O2 Microsensors

A walk-though of how oxygen microsensors are made, how they work, specifications, and customizations.

O2 Calkit contents
O2 Calibration Kit Video

Application Scientist Tage Dalsgaard shows you how to perform a 2-point calibration with a zero oxygen solution and water at atmospheric saturation

Related publications

An oxygen microsensor with a guard cathode
Revsbech, Niels Peter (1989), Limnology and Oceanography, vol. 34, 474-478
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Odor-Evoked Oxygen Consumption by Action Potential and Synaptic Transmission in the Olfactory Bulb
Lecoq, Je et all (2009), Journal of Neuroscience, vol. 29, 1424-1433
Read more
Long-term viability and function of transplanted islets macroencapsulated at high density are achieved by⁠…
Evron, Yoav et all (2018), Scientific Reports, vol. 8, 6508
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Nitritation performance in membrane-aerated biofilm reactors differs from conventional biofilm systems
Lackner, Susanne et all (2010), Water Research, vol. 44, 6073-6084
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