Oxygen Sensor Calibration

NeoFox oxygen sensing systems from Ocean Insight are the only oxygen sensors of their type that can be calibrated to a specific experiment environment. While other sensing systems are sold with a single, factory-defined calibration, or require users to take their own on-site references, NeoFox is available with custom calibration regimes that cover the precise oxygen pressure and temperature ranges you expect to encounter during your measurements.

Optical Oxygen Sensors Calibration: Background

Sensor calibration in gas or liquid phase is necessary to ensure that your system reads oxygen levels accurately over the oxygen pressure and temperature range of your measurements. You can calibrate the system in your sample environment or have Ocean Insight calibrate the system prior to shipment.

Because the raw sensor signal is affected by the oxygen partial pressure, the temperature and the physical properties of the sample, it is important for measurements in non-isothermal environments to have temperature compensation worked into the calibration.

In NeoFox sensor setups, temperature affects both fluorescence intensity and excited state lifetime, resulting in a change in the calibration slope. To avoid false partial pressure readings, the sample must be held at constant temperature (±3 °C), or corrected for temperature.

Optical Oxygen Sensors Calibration: In-house Services

Ocean Insight oxygen sensors produce a fluorescence lifetime, or tau value, as a function of partial pres­sure of oxygen and temperature. To account for these temperature effects, we calibrate our sensors across a range of temperatures. By generating oxygen re­sponse curves at various temperature levels, a set of polynomial relationships are determined to provide precise oxygen readings despite changes in environ­mental temperature.

To calibrate oxygen sensors, we use ro­bust, fully automated environmental chambers that support up to 8 NeoFox channels. A custom gas dilution system feeds four ultra-high purity (UHP-grade) gas standards to a series of mass flow control­lers that output oxygen concentrations with 0.05% precision. The gas flows through a manifold with fit­tings designed to integrate all our oxygen sensor prod­ucts. The manifold sits in a Thermotron^® environmen­tal chamber that quickly moves the sensors across the calibration temperatures.

Optical Oxygen Sensors: In-house Calibration Options

Ocean Insight oxygen calibration services are offered in three versions:

Standard. The O2-CAL-STANDARD option runs the sensors through the most common ambient-range conditions. This includes a 0-25% oxygen range at 1 atm and 15-35 °C temperature range, using 11 oxygen concentrations and 9 temperature points across this distribution:

Custom. The O2-CAL-CUSTOM option allows users to select the exact oxygen and temperature ranges for their sensor, and allows grouping of points for higher accuracy in select conditions. These ranges are available for the various oxygen sensor chemistries: