Sensors

Sensor module quickly measures changes in oxygen concentration

17th June 2015
Siobhan O'Gorman

An oxygen sensor module that can be used in demanding applications where response times are important when measuring changes in oxygen concentration has been introduced by Pewatron.The key element of the FCX-MC25-CH is the oxygen sensor developed by Fujikura. It is an amperometric solid-state sensor with high output accuracy, short response time to gas concentration changes and resistance to pressure change, humidity and other gases.

The non-amplified logarithmic signal from the oxygen sensor is in the microamp range. The sensor module is a signal conditioning unit that amplifies the sensor’s current output and has an analogous, low-noise, linearised current output of 4-20mA. Due to its low total power consumption of less than 3W, the FCX-MC25-CH oxygen sensor module is suitable for mobile applications.

Typical applications requiring a fast response time by the sensor include those where only small sample extracts are available for analysis or where a large number of samples are to be tested/analysed. For both applications, knowledge about the response time is important to be able to make correct assessments of the process and product quality.

Selective laser melting is a good example of an application where the response time of the oxygen sensor is important when measuring changes in oxygen concentration. When using metal powder to build a 3D model via laser sintering, minor alterations in oxygen concentration can cause major structural changes to the model due to unwanted selective oxidation of the metal layers. It is important to monitor the oxygen changes in the chamber and to couple these changes to counteractions, e.g. by increasing the vacuum pump speed. It is important for the steel metal system, and highly important for metal systems featuring aluminium, titanium or nickel, to be able to react to sudden changes in oxygen concentration during the process.

The oxygen sensor is configured in a flow configuration with connectors for hosing. The sensor is encapsulated in a pressure-proof aluminium flow housing, enabling oxygen concentrations to be analysed from small sample extracts. The output oxygen concentration is highly linear, with a degree of accuracy greater than +/-0.5% vol. O2. It also has a response time of less than five seconds for gas concentration changes. Concentration ranges are from 0 to 25% vol. O2.

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