Aos Products
 

Miniature fibre pressure sensor

Designed as part of an on-going investigative programme  these prototype fibre-scale pressure and/or temperature sensors are ideal for integration into sensing environments that have either strict physical constraints, required high E.M.I. immunity, minimal structural disruption  or have  limitations placed upon the materials used.  The basic sensing element consists of a hollow micro-balloon attached to the end of a singlemode optical fibre, Fig 1. The balloon is sieved, selected, washed, aligned and attached to a SMF

Micro-balloon attached to SMF fibre

using a proprietary alignment method that incorporates continual on-line spectral monitoring.

The structure is further processed to greatly enhance the spectral characteristics of the sensor before encapsulation within the material of interest or as a stand-alone optical sensor.  Temperature sensors can be manufacturing using this sensing element with the addition of pressure screening.

When designed as a temperature sensor these devices have extremely small thermal mass and can response to small transient changes in temperature otherwise unseen by standard thermocouple, thermistor or NTC probes. Tests results detailed in the graph below show the temperature response of a pressure isolated sensor embedded in a silicone capsule.  The thermal response id due to material heat and cooling when subjected to compression and expansion loads respectively.

The micro-balloon sensor produces a modified Fabry-Perot response characteristic that can be tuned by:

  • Changing the balloon size

  • Modifying the adhesive type

  • Varying the encapsulant

  • Changes in balloon coating technology

Since each of these parameters has an effect upon the response of the sensor as a whole it is difficult to provide a simple sensor specification. Suffice to say a number of different environmental needs can be met with sensors covering a range of both temperature and pressure measurement capabilities.

 

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         AOS Technology Ltd, 14 Pate Road, Melton Mowbray, Leicestershire, LE13 0RG, UK    T: 01664 567711