Sensor Deployment

As a result of many years of experience in a wide range of applications, Epsilon Optics have accumulated considerable expertise in the design and manufacture of sensors and their deployment methods. This enables the supply of sensors that not only perform accurately and reliably in the operating environment, but are also easy to install in the case of existing structures, or easily integrated into the manufacturing process in the case of new structures. By pre-connectorising the sensor arrays and interconnecting cable, the optical elements of an installation becomes almost "plug & play".

Installation Examples

Super Yacht Mast Installation Aviation Installation
Combined Strain & Temperature Sensor Patches being installed in a Super Yacht Mast
Combined Strain & Temperature Sensor Patch installed on aircraft landing gear.

This expertise and know-how is equally applicable to sensors designed to work with TDM or WDM type FBG interrogators. Epsilon Optics can supply and support either type in order to suit the requirements of the particular application. We have a number of international patents which cover sensor embedment, temperature sensors and discrete fibre optic sensing devices.

Key Features

Surface Bonded Sensor Patches

  • Ease of installation, reducing time and cost, rugged and easily installed by non-skilled labour.
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  • Up to 100 of sensors in an array.

 

Embedded Sensors

  • No impact on the component’s external surface, measurement of strains within the component and are very well protected.

 

Discrete Sensing Devices

  • Easy to install with high degree of robustness and pre-connectorised.

 

TDM & WDM Interrogators

  • Sensor arrays can be manufactured to work with both interrogator technologies.
Surface Bonded Sensor Patch

The optical fibre is mounted within a patch normally manufactured from low modulus glass fibre. The patch is shaped to suit the component to which it is to be attached and the FBGs are located in their required positions.

Standard strain sensor patch Patented temperature sensor patch
Standard Strain Sensor Patch
Flexible, rugged and easy to handle.
Patented Temperature Sensor Patch.
Multi Sensor Patch Custom strain sensor patch
Multi Sensor Patch
Single patch with 4 FBGs comprising a strain rosette with 0, +45, -45 degree sensors and a temperature compensation sensor.
Custom Strain Sensor Patch
Manufactured to conform accurately to the shape of the structure.

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Key Features

Surface Bonded Sensor Patch:

  • Ease of installation which significantly reduces both time and cost.
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  • The patch’s low stiffness and relatively large bond area greatly reduces the shear strain on the bond when compared with conventional resistive strain gauges, significantly improving the life of the sensor.
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  • The ingress and egress of the optical fibre can be engineered into the patch adding to the robustness of the installation.
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  • Sensor patches can be used on both metallic and composite structures.
  Sensor Patch Cable Ruggedisation

Epsilon Optics offers a wide variety of cable ruggedisation options for connection to, and interconnection between sensor patches or devices. The degree of protection is engineered to suit a particular application or environment. Pre-connectorisation means that customised patches can be manufactured to suite the structure being monitored and connected essentially as a "plug & Play" package.

Key Features

Sensor Patch Ruggedisation Options:

  • Ruggedisation to suit application environment.
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  • Pre-connectorised and robust allowing installation by non-skilled workers.
Kevlar reinforced pigtail Aviation grade kevlar reinforced pigtail PVC Coated micro-stainless steel flexible conduit PU TUbe with Kevlar reinforced Pigtail
Kevlar reinforced pigtail.
Aviation grade kevlar reinforced pigtail.
PVC Coated micro-stainless steel flexible conduit.
PU Tube with Kevlar reinforced Pigtail.
Silicon Coated Steel Flexible Conduit Stainless Steel Braid Hydraulic Hose Stainless steel flexible conduit with kevlar reinforced pigtail Stainless steel flexible conduit with loose Tube
Silicon Coated Steel Flexible Conduit
Stainless Steel Braid Hydraulic Hose.
Stainless steel flexible conduit with kevlar reinforced pigtail.
Stainless steel flexible conduit with loose Tube.
Continuous Sensor Arrays

Epsilon Optics have developed the the manufacturing process that allows dozens of sensors to be built as a single chain of ruggedised sensors.

Standard strain sensor patch
Sensor Array Chain Containing 50+ Sensor Patches.
Key Features

Continuous Sensor Arrays:

  • Custom arrays optimised to the structure being measured.
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  • Reduces the amount of cabling and simplifies the installation and saves on time and cost.
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  • Up to 100 sensors possible in a single array.
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  • Temperature compenstion sensors built as part of the array.
Manufacturing the sensors in a chain array simplfies installation minimising the amount of cabling required and minimises installation time. The chain arrays can be stored on a reel that can be simply unrolled as each subsequent sensor is being installed.The arrays often consist of a chain of strain sensors interupted by the occasional temperature compensation sensor. The distance between each sensor and the interconnecting cable and optical connectors to the interrogator can all be specified.
Embedded Sensors:

The optical fibre with its FBGs can be embedded in composite structures with minimal intrusion and no detrimental effect on the mechanical properties of the structure (see note). Although the diameter of an optical fibre is much larger than that of a glass or carbon fibre used in a composite structure, their mechanical properties are very similar. In this way a properly embedded sensor can be considered an integral part of the structure and will last the lifetime of the structure, even over many millions of fatigue cycles.

Embedded Sensor Installing
Picture taken by electron microscope showing the cross section
of an optical fibre embedded in e-glass/epoxy composite
Installation of FBG sensors in pre-preg composite

 

Sensor Veil Array

In order to avoid both the technical problems and the need for a fibre optics specialist to install the sensors, Epsilon Optics has developed the Sensor Veil Array which comprises a dry (un-impregnated) veil cloth in e-glass or carbon fibre, with a fibre-optic sensor array fixed to it. The optical fibre layout and sensors are all precisely located and the optical fibres brought out via a suitably ruggedised cable which can be pre-connectorised.

Key Features

Embedded Sensors:

  • No impact on the component’s external surface. This is important where the component provides an aerodynamic surface such as a helicopter rotor blade.
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  • It is possible to measure strains within the component.
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  • The embedded sensor is very well protected and is available for the life of the component.

Sensors Veil:

  • Pre-configured "made to measure" infusable patches that simplify the embedment process.
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  • Dry un-impregnated patches make them compatible with majority of resin systems and prodcution processes.
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  • Sufficiently rugged to enable installation by customers production personnel.
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  • Significantly reduces both time and cost of sensor embedment.
Sensor Veil Cloth

 

Whilst not being as robust as a surface bonded sensor patch, the Sensor Veil is resilient enough to be installed with confidence by a suitably trained laminator. In this way the entire array which may include many sensors can be accurately positioned in the laminate stack

The Sensor Veil concept is suitable for pre-preg, wet lay-up, vacuum infusion, resin transfer moulding and similar processes. Where closed moulds are being used there will need to be provision made for the cable exit. Where a vacuum bag is used the Sensor Veil can be combined with one of our surface mounted connector housings located on the final laminate under the vacuum bag.

Sensor Veil Array (dry un-impregnated),
Surface Mount Connectors:

The ingress/egress point of the optical fibre from the composite can be particularly vulnerable to damage both during manufacture and subsequent use if not properly engineered. To address this problem Epsilon Optics has developed a number of connector enclosures suitable for surface mounting and being fully compatible with most production processes (vacuum bagging, autoclave, vacuum infusion etc.). The enclosures are supplied complete with a blanking cap ensuring the cleanliness of the optical connector throughout the manufacturing process.

Embedded connectors Diamond Mini Avim Embedded connectors FC-APC Embedded connectors Diamond Avim
Diamond miniAVIM FC-APC Diamond AVIM

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Key Features

Surface Mount Connectors:

  • Available to suit a range of aerospace and communications type connectors.
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  • Provides a ruggedised fibre-optic. connection from a composite structure
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  • Ease of termination ideally suited to manufacturing environments.
Discrete Sensing Devices:

The optical fibre and its FBGs are mounted within a composite carrier which is shaped such that it can be locked or clamped to the structure. The carrier follows the changes in shape of the parent structure and thus measures the loads applied to it. A number of variations have been developed including sensors for detecting cracks and for measuring displacements of civil engineering structures. They have also been used on complex metallic structures such as aircraft landing gear.

Pultruded Rod Embedded Sensor Long guage Sensor
Micro-Tenex © pultruded rod sensor In-axle sensor for aircraft landing gear Long Guage Length Displacement Sensor

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Key Features

Discrete Sensing Devices:

  • Ease of installation.
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  • High degree of robustness.
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  • Pre-connectorisation available
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Epsilon Optics has worked with a number of manufacturers of composite components to successfully embed optical sensors and has developed techniques for all common composite manufacturing processes including:

  •  Hand lay-up         Vacuum infusion        Resin transfer moulding        Filament winding        Pultrusion        Pre-preg        Autoclave processing

Note: A number of trials have been conducted by several of our Aerospace customers, comparing the strength and resistance to fatigue of components, with and without Epsilon Optics embedded sensors. Provided the sensors are embedded in accordance with Epsilon Optics best practice, no measureable knock-down in performance was detected.

Design and implementation of complete fibre optic sensing solutions