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Strain and Temperature MonitoringMeasuring by Fibre Bragg Gratings (FBG)
structures. Once applied,there is no need for any calibration or maintenanceof the sensor during its whole lifetime.
Alternatively, the sensorscan be fixed on already exis-ting structures.
Especially the immunity ofthe Bragg sensor againstelectric and magnetic fieldsqualifies the FBG measure-ment system for critical in-dustrial applications.
Thus the interrogation sys-tem is often used for moni-
toring and controlling of power generation and power transmission.
Further fields of application are automotive engineering, aerospaceindustry, high temperature monito-ring and SHM of composite materials.
REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
Embedded strain sensors in a concrete bridge
Vibration measurement during blasts in a open pit
System specification / Applications
We introduce a novel systemfor monitoring strain, vibrationand temperature based on op-tical fibre technology. This system has been developed forapplications like long termstructural health monitoring(SHM) for civil and industrialstructures.
It is used to measure strain, dis-placement and vibrations. Thissystem provides new perspec-tives for a detailed interrogati-on of various seismic or geophy-sical events and/or for measure-ments on buildings, bridges,power plants and other structu-res.
Compared with other techniques,the most important advantage of thesensors is its long term stability. If necessary, most of the sensor designscan be directly integrated into
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Strain and Temperature MonitoringMeasuring by Fibre Bragg Gratings (FBG)
System specification / Applications
For both the physiological compati-bility and the small physical dimensi-ons, the optical fibre sensor is favor-ably applicable in the field of biome-dical engineering, too. The active partof the Bragg grating sensor can be re-duced down to a size of only a fewmillimeters. Since its thermal capacityis very low, even fast fluctuations oftemperature are exactly measurableup to hundreds of Hz.
Reliable measurements are possibleeven under extreme conditions. Dueto its insensitivity to nuclear radia-tion, the fibre optic sensor is one ofthe very few options to measure directly in a concrete shielding of anuclear reactor.
The distance between interrogationunit and sensors can be a couple ofmiles without amplification of thesensor signal. Even a varying loss caused by connectors or microben-
ding effects of the optical cable doesnot impair resolution and accuracy,based on the fact that the strain ortemperature information is coded inthe frequency of light.
Monitoring of temperature and/orstrain of power transmission lines, data lines or trolley systems is neces-
sary for preventing damages causedby overheating or high wind/ice loads.
One important advantage is the pos-sibility of a direct embedding of theoptical FBG sensor into the cables andwires, without any decrease of theperformance.
REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
Plastic tube with
micro temperature
sensor inside
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Function of the FBG sensor
Principle of measurement
The Fibre Bragg Grating is a periodicchange of the refraction index insideof the optical fibre. It reflects onlylight with a certain wavelength whichis solely determined by the physicalstructure of the grating. This ware-length shifts by the strain and the heat which is induced locally in thesensor region.
REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
The light of a light source (LED) iscoupled into the optical fibre cablefrom one end of the fibre while theFBG sensor is situated near the otherend of fibre. The FBG reflects a part ofthe light with a determined frequen-cy which will shift due to inducedstress and/or temperature changes.The shift of the reflected light’s frequency is detected in the inter-rogation unit and then calculated into the corresponding strain/tempe-rature values. An internal or externalPC stores and displays the data.
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Software
The control software allows to storeand to display the measured data.The program calculates the strain ortemperature values from the fre-quency information provided by thesensor. It is adapted to each measure-ment system separately to ensure ahigh performance and stability. For amultichannel unit the software pro-vides an online monitoring and savingfor all channels simultaneously.
All basic functions are available, likeautomatic calibration, optical connec-tor test and time controlled opera-tion.
Additional smart features like an included event triggering, Excel™spreadsheet, as well as the possibilityto set up a periodic measurement ma-ke the system flexible and useful foryour individual measurement project.
Service
We recommend a two year mainten-ance interval and recalibration by ourengineers to ensure highest accuracyand absolute reliability. Beside this,the system is practically free of main-tenance.
For the adaptation of the system toyour individual needs, please contactour engineers. If requested, we arepleased to provide you our supportduring your whole measurement project.
REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
AWE-M2-4-PC: Monitoring unit with internal PC
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Configuration
Unit without internal PC AWE-M1-2-D with RS232
interface and analog outputs
Unit for field measurements with RS232 in a
Pelikan™ case (AWE-M1-1-D)
REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
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REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
High temperature multi-spotfibre optic measurement IndusTemp™
This fibre optic measurement system allows multi-spottemperature measurement in complicated industrial struc-tures, where the environmental conditions do not allowthe use of conventional techniques.
The system is specially adapted to hotspot monitoring inenergy plants, transformers, wires, reactors and relatedstructures. It provides an excellent long term stability andreliability for years.
fibre optic temperature sensor probe (metal coated FBG sensor) with variable cable length
signal processing (A/D converting, zeroing, referencing) with LCD display that shows the current temperature
Features Sensor Design
Sensor DesignSensor Response
Specifications
Measurement range -80 .. 600 °C Probe length < 3 m
Resolution <0.5 °C Display temperature in °C
Accuracy 1% v. Messbereich Power supply 230VDC 50Hz
Sample rate 1 .. 100 samples/sec Operating temperature 5 .. 45 °C
Measurement points of probe 1 .. 20 Interfaces RS232/USB
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REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
This long gauge strain sensor is desi-gned for being directly embedded into concrete structures or being applied onto the structure surface.
Prior to pouring the concrete, it isaligned to the reinforcement steel ofthe structure.
With a surface mounting anchor, theLG strain sensor can be installed easilyon concrete surface.
Long term health monitoring of civil structures
Crack detection in dams or bridges
Vibration monitoring of bridges and masts
Load watch of bridges or platforms
Long-Gauge (LG) Concrete Strain Sensor
Features Applications Package
Specifications
Measurement length [m] 1 .. 2
Measurement range [µm/m] -3,000 ... +8,500
Resolution [of range] 10-4
Accuracy [of range] 10-3
Operating temperature -20 ...80°
Cable length up to 1000 m
Optical parameters:
Wavelength bands [nm] 850 / 1300 / 1550
FWHM [nm] <0.3 or customized
Connector to be determined by customer
Application Example Field Test
The sensor is suit-
able for long term
monitoring
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REMBE®
FIBRE FORCE GmbH
Gallbergweg 2159929 Brilon/GermanyT + 49 (0) 29 61 - 74 05 - 83F + 49 (0) 29 61 - 5 07 [email protected]
This sensor was developed for a high resolution long term monitoringof strains induced by blasts, earth-quakes or other vibrations.
It is available for different resolu-tion classes (depending on the gainfactor). Therefore it is useful for the detection of vibrations with lowmagnitude.
High Resolution Strain Sensor
Applications Package
Measurement base [m] 0,5 .. 1
Measurement range [µm/m] 10.000 .. 400
Resolution [of range] 10-4
Accuracy [of range] 2 * 10-3
Cut-off frequency [Hz] 250
Optical parameters:
Wavelength bands [nm] 850 / 1300 / 1550
FWHM [nm] to be specified by customer
Reflectivity [%] >90
Connector FC/PC; FC/APC; SC/PC; SMA; E2000,
Specifications Standard
0,0 0,5 1,0-20
-10
0
10
20
23/03/2000 13:30:12:44
µstra
in
Time [sec]
1570 1572 1574 1576 1578
-40
-30
-20
-10
0
Loss
in dB
Wavelength in nm
Reflection Transmission
Spectral Characteristics (Example) Results of a Measurement
The sensor can
be mounted to
structures by
screws or a
special glue.
