Chat with us, powered by LiveChat

How is the DTG wavelength changing with temperature and strain?

Leider ist der Eintrag nur auf Amerikanisches Englisch verfügbar. Der Inhalt wird unten in einer verfügbaren Sprache angezeigt. Klicken Sie auf den Link, um die aktuelle Sprache zu ändern.

An FBG is sensitive to both strain (ε) and temperature (T) changes. In a simplified approximation, one can write:

Wwere λ is the FBG-wavelength; λ0 the wavelength at an arbitrary reference strain ε0 and a reference temperature TSε  the strain sensitivity or gage factor; ST  the temperature sensitivity; Δε = ε – ε the strain change with respect to the reference strain and ΔT = T – T0  the temperature shift with respect to the reference temperature.

The above formula holds for free FBGs and not for FBGs which are fixed to a structure, like for strain gages. In this case, formula (1) should be modified slightly due to the influence of the thermal expansion of the structure. If the structure has a linear expansion coefficient αt , then the thermal expansion of the structure is given by α. ΔT.  If this expansion exceeds the thermal expansion of the fiber glass, which is αf  ΔT , the structure exercises an extra strain on the fiber which is given by  αf) ΔT. Notice that the difference of the thermal expansion coefficients has to be taken because only the excess expansion will be transferred into strain. This strain gives an additional wavelength shift corresponding to Sε  αf) ΔT. The modified formula thus is given by:

It needs to be noticed that a more accurate approximation of the DTG® response is given by the following function:

where λ  is the DTG® wavelength; λ0 the nominal wavelength i.e. the wavelength at zero strain and at a fixed reference temperatureT0   S1 and Sthe temperature sensitivities and k  the strain sensitivity or gage factor. The strain ε is the mechanical strain that is experienced by the fiber. Due to the quadratic nature, the calibration parameters S1 and S2  are depending on the used reference temperature. For strain gauges supplied from FBGS,  the parameters S1 and S2  are determined for a reference temperature of 22.5°C.

This more complex formula is important to use when large temperature variations are expected and is standard implemented for strain gauges in the Illumisense software of FBGS.

Typical values for S1, S2 and k are:

S1 = 6.37E-06

S2 = 7.46E-09

k = 0.772

assuming T expressed in °C and ε expressed in strain.

The thermal expansion coefficient of te fiber αf  is typical around 0.5 μstrain/°C

Notice: Parameters S1, S2 and  αf do not take into account the influence of the coating.  

 

Für unseren Newsletter anmelden
Treten Sie in Kontakt mit uns
CAPTCHA image

* These fields are required.

Wie wir Ihre Daten verwenden

Wir verpflichten uns, Ihre Privatsphäre zu respektieren und Ihre persönlichen Daten zu schützen, und werden diese stets mit äußerster Sorgfalt behandeln. Wie wir mit Ihren Daten umgehen und wie wir sie verwenden, um Ihnen einen besseren Service zu bieten, finden Sie in unserer Datenschutzerklärung .

Mit dem Absenden dieses Formulars stimmen Sie der Verwendung Ihrer Daten in Übereinstimmung mit unserer Datenschutzerklärung zu.

Germany

FBGS Technologies GmbH
Winzerlaer Straße 2
D-07745 Jena

Belgium

FBGS International NV
Bell Telephonelaan 2H

B-2440 Geel

China

X2 Suzhou Electronic Technology
Room 103, No. 388
Xinping Str. SIP, Suzhou