PSI - Issue 17

Kristýna Čápová et al. / Procedia Structural Integrity 17 (2019) 726 – 733 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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In Test 03, the response of the sensors to the ambient temperature change (in the range of -30 °C to 60 °C) was tested, while the interrogators were maintained in a constant temperature and humidity environment.

Fig. 3. Test 01 – record of the relative temperature change inside the interrogator.

The results of Test 03 test file showed negligible wavelength change within the range of 0,05 nm concerning the athermal 1512 sensor (FBG in the athermal casing). Linear and well-calibratable dependency was shown by strain sensor and temperature compensating sensor (Fig. 4 (a), fbgt). There is an evident hysteresis in the temperature dependence measured for the bare fibre in the Ormocer primary coating wound on a spool (Fig. 4 (b), Ormocer). The hysteresis appeared most probably due to the fibre shift in the winding on the spool.

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Fig. 4. Test 03 – dependence of the wavelength change of the sensor (a) fbgt_01_1000_1552 , (b) Ormocer on the ambient temperature.

The most important of the measured parameters of the internal sensors of the interrogator is the temperature of the spectrometer, which has a fundamental influence on the measured accuracy. This parameter was evaluated during the interrogators behaviour test at ambient temperature changes (Test 05) from the sensor labelled sys_spc_int_temp. During the test the ambient temperature of the interrogators was changed from 0 to 40 °C; the dependence of the connected external temperature and deformation sensors in the other climate chamber on the change of the internal temperature of the spectrometer was evaluated. In the tested range of 40 °C, the internal temperature of the spectrometer ranged from 26,5 to 27,5 °C. From the dependence measured by the athermal 1512 sensor (Fig. 5 (a), athermal 1512), it was found that changing the temperature of the spectrometer to 1 °C caused a change in wavelength indicated by the sensor to 0,007 nm. From the dependence measured by the optical fibre sensor with Ormocer primary protection (Fig. 5 (b), Ormocer), it was found that changing the temperature of the