Frequently Asked Questions (FAQ)
There is a λt ref coefficient in the calibration sheet. Does this refers to a factory wavelength or is it a calibrated reference temperature wavelength (i.e. at 0°C)
The λt ref corresponds to a value located inside our calibration sheets. This equals to the sensors wavelength at 22,5⁰C.
How is the temperature compensation property (mentioned in datasheet) achieved?
The sensor includes a second FBG that measures only the variation in temperature and is used for compensating the strain gauge for temperature effects. The FBG can measure absolute temperature although we don’t recommend it as a replacement for a dedicated temperature sensor. The sensor can be also produced without the second FBG (temperature). In that case, you can use the readings from adjacent sensors for compensation. Please note, we have inside our portfolio also a dielectric strain gauge (DSS-01) with the same dimensions as the SWA-01.
The product calibration sheet includes two different wavelengths. Is this a range of wavelengths or two different peaks for two FBG? Is this related to integrated temperature compensation property?
The lower wavelength is standardly corresponding to the temperature FBG used for the temperature compensation and the second FBG is for strain measurement. Since the sensor does not feature any pre-strain from the factory, during the installation the strain FBG will shift away from the temperature FBG until it the sensor reaches the desired value of pre-strain.
How to find the λt ref coefficient for SWS-02 sensor? And how does cable length affect the λt ref coefficient in this case?
The λt ref. coefficient is listed inside the calibration sheet together with the equation for transforming the wavelength change to strain or temperature change.