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 from above?

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 is the λt ref coefficient for SWS-02 sensor found? 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.

Can some of the sensor templates be removed? Is there a password needed?

You can delete or rename a file called “SensorTemplates.xml” in the root directory, this will remove all stock templates.

How can a PC be connected to multiple interrogators if they are separated by a long distance (1km and more)?

The maximum distance for an ethernet cable connection is somewhere around 100m. Any longer and the signal gets distorted. If the unit is already positioned on the site location, another computer can be placed next to it. The distance for a USB cable connection is much lower, like 20-30m at maximum. Keeping a computer for each unit reduces the risk of communication loss and device damage. If one computer malfunctions, all other units connected to this PC will be disconnected. If every unit has a separate computer, the risk is mitigated to a minimum. Also, depending on the complexity of the calculation, speed of acquisition, etc. computer resources will be occupied by just one unit instead of multiple.

How can the test data be saved and what format do they save in?

To be able to save the data from the system, it is necessary to turn on the data logging feature inside the software with the appropriate settings. The data log is a *.csv formated file with a “;” (semicolon) as a separator.

How does the cable length affect the λt ref coefficient? Do we need to recalibrate the sensor during installation if we had done it before with the shorter fiber?

The readings are in direct correlation with the interrogator unit. Our units are spectrometer based and thus we don’t need to compensate for the fiber length as by the „tunable laser“ based interrogators. You can change the fiber optic cable without worrying about this.