Name: ELITON MATHIAS MORAIS
Publication date: 07/03/2022
Advisor:
Name |
Role |
|---|---|
| ARNALDO GOMES LEAL JÚNIOR | Advisor * |
| MARIA JOSE PONTES | Co-advisor * |
Examining board:
| Name |
Role |
|---|---|
| ANSELMO FRIZERA NETO | Internal Examiner * |
| ARNALDO GOMES LEAL JÚNIOR | Advisor * |
| MARIA JOSE PONTES | Co advisor * |
Summary: This paper presents a fiber optic liquid level sensor system based on a pair of fiber gratings (FBGs) embedded in a circular silicone rubber (PDMSpolydimethylsiloxane) diaphragm and a nitric rubber diaphragm. The measurement principles of these sensors are
presented. The silicone rubber diaphragm sensor is about 2.2mm thick and 45mm in diameter. To analyze the linearity and sensitivity of the sensor, the diaphragm was subjected to compression tests as well as liquid level loading and unloading. Force and liquid level rise tests showed that inserting two FBGs (0.99453 for force and 0.99163 for liquid level) into the diaphragm resulted in a system with greater linearity than with individual FBGs. This occurred WHERE FBG1 presented 0.97684 for force and 0.98848 for liquid level and FBG2 presented 0.89461 for force and 0.93408 for liquid level. However, the compression and water level reduction tests showed that the system (R2 = 0.97142) showed higher linearity with FBG2
(0.94123) and lower linearity with FBG1 (0.98271). Temperature characterization was also performed and we found that the sensitivity to temperature variation for FBG1 was 11.73 pm/°C and for FGB2 it was 10.29 pm/°C. Temperature sensitivity was improved for both FBGs when compared to uncoated FBGs with typical values of 9.75 pm/°C. Therefore, the proposed FBGbased sensor system is capable of simultaneous force and temperature measurement in a compact diaphragm-embedded system. The nitrile diaphragm sensor is constructed of 3 layers of rubber with two FBGs inserted into the diaphragm. 4 configurations were constructed, WHERE the thickness of the central layer was varied. To analyze the linearity and sensitivity of the sensor, the diaphragm was subjected to bending tests, WHERE configuration 1 presents greater linearity with two FBGs (0.93326) than configuration 1. FBG1 (0.90998) and FBG2 (0.77451) alone. In configuration 2, the system showed greater linearity with two FBGs (0.85881) than FBG1 (0.85549) and FBG2 (0.85618) alone. For
configuration 3, the system showed greater linearity with two FBGs (0.93103) than FBG2 (0.92189) alone, and lower than that of FBG1 (0.93332). Finally, configuration 4 presented a system with greater linearity with two FBGs, since the R2 of the response of both FBGs
(0.95207) is greater than that of FBG1 (0.94218) and FBG2 (0.81784) alone. Temperature characterization for all 4 settings resulted in a value lower than the sensitivity normally found
in uncoated FBGs (9.75 pm/°C).
