Fig. 1. Diagram of extrinsic fiber F-P sensor structure

Fig. 2. (a) Displacement distribution of diaphragm under unit stress; (b) the first order natural frequency amplitude-frequency characteristic curve

Fig. 3. (a) Photograph of transformer oil dynamic viscosity detection device; (b) transformer oil dynamic viscosity varies with temperature

Fig. 4. Amplitude-frequency characteristic simulation charts of (a) F-P1 and (b) F-P2 sensors in air and transformer oil at 20 ℃

Fig. 5. Amplitude-frequency characteristic simulation charts of (a) F-P1 and (b) F-P2 sensors in transformer oil at 20 ℃, 50 ℃, and 80 ℃

Fig. 6. Extrinsic fiber F-P sensor ultrasonic measurement system

Fig. 7. F-P sensor sample

Fig. 8. Amplitude-frequency characteristics of (a) F-P1 and (b) F-P2 sensors in transformer oil at 20 ℃, 50 ℃, and 80 ℃

Fig. 9. Natural frequency of the F-P sensors varies with the transformer oil temperature curve

Fig. 10. Packaged F-P sensor diagram. (a) Structure diagram; (b) photograph of real product

Fig. 11. Amplitude-frequency characteristics of (a) F-P1 and (b) F-P2 sensors in air at 20℃, 50 ℃, and 80 ℃

Fig. 12. Amplitude-frequency characteristic charts of F-P sensors with packaged and unpackaged structures in transformer oil at 20 ℃. (a) F-P1; (b) F-P2