The system consists of non-contact reflective fiber optic sensors

measurement and amplification circuits

field programmable gate array（FPGA） and displays.The laboratory test obtains the relationship between the voltage and the reflection surface distance.In practice

this function is used to calculate the length of the spring to be tested by measuring the voltage.The distance between the voltage and the reflection surface is calculated by the laboratory.The linearity is 1 %

the sensitivity is 1 V/mm

and the resolution is 0.01 mm.The actual resolution of the spring length is 0.01 mm.According to the national standard level 1

the length error of the spring is less than the standard spring ± 0.2 mm

which indicates that the system can fully meet the requirements of spring inspection

and has good linearity

high sensitivity and strong anti-interference ability.The accuracy of the actual test results of the optical fiber sensor is 100 %

and the precision is high

the cost is low

and the operation is simple.