In the field of geological hazard monitoring

deformation sensors based on parallel spiral transmission line can be used in tensile deformation distributed measurement

and the amount of stretching can be large

and there is a certain functional relationship between deformation magnitude and characteristic impedance. The structural characteristics and working mechanism of the parallel spiral transmission line are analyzed. Time domain reflectometry（ TDR） is used to measure characteristic impedance. The relationship between characteristic impedance and deformation size of the parallel spiral transmission line is obtained by electromagnetic field principle and finite element simulation. The experiment shows there is an exponential relationship between the characteristic impedance and the tensile deformation of parallel spiral transmission line. If the sampling precision of time domain reflectometer is high enough and the rising time of the step signal is short enough

this method can be used to realize the accurate distributed measurement of tensile deformation.