The low-

g

inertial switch is a kind of inertial device sensitive to the linear acceleration and achieves the switch closure when subjects to the applied acceleration.Due to its micro size

the switch is designed as a structure with the micro mass and low stiffness. To achieve a low stiffness beam in a micro plane

the planar spiral beam based on Archimedes' spiral is designed. The inertial switch is composed of a substrate

a frame structure

a cover plate and an inertial sensing element containing a sensor mass and a spiral beam.After analysing the inertial sensing element with an ANSYS and fabricating with an UV-LIGA

the laboratory centrifuge tests are performed on the low-

g

inertial switch to measure the on-state threshold. The result of the test is 21.27

g

which is the average of 21.22

21.39

and 21.20

g

. It is shown that the low-

g

mechanical inertial switch has a closed precision of 0.5

g

and good repeatability in multiple tests.