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SNAP-ACTION MECHANISM AND SHOCK RESISTANCE

When a switch is intended for harsh environments, its level of resistance to shocks and vibrations must be considered.Shock resistance measures the electrical contact reliability and more particularly the capacity to maintain the electrical function in case of shock or strong vibrations. The IEC 512-4c/4d standard defines the tests measuring the resistance level by evaluating the capacity of the switch to withstand successive strong accelerations and decelerations.

PRINCIPLES

Two points must be evaluated to choose the right switch:Contact pressure: the higher it is, the better resistance level it will have.Switch weight: lightweight mechanisms have a better shock resistance because they are less submitted to inertia.The « snap-action » mechanism combines these two features.It is a quick-break mechanism without intermediate state. Switching is obtained by the deformation of a spring or moving contact when the switch is operated.Choosing a « snap-action » mechanism allows combining a standard operating force and a high contact pressure. For this reason, in case of shocks or strong vibrations, there is no risk of contact without actuator operation. Moreover, to be easily deformable, the moving contact must be thin and light and these two features make it intrinsically resistant to shocks (low inertia).

TESTS

Two tests permit to verify the conformity to the IEC 512-4c/4d standard specifications.Vibration test on a vibrating table allowing precise configuration and vibrations in 2 or 3 directions.Shock test with a device mounted on 2 columns and simulating the fall of the tested product. The generic value of deceleration to which the product is submitted is equivalent to 50g.

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