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Industrial pressure switches may have a calibrated scale and pointer to show the set point of the switch. A pressure switch will have a hysteresis, that is, a differential range around its setpoint, known as the switch's deadband, inside which small changes of pressure do not influence the state of the contacts. Some types allow adjustment of ...
Contacts may be operated by humans in push-buttons and switches, by mechanical pressure in sensors or machine cams, and electromechanically in relays. The surfaces where contacts touch are usually composed of metals such as silver or gold alloys [3] [4] that have high electrical conductivity, wear resistance, oxidation resistance and other ...
The actuation force is the force required to collapse the membrane of a rubber switch, and the contact force is the force required to maintain rubber-switch contact closure with a printed circuit board. Mathematically, this can be represented by: Snap ratio = (F1 - F2) / F1. where F1 is the actuation force, and F2 is the contact force.
Contact resistance values are typically small (in the microohm to milliohm range). Contact resistance can cause significant voltage drops and heating in circuits with high current. Because contact resistance adds to the intrinsic resistance of the conductors, it can cause significant measurement errors when exact resistance values are needed.
Providing a sufficient amount of wetting current is a crucial step in designing circuits that use switches with low contact pressure. Failing to do this might result in switches remaining electrically "open" when pressed, due to contact oxidation. [4] [5]
IEEE 315 Contacts, Switches, Contactors, and Relays Symbols (6).svg (in English) (1993) 315-1975 - IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters) , IEEE, p. 64 DOI : 10.1109/IEEESTD.1993.93397 .