How Does Wetting Current Work?Ī wetting current is the minimum amount of current required to send through a mechanical switch to break through oxidation film that gets deposited on the switch contacts. As an example, a two pole switch will have two sets of contacts (that are identical) which can be controlled by the same knob. The total number of poles refers to the total quantity of circuits that are controlled by a switch.
For example, a double-throw switch consists for a contact capable of being connected to one of two other contacts. The number of throws refers to the total number of positions that can be adopted by the switch. If a switch includes both types of contact, it is called a changeover switch.Īnother way that switch contact variations are described is by the number of throws or poles that are included in the switch. Other terms used to label these positions include “make” for contact closure and “break” for the opening of contacts.įor a switch that is designed for contacts to remain in a single state unless actuated, the contacts will be labeled as either normally closed or open until their state is changed by the operation of the switch. When there is separation preventing current flow between the contacts, the switch is said to be open. When current can flow from one contact to another, a switch is said to be closed. How is a Switch Classified?įor use in electronics, switches are normally classified to how the contacts are arranged. In some switch designs, engineers may use a minimum wetting current in order to help prevent insulating oxides from forming. Other qualities considered for contact materials in switches include cost, low toxicity, hardness, mechanical strength, and electrical conductivity. This is due to the fact of most metals forming an insulating oxide that prevents a switch from operating properly. Engineers will normally choose the contact material for the circuit for its ability to resist corrosion. These contacts are commonly made up of metal and they are normally required to touch to complete the circuit and to separate to open the circuit. The most basic switch has two contacts or conductive pieces that are connected to an external circuit. The two types of momentary switch commonly used throughout industry are push-to-break and push-to-make types. They can be found in all manner of electronic devices and usually take the form of a button to help initiate the state change in a device. This type of switch can actually represent one of two types with the alternative being the traditional on or off switch. A common question asked by new student of electronics is what is a momentary switch? The short answer is that a momentary switch is a unit capable of turning any electronic device to either an on or off state when an end-user presses the switch.
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