Normally Open Contact Means

It is difficult and in some cases impossible to mix normally open and closed contacts on a single zone.

Normally open contact means. Before we get into what normally open and normally closed are let s clarify what open and closed mean. Perhaps the most confusing aspect of discrete sensors is the definition of a sensor s normal status. Normally open switch contacts are in an open state at rest. But what exactly defines normal for a switch.

Relays and contactors have two types of contacts each suited for different applications. When power is introduced an electromagnet pulls the first circuit into contact with the second thereby closing the circuit and allowing power to flow through. In other words when voltage is applied to the relay contactor terminals this contact closes. There is a common electrical connection between a contact of each pair that results in only three connection terminals.

These terminals are usually labelled as normally open common and normally closed no c nc. Normally open relays default in the open position meaning that when they re not in use there is no contact between the circuits. As with so many topics that we try to simplify by associating with something we are familiar with associating electrical current flow with water flow causes a tremendous amount of misunderstandings. Form c contacts change over or transfer contacts are composed of a normally closed contact pair and a normally open contact pair that are operated by the same device.

Normally open contacts or switches with the normally open switching function are well known in daily life such as with light switches. What is open and closed. A light switch is generally a normally open contact which on actuation closes a circuit and thus allows the current to flow to the series connected light bulb see fig. When it comes to electrical switches and contacts many people seem to be confused by the terms normally open no and normally closed nc the root of the problem seems to start with the fundamental concept of what it means to be open or closed this post attempts to clarify those concepts.

Electrical switch contacts are typically classified as either normally open or normally closed referring to the open or closed status of the contacts under normal conditions. When buying contacts look for form c spdt single pole double. Meaning pronunciation translations and examples. Normally open no contacts allow current when the relay or contactor is energized.