Connectors such as plugs and sockets are a type of cold end termination. They are a method to connect your sensors to your instrumentation. Plugs are connected to your sensor, and sockets would be attached or apart of your instrumentation. There are two common types of plugs and sockets that are industry standards. The larger type is called a standard connector and it comes with round pins, the small connector is called a miniature connector and it has flat pins. They are designed so they can only be connected when the pins are polarised the correct way to ensure cross-connection is impossible.
Thermocouple connectors utilise thermocouple alloys so that no errors are generated from the connection. As such, each thermocouple connector will only work with its designated thermocouple type. Resistance thermometer connectors come with three pins instead of two pins.
Plugs are sockets come in a variety of materials including plastic, high temperature plastics and very high temperature ceramics.