Base metal thermocouple assemblies are designed to be used in the most severe and demanding environments. The choice of a specific style is to a large degree determined by the temperature working range, ambient atmospheric or media conditions, as well as the size and shape required for the application. Control requirements such as accuracy and speed of response may also be considerations.

When speed of response is critical, specify the open end construction. An exposed element is directly subject to corrosion and physical damage; therefore, this style should be used only after consideration of the relative need for fast response versus thermocouple life.

Another feature for improving response time is the butt welded junction. This design has less mass and therefore faster response that the twist, which is normally supplied by the factory. The twist weld offers greater mechanical strength and longer life.

When possible, the sensor should be installed in a vertical plane rather than horizontal to prevent sagging.