How is isolation specified?

The isolation characteristics of an isolator are specified in a variety of manners, including:

The degree to which an isolator successfully insulates one side of an isolation barrier from high voltages on the other side is commonly described by the isolator's isolation rating and by its maximum working voltage (or rated mains voltage). In addition, the degree to which an isolator continues to correctly transfer a signal across an isolation barrier in the presence of a common-mode transient is described by its transient immunity (or common-mode rejection). Each of these three parameters is described below.