The circuit in an experimental setup is typically called the experimental circuit.

However, depending on the specific experiment and context, it might also be referred to as:

* Test circuit: Emphasizes the purpose of evaluating or testing a component or phenomenon.

* Measurement circuit: Highlights the focus on obtaining data or measurements.

* Demonstration circuit: When the primary goal is to showcase a principle or concept.

* Prototype circuit: If the setup is a preliminary version of a larger, more complex system.

The specific term used can vary depending on the field of research, the nature of the experiment, and the preferences of the researchers.