A non-linear test load is provided for calibrating a plasma system. The test load is a substrate for modeling the electrical characteristics of the plasma such that multi frequency testing can be performed in the absence of a plasma reaction. An exemplary substrate includes a first semiconductor junction for providing a non-linear response to the multi-frequency RF source provided from the anode. The first semiconductor junction exhibits a first capacitance for modeling a first plasma sheath of the anode. A plasma component is responsive to the first semiconductor junction and exhibits a resistance for modeling a resistance of the plasma, an inductance for modeling an inductance of the plasma, and a gap capacitance for modeling capacitance of the plasma. A second semiconductor junction is responsive to the plasma component for providing a non-linear response to the multi-frequency RF source provided from the plasma component, the second semiconductor junction exhibits a second capacitance for modeling a second plasma sheath of the cathode.