Abstract: A dual purpose electronic instrumentation device for teaching the principles of electricity and electronics and for testing electrical systems is disclosed which includes a housing, having electronic circuitry arranged within it with control, display and terminal elements extending externally of the housing. The housing is divided into at least two portions with a first portion being movable relative to the second portion to expose or conceal a display surface having a receptacle for receiving one or more plug-in circuit cards, wherein the control, display and terminal elements of the housing and the receptacle of the display surface are interconnected with the electronic circuitry for testing electrical systems which are electrically coupled to the terminal elements and the receptacle. When the display surface is concealed, the instrumentation device is for testing electrical devices electrically coupled to the terminal elements of the housing.