Demonstration of phase relationships in a series RLC circuit using a four‐channel multiplexer and a single‐channel oscilloscope

An effective demonstration of the phase relationships in a series RLC circuit, resonance and Q, is made possible by multiplexing four signals onto a single channel thereby converting a single‐channel scope to four channels. With the circuit explained in the text, it is possible to present a simultaneous display of V_R, V_L, V_C, and V_gen on a single‐channel scope. When the RLC circuit is excited by a variable frequency generator, V_R becomes the reference phase. The time base ramp amplitude is made independent of the generator frequency by the circuit permitting four cycles of each waveform to always be in view on the scope, even though the generator frequency is varied from approximately 800 Hz to 18 KHz.