The effect of receiver performance and sensor choice on the determination of electrical parameters at plasma relevant frequencies and impedances is studied. Measurements with a directional coupler based probe and voltage and current based probe are received using a vector network analyzer, power meter, vector voltmeter, and digital storage oscilloscope. Errors in reflection coefficient magnitude, impedance, and delivered power are determined as a function of the measurement system. Power errors are summarized by average errors at a load voltage standing wave ratio (VSWR) of 50, corresponding to typical conditions in low pressure parallel plate discharges. In order to effectively evaluate sensor and receiver performance, all experiments are performed at very low powers using test loads built from standard circuit elements. Representative power error at a load VSWR of 50 is found to vary from less than #1# for a directional coupler received by vector network analyzer, to nearly #125# wi..