An electron distribution function measurement system, applicable to noisy plasma environments, is presented. The system is based on the harmonic differentiation technique, which utilizes the nonlinearity of the probe current‐voltage characteristic to infer distribution function structure. Measurements couple low noise, phase sensitive detection with digital data acquisistion and analysis, resulting in fast and accurate measurement in noisy environments where active electronic differentiation may prove untenable. The accuracy of the experimental technique and measurement system is discussed. Using a high power arc plasma, an example demonstrating the experimental system is given.