The 339A Distortion Measurement Set lets you measure like a pro with this complete measuring system. With the 339A you get a total Harmonic Distortion Analyzer, True RMS Voltmeter, and Sine Wave Oscillator. This unit allows THD measurements as low as 0.0018% over a 10Hz to 110kHz frequency band including harmonics to 330kHz. Distortion measurement range is 0.01% to 100% full scale (-80 dB to 0 dB) in nine ranges. The oscillator has a frequency range of 10Hz to 100kHz in four overlapping decade ranges. The output level is variable from less than 1 mV to greater than 3 V rms into 600 ohms with 10 dB/step level control and 10 dB vernier adjustment. Voltmeter range is 1 mV to 300 V RMS full scale (-60 dB to +50 dB full scale, meter calibrated in dBV and dBm into 600 ohms).