GW-Instek-GAD-201G-Automatic-Distortion-Meter-GW-Instek-GAD-201G-P-The-GW-Instek-GAD-201G-distortion-meter-is-aimed-at-total-harmonic-distortion-THD-&-AC-voltage-measurement-at-audio-frequency-range-from-20-to-20k Hz-The-GW-Instek-GAD-201G-frequency-&-voltage-values-are-displayed-simultaneously-on-dual-meters-with-the-measurement-range-automatically-switching-over-full-scale-P-P-Shortcut-keys-are-provided-on-the-GW-Instek-GAD-201G-for-the-more-commonly-used-400 Hz-1k Hz-&-10k Hz