Promax AE-166 User Manual page 136

Operation
►
Press
Harmonic on.

Any other measurement mode will automatically be disabled.
The display splits into two screens. The top shows a bar graph with
fundamental measurement (1) and the each of the harmonic frequencies
(2 ~ 10). The bottom screen shows the amplitude, dBc and THD results.
Press Fundamental Freq.[F2] to set the fundamental frequency.
Press Number of Order[F3] to set the number of harmonic frequencies to
measure.

The number of harmonic frequencies set will affect the THD
measurement.
Press
Set the resolution bandwidth and unit for RBW Man mode.

The RBW setting will affect the THD measurement.
Mode: Auto, Man
Frequency Range(3dB): 10 kHz ~ 1 MHz (1-3-10 step)
127
> More[F7] > Harmonic[F2] > Harmonic[F1] and turn
Figure 92.
and
RBW[F4]
set the RBW to Auto or
February 2017
Man.