Download 4 - Advanced Audio

Controlling the Analyzer : THD+N (Total Harmonic Distortion plus Noise)
Operation
THD+N (Total Harmonic Distortion plus Noise)
The THD+N function is selected by pressing the FUNCTION
THD+N/SINAD button.
& For more
information on
THD+N
measurement,
see the special
section on
The THD+N function uses a notch (bandreject) filter to eliminate the
fundamental frequency, and then measures the amplitude of signal
remaining. The remaining signal will contain the distortion products of
the original tone and the noise present in the signal.
Figure 4-18. Main Panel in THD+N Function
INPUT
MONITOR
INTERNAL
JUMPER
SPEAKER/
HEADPHONE
B
GENERATOR MONITORS
A
CHANNEL A
READING
MONITOR
INPUT
TERMINATION
NOTCH
FILTER
BANDWIDTH
LIMITING
FILTERS
INPUT
RANGING
PRIMARY
READING
DETECTOR
WEIGHTING
FILTERS
CHANNEL B
INPUT
TERMINATION
AVERAGING
FREQUENCY
COUNTER
SECONDARY
READING
DETECTOR
LCD DISPLAY
Figure 4-19. Block Diagram of THD+N Measurement
Portable One Plus Access User's Manual
4-25
4 Operation
This measurement is known as Total Harmonic Distortion plus Noise,
or THD+N. It is almost always displayed as the ratio of the distortion
and noise to the original signal before filtering, in units of % or dB.
Two voltmeters are used in this measurement - one to measure the
signal before filtering and another to measure the filtered signal.