Audio Precision Portable One Plus Access User Manual

IMD
The IMD measurement function is selected by pressing the FUNCTION
IMD button. It is only available if the Intermodulation Distortion
Option is installed. The Portable One Plus Access can be purchased
with or without this option, or the option can be added at a later time.
The IMD measurement conforms to the SMPTE and DIN testing
standards. These standards call for a low-frequency tone to be mixed
with a high-frequency tone at a 4:1 amplitude ratio. The signal is then
sent through the device-under-test. Next the low-frequency tone is
filtered out and the high-frequency tone is sent through an AM
demodulator. After bandwidth-liming to 700 Hz, the demodulated
signal is measured. This is the intermodulation distortion. It is
measured as a percentage or dB difference between the amplitudes of
the high-frequency tone and the demodulated remainder.
Figure 4-24. Main Panel in IMD Function
GENERATOR
MONITORS
B
A
INPUT
RANGING
INPUT
TERMINATION
INPUT
TERMINATION
LCD DISPLAY
SECONDARY
READING
DETECTOR
INTERNAL
JUMPER
INPUT
MONITOR
SPEAKER/
HEADPHONE
READING
MONITOR
CHANNEL A
CHANNEL B
PRIMARY
READING
DETECTOR
IMD
DEMODULATOR/
FILTER
Figure 4-25. Block Diagram of IMD Measurement
4
Operation
Controlling the Analyzer : IMD Operation
Portable One Plus Access User's Manual 4-43
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Audio Precision Portable One Plus Access Specifications

General

Brand	Audio Precision
Model	Portable One Plus Access
Category	Test Equipment
Language	English