The upper left corner of the display shows the IMD reading. The units
may be selected from % or dB by pressing the top left soft key. The
upper center of the display shows the amplitude of the signal before
filtering. Pressing the top center soft key selects the units.
The IMD generator waveform is automatically selected when entering
IMD measurement function. You may then change the generator
waveform if desired, but this will result in an invalid IMD reading.
When exiting IMD measurement function, the generator waveform is
changed back to sine.
The generator amplitude can be adjusted using the AMPLITUDE
controls, but changing the tone frequencies requires the Generator
Only Panel. Press the INSTRUMENT MODE PANELS button several
times, until you reach this panel:
The generator IMD tones can be changed from this panel. The two
generated tones are shown in the area of the panel where the
generator frequency is normally shown. The low-frequency tone is
shown on the left, separated by a slash from the high-frequency tone.
To change the low-frequency tone, press the lower right soft key. This
will select among 50 Hz, 60 Hz, 70 Hz and 250 Hz tones. To change
the high-frequency tone, press the upper right soft key. This will select
between 7 kHz and 8 kHz tones.
Frequency sweeps are not available in IMD mode since the standards
define a fixed set of frequencies. Amplitude sweeps are supported.
Although the SMPTE standard calls for a signal with a 60 Hz lower
tone and a 7 kHz upper tone, experience suggests that the lower tone
should not be a multiple of the line frequency, which in many areas is
60 Hz. Under the DIN standard, a 250 Hz lower tone with an 8 kHz
upper tone is a better choice.
& For more
information on
navigating among
the panels, see
page 3-3.
Figure 4-25. Generator only panel with IMD selected
4 Functions
Function Descriptions IMD
ATS-1 Dual Domain User's Manual 4-27
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