termination of 110 Ω on the AES/EBU XLR input and 75 Ω on the
SPDIF/EIAJ BNC input. The LoZ impedances are required by the
interface specification, so they should generally be used unless
another device connected in parallel with the test instrument is
providing termination.
The digital input will come from whichever of the digital input
connectors has an active signal on it. Only one digital input signal
should be connected at any time.
The lower right soft key controls the detector for the jitter display. The
PEAK selection will use a peak detector to measure the jitter and
display the peak value of the jitter. The RMS selection will use an
RMS detector to measure the jitter, and then calculate the equivalent
peak value assuming that the jitter signal is sinusoidal (the
‘peak-calibrated RMS value’ of the jitter).
The lower left soft key selects between ‘UN-WTD’ (unweighted) and
‘SELECTIVE’ measurement types. The unweighted selection applies
no extra filtering to the jitter signal. The SELECTIVE option applies a
narrow bandpass filter to the jitter signal before measurement. The
tuning of the filter is shown in the top right corner of the display and
may be adjusted using the FREQUENCY controls. This can be used
for manual spectrum analysis by adjusting the tuning to find the
highest-amplitude components in the jitter.
The RMS detector should always be used with the SELECTIVE filter.
This is because the filter reduces the signal to almost a pure sinusoid,
the peak value of which is not directly related to the peak value of the
jitter on the interface. The RMS detector also reacts to changes more
quickly than the PEAK detector.
IMPORTANT NOTE: All jitter amplitudes are calibrated in
peak values on the ATS-1 Dual Domain. This differs from
some other instruments which may generate and measure
jitter calibrated in peak-to-peak values. The peak value is
generally half of the peak-to-peak value.
4 Functions
Jitter Function Descriptions
4-40 ATS-1 Dual Domain User's Manual
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