Time Scale Accuracy (Tsa) Test - Keysight Infiniium 9000 Series Service Manual

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Testing Performance
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Time Scale Accuracy (TSA) Test

This procedure verifies the maximum TSA specification for the oscilloscope.
Description TSA refers to the absolute accuracy of an oscilloscope's time scale. Because TSA
depends directly on the frequency of a crystal oscillator, it is comprised of two
components: an initial accuracy component and an aging component.
The initial accuracy component applies to the oscilloscope's accuracy immediately
after a calibration, whether performed at the factory, by a customer, or by a
Keysight service center. The aging component scales linearly from the time since
the last factory calibration and adds to the initial accuracy component.
Specifications TSA is published as a warranted specification, expressed by the following formula.
The aging component is specified by the crystal manufacturer while the initial
accuracy component represents our best estimate of the final value, which will be
determined from subsequent characterization of a large sample of production
units.
TSA = ±(0.4 + 0.5(Years Since Factory Calibration)) ppm peak
To see the number of years since factory calibration, open the oscilloscope
application and navigate to Utilities > Calibration in the top menu bar. Inside this
dialog box will be a line specifying the Time Scale Cal Date. This is the date of the
last factory calibration.
Note that TSA is specified with respect to an absolute standard and therefore its
measurement results must be compared against test limits that account for the
uncertainties in its measurement results. The total measurement uncertainty of the
following test procedure is 0.1 ppm. It is the sum of 0.01 ppm for the test signal's
absolute frequency accuracy, 0.04 ppm for the voltage noise and phase noise of
the oscilloscope's digitized waveforms, and 0.05 ppm for the residual settling time
of the crystal oscillator after the specified 30 minute warm-up time. Therefore, all
measurement results need to be better than the specified values by a test margin
of at least 0.1 ppm in order to guarantee compliance to the specification.
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Move the splitter to channel 4 and change the scope configuration as follows.
Ensure Channel 4 is displayed and all other channels are turned off.
a
Set the vertical scale of channel 4 to 5 mV/div.
b
Set the horizontal scale to 16 ns/div (to display 8 cycles of a 50 MHz
c
waveform).
Click on the V rms measurement at the bottom of the screen. When the V
d
rms setup window appears, change the source from Channel 3 to Channel 4.
Repeat steps 7 to 20 to complete measuring gains for channel 4.
Infiniium 9000 Series Oscilloscopes Service Guide