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

Chapter 3: Testing Performance

Time Scale Accuracy (TSA)

Time Scale Accuracy (TSA)
This procedure verifies the maximum TSA specification for the oscilloscope.
Description
TSA refers to the absolute accuracy of oscilloscope's time scale. Because TSA depends directly on
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.
Equipment Required
Equipment Critical Specifications
Output Frequency: ≥ 10 MHz
Synthesized sine wave
source
Output Amplitude: 0 dBm
Frequency Resolution: 0.1 Hz
10 MHz frequency Output Frequency: 10 MHz
reference
Output Amplitude: 0 dBm
Absolute Freq. Error: < ±0.01 ppm
SMA cable 50 ohm characteristic impedance
SMA (m) connectors
Max Frequency: ≥ 50 MHz
RF cable 50 ohm characteristic impedance
BNC (m) connectors
Max Frequency: ≥ 50 MHz
Adapters, assorted 3.5 mm (f) to Precision BNC (m)
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