Tektronix SPG8000A, User Manual

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SPG8000A User Manual 135
Mainframe diagnostic
Readouts
Figure 46 shows sample diagnostic readouts for the Mainframe. The readouts are
grouped into sections for general diagnostics, power supply diagnostics, and Main
board voltages.
Figure 46: Mainframe diagnostic readouts
General mainframe diagnostic readouts :
•
Tune
: This readout displays how far the instrument is deviating from the
calibrated internal frequency of the internal oscillator to lock to an external
reference input. One value of this readout is to determine if the instrument
oscillator needs to be calibrated. If the instrument is locked to a traceable
reference, then any tune value indicates error in the instrument calibration.
The first part of the readout indicates the fractional amount of deviation
from the calibrated frequency. For example, if you use a reference signal to
lock to a video source that is 5 parts per million high, then the readout will
say “+5.00e - 6”. This allows you to measure the frequency of the reference
input and to see if the input is near the end of the available tuning range. If
the instrument is in internal reference mode, the tune value should be 0.00
e- 6 and the integer values will equal the Calibration value readout.
Note: The display show s non- zero deviation values only when the signal reference
source is not configured as Internal in the Reference menu.
The integer values indicate the actual tuning control word. The allowed
range of the tuning control word is 0 to 4,194,304. The first num ber is the
current value of the word and the second number is the target value for the
tuning control loop. In most cases, these two values are the same.
However, in the case where the instrument needs to make a large