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9.4
Auto-callbratlon
Figure 9.3
As described in Section 2.5, the 9400A calibrates its time interpolator
relative to the internal 100 MSz crystal-controlled clock generator
every time the time base is modified by front panel operation or by
remote control.
The vertical gain and offset of an input channel are calibrated by
means of a very stable internal 12-blt digital-to-analog converter
every time the fixed gain control of this channel is modified.
Calibration of both channels also takes place whenever the bandwidth
limit is changed.
These calibrations are necessary largely because of drifts caused by
temperature changes which could arise if the 9400A is left in the same
state for a very long time. To avoid measurement errors due to
potential drifts, an internal timer of the 9400A forces a complete
auto-calibration every minute during the first I0 minutes after
power-up and every 20 minutes thereafter. This operation is transparent
to the user, but is audible due to relay switching. Note that
auto-calibration does not occur in SINGLE or SEQNCE trigger mode.
In remote control, all auto-calibration can be turned off. It may be
executed whenever
requested (see
the CALIBRATE command in
Section
7.6.6)
9-4
Getting the Most Out of Your 9400A
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