Tektronix 222 Operator's Manual page 55

222 DSO Operators-How It Works
Wronk 222
Dlgnal storage
oscilloscope
4.1 2
SECIDIV SCALING
SECIDIV
Rotate the
0
knob (outer knob of the two concentric Hori-
zontal Control knobs) to set the horizontal time scaling (seconds
per division).
The range steps are in a 1-2-5 switching sequence from 50 ns per
division to 20 sec per division. With the X I 0 MAG feature on, the times
per division decrease by a factor of 10 (5 ns per division to 2 sec per
division). The SECIDIV switch setting is displayed in the bottom line
of readout and changes with knob rotation until either range limit is
reached. Continuing to turn the knob past the range limit causes no
further readout change.
At some frequencies the display may be aliased. An alias waveform
is one that is formed by under sampling. The sampling rate at a par-
ticular SECIDIV setting is too low to capture enough data points to
define the signal period. The result is a waveform display composed
of samples taken from different periods of the signal. An indication
that a waveform may be an alias is an unstable display that cannot be
stabilized by adjusting the Trigger LEVEL control. Increase the
SECIDIV setting to eliminate the alias.