Tektronix 222 Operator's Manual page 85

Making Measurements-222 DSO Operators
Again, as with the voltage measurement, accuracy is improved by
positioning the waveform to take advantage of the minor divisions of
the center horizontal graticule line.
For example, in Figure 5-3 the horizontal spacing for one sine-wave
period is 8.2 divisions with a SECIDIV readout of 1 ms. Multiplying 1
ms times 8.2 divisions gives a period of 8.2 ms.
RISETIME MEASUREMENT. Using the graticule to measure the rise
time or fall time of a signal requires some signal scaling so that the
10% and 90% dotted graticule lines may be used for making the
measurement. Basically, the scaling involves selecting a VOLTIDIV
setting that produces more than the required 6 division of veFtical
deflection, then adjusting the Variable VOLTSIDIV control to set the
deflection for exactly 6 divisions. The signal is positioned vertically to
set the baseline and peak amplitude of the signal as shown in Figure
Figure 5-4. Rise Time measurement.