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Measuring Waveforms
3-88
CSA8000B & TDS8000B User Manual
First sampled point
Timeto firstpoint
Trigger pointof cursor
source
Horizontal divsx sec/div
+
Cursor
Cursor readout(tn) =
Horizontal Ref= 0%
Figure 3- 23: Components determining Time cursor readout values
Note that a vertical cursor readout (t1 or t2) includes and varies directly with the
time-to-first-point component, which varies directly with the horizontal position
set for the time base used by the cursor-source waveform. To see the amount of
time to the first point, press Horizontal Menu on the front panel and set
Horizontal Ref to 0% in the dialog box that displays. Now the Horizontal
position readout shows the time to first point, and subtracting this value from the
cursor readout yields the cursor position on screen relative to first point. (You
can find the horizontal readout both in the dialog box and in the control bar at
the bottom of the screen.) The following relationships hold:
Time to First Point = Horiz Position (when Horiz Ref Position is set to zero)
t1 or t2 readouts = Time to First Point + Additional Time to Cursor
Cursor Units Depend on Sources. A cursor that measures amplitude or time will
read out in the units of its source as indicated in Table 3--7. Note mixed sources
require the delta readouts to follow the units of the cursor 1 source.
Table 3- 7: Cursor units
Cursors Standard units
1
Readout names
Horizontal volts, watts, rho, ohms
v1, v2, ∆v
Vertical seconds, bits
t1, t2, ∆t
Waveform volts, watts, seconds, bit s
v1, v2, ∆v, t1, t2, ∆t
1
If the v1 and v2 units do not match, the ∆v readout defaults to the units used by the
v1 readout; if the t1 and t2 units do not match, the ∆t readout units defaults to t1
readout units.