Tektronix 2246 Operator's Manual page 57

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Leb A
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7. Align the measurement point as displayed by the B
delayed trace with the center vertical graticule line. The
center line then becomes the measurement reference point
for making the time difference measurement.
8. Note the delay-time setting in the upper line of crt
readout.
9. Now position the intensified zone to the second
measurement point, and again align the point displayed on
the B delayed trace with the center horizontal graticule
line.
10. Note the second delay-time setting. Subtract the
first setting from the second setting to determine the time
difference.
ATIME DELAY MEASUREMENT
In the A Horizontal MODE, the time cursors that appear
when the measurement mode is enabled are exactly the
"same as those that are seen for the CURSORS measure-
ment mode, and the measurement choices are the same.
Refer to CURSORS MEASUREMENT for their use. When
in ALT or B Horizontal MODE, the ATIME measurement
mode provides two intensified zones on the A Intensified
trace. There are also two associated B delayed traces
matching the intensified zones. A direct readout of the
delay difference between the two zones is displayed in the
top line of crt readout. Use the following procedure steps
as a guideline for making ATIME delay-time measure-
ments.
1. Apply the signals that measurements are to be
made on to the vertical input connectors. Turn on the
VERTICAL MODEs needed to display the signals.
NOTE
Probes are the most convenient for in-circuit testing,
and coaxial cables are the most convenient when
using signal generators as the source of the test sig-
nals. Use correct terminations to match the output
impedance of any signal generator used. The CH 1
and CH 2 vertical channels provide the widest range
of signal conditioning, and the CH 3 and CH 4 verti-
cal channels are most useful for digital signal levels.
REV APR 1987
Measurement Processes and Applications—2246 Operators
2. Use a VOLTS/DIV setting that produces a usable
vertical display amplitude for viewing ease; use an A
SEC/DIV setting that produces two to five repetitions or
cycles of the signal across the graticule area.
NOTE
When viewing multiple traces, it is best to limit the
vertical amplitude to about two divisions so that
good trace separation may be obtained in the
display.
3. Switch the Horizontal MODE to ALT. Advance the
SEC/DIV setting at least one position to obtain a faster B
SEC/DIV setting. This activates the B Sweep and expands
` the intensified portion of the A Sweep trace.
Yy
4. Press the ATIME button, then select the l- SEC +I
menu choice. This produces two intensified zones on the
A Sweep trace and two alternate B Delay Sweeps. Use
the TRACE SEP and VERTICAL POSITION controis to
position the B Delay Sweeps vertically in the graticule area
for ease of viewing the separate traces.
5. Use the SET MEAS'MT CHANNEL menu choices to
seiect the desired channels to make the time measure-
ments on.
NOTE
When making delay measurements between two
different signals for time or phase difference, the
SET MEASMT CHANNEL choices must be set to
the correct measurement source channel to obtain
the desired measurement results. BOTH delays must
be set to the same channel source for making
period, pulse width, or rise-time and fall-time mea-
surements. If only a single channel is selected for
display, both delays will default to that channel. If a
channel is selected as a measurement source, it will
be turned on if not already on; but it will not be
turned off when deselected as a measurement
source. Extra display channels must be turned off
using the VERTICAL MODE buttons. If a channel is
displayed but not selected as a measurement
source, that waveform trace will not be intensified,
and no alternate B Delayed trace will be displayed
for that channel.
6. Using the center horizontal graticule line as a refer-
ence point, set the reference delay to align the point of
interest to be measured (point A in Figure 6-15) from to
that reference point with the l- OR DELAY control. Set the
A delay to align the second point of interest, displayed in
the second B Sweep {point B in Figure 6-15), to the refer-
ence point using the ~| OR A control. The measured