Probe Compensation; Applications - Tektronix T921 Instruction Manual

3 . Set the INTENSITY and FOCUS controls for the
best defined display. If the display still appears out of
focus, use a small screwdriver to adjust the ASTIG control
(through left cabinet side of T921/T922) for the best
defined display.
4. Rotate the INTENSITY control fully clockwise. The
display will get brighter and defocus (get thicker) . Return
the INTENSITY control to the preferred brightness level .
Ext Z Axis Input Operation
Forthe T921 orT922 a positive-going signal will cause a
decrease in intensity, and a negative-going signal will
increase the intensity level of a low-intensity trace. For the
T922R, an internal plug allows a selection of either a
positive-going or a negative-going signal to cause a
decrease in intensity. See Service Information .
X1410 and Trigger Operation
1 . Note a display with several cycles of the PROBE
ADJ waveform . Rotate the X1-X10 control fully clockwise
to X10 and note that only one cycle is visible. Return
control to X1 .
2 . Set the SEC/DIV to .1 ms . Position the start of the
display (left-hand edge) on the screen . Set the SLOPE
button to +OUT position . Rotate the LEVEL control
through its range. The start of the display will move along
the positive (rising) slope of the signal until the display
becomes unstable .
3 . Set the LEVEL control for a stable display that starts
at about the middle of the slope.
Now set the SLOPE button to -IN position . Rotate the
LEVEL control through its range. The start of the display
will move along the negative (falling) slope of the signal
until the display becomes unstable .
4. Set the LEVEL control for a stable display that starts
at about the middle of the slope .
5. Set the MODE switch to NORM . The display should
start on the negative slope. In the NORM mode the display
will disappear if the LEVELcontrol is improperly adjusted .
6. Set the SLOPE button to +OUT position . The
display should start on the positive slope.
7. Disconnect the probe from the instrument . Set the
CH 1 AC-GND-DC switch to GND . The trace should
disappear.
REV . B JUL 1977
Example:
Operating Instructions-T921/T922/T922R
8 . Set the SOURCE switch to LINE . If a trace doesn't
appear, adjust the LEVEL control until a trace appears.
9. Set: SOURCE
INT
MODE
AUTO
CH 1 AC-GND-DC
AC
The instrument is now ready to operate when signal is
applied to the CH 1 input .
PROBE COMPENSATION
An incorrectly-compensated probe is one of the
greatest sources of operator error. Most attenuator probes
are equipped with adjustments to ensure optimum
measurement accuracy .
Some probes are compensated by using a small,
insulated screwdriver through an access hole to the .
compensation adjustment . Other probes may have an
adjustment system similar to that shown in Fig . 2-10 .
Probe compensation is accomplished as follows:
Set the appropriate VOLTS/DIV switch to .1 V, the AC-
GND-DC switch to DC, and the SEC/DIV switch to 2 ms .
Connect the probe to the vertical input and touch the
probe tip to the PROBE ADJ connector . Notice a display
similar to those shown in Fig . 2-11 . Adjust the probe for the
correct compensation The effects of incorrect probe
compensation on three types of signals are illustrated in
Fig . 2-11 .
APPLICATIONS
Peak-to-Peak Amplitude Measurements
To measure the amplitude of a signal, multiply the
vertical deflection (in divisions) by the VOLTS/DIV switch
setting. (Use VOLTS/DIV window to match attenuation
factor of probe used .)
The display amplitude is 3 divisions (see Fig. 2-12) and
the VOLTS/DIV switch is set to .5 V. Substituting the given
values :
Amplitude =3 divisions x 0 .5 volt/division =
1 .5 V p-p
2- 13