Tektronix 1S1 Instruction Manual page 92

Fig. 5-33. Adjustments on left side of Type 1S1 for loop gain, bridge standoff and risetime.
19. Adjust Bridge Standoff
a. Substitute a 2X attenuator for the 5X attenuator in the
signal connection from the pretrigger pulse generator to the
Type 1S1 SIGNAL IN connector.
b. Set the Type 1S1 TRIGGER SENSITIVITY control to pro-
duce a triggered (1-trace) display.
c. Reset the following test oscilloscope controls:
Time/Cm
Input Atten
Input Coupling
Millivolts/Cm
d. Connect the test probe to the Type 1S1 VERT OUTPUT
jack.
e. Trigger the test oscilloscope display.
f. Adjust the Type 1S1 SAMPLES/CM and TIME POS-
TION controls to produce a display similar to Fig. 5-34A on
the crt of the test oscilloscope.
g. Position the baseline of the displayed pulse 2 cm below
the center of the test oscilloscope screen.
h. Increase the pulse amplitude into the Type 1S1 with
the variable attenuator until the baseline immediately fol-
lowing the pulse in the test oscilloscope display begins to
rise. (See Fig. 5-34B).
i. Back off on the pulse amplitude to the point where
the baseline just started to rise.
5 mSEC
1
Dc
50
j. Check the test oscilloscope waveform for an amplitude
of 2 volts or more (4 cm or more).
k. If the pulse amplitude is less than 2 volts:
1. Adjust the variable attenuator for a display ampli-
tude of 2.2 volts (4.4cm) on the test oscilloscope screen.
2. Adjust R22 (BRIDGE VOLTS) counterclockwise slowly
until the baseline immediately following the pulse (Fig.
5-34B) stops moving downward.
It is suggested that the bridge voltage not be set
excessively high, since random noise of the system is
increased by this adjustment.
3. Recheck the standoff voltage as in steps g through
above.
4. Disconnect the input signal temporarily.
5. Readjust R30 (BRIDGE BAL) as described in step 15.
6. Reconnect the pulse signal to the Type 1S1 SIGNAL
IN connector.
7. Readjust loop gain as described in steps 18 p
through 18 v. (This can be done with the 2X attenuator
with overshoot on the leading edge, or the 5X attenuator
may be substituted temporarily.)
8. Connect the test probe to the Type 1S1 VERT OUT-
PUT jack again.
Calibration – Type 1S1
NOTE
5-29