Tektronix 7D14, Instruction Manual

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Operating Instructions—7D14
Fig. 2-7. Counting the number of pulses within a burst.
2. Install the 7D14 in a vertical plug-in compartment.
3. Connect the input signal to the CH A INPUT and
amplifier unit input connectors via a BNC T connector and
short BNC cable.
4. Connect the delayed gate output to the EXT GATE
connector through a BSM to BNC male adapter (supplied
accessory).
5. Press the MANUAL GATE OFF pushbutton.
6. Turn the oscilloscope power on. Allow about 20 min­
utes warmup.
7. Advance the oscilloscope Readout and Intensity con­
trols as necessary to obtain a usable display.
8. Set the delaying time-base unit Time/Div control to
view several cycles of the input-signal waveform as shown in
Fig. 2-7.
9. Set the delaying time-base unit Delay Time Mult and
the delayed time-base Variable Time/Div controls to inten­
sify the pulses to be counted (see Fig. 2-7).
10. Set the 7D14 TRIGGER controls as necessary to
obtain a steady count.
OPERATING MODES
Counting a Displayed Signal
This mode of operation enables simultaneous counting
and CRT display of a signal. The CRT display is obtained in
the usual manner; i.e., the signal is connected to an ampli­
fier unit in a vertical plug-in compartment and a time-base
unit in a horizontal compartment provides the sweep. The
signal is routed to the 7D14 from the amplifier unit trigger
pickoff through the oscilloscope trigger source selection
circuitry. This necessitates operating the 7D14 in one of the
horizontal compartments of an oscilloscope which can
accommodate four plug-in units.
The INPUT SENS/P-P VOLTS switch selects the signal
from the amplifier unit when it is set to TRIG SOURCE.
The Trigger Source switch for the horizontal compartment
containing the 7D14 must be set to select the vertical com­
partment originating the signal to be counted. In addition,
dual-trace amplifier units contain further trigger source
selection. This must be set to select the correct channel.
Signals selected in the TRIG SOURCE position are AC
coupled which limits the low-frequency response. The high-
frequency response is limited by the bandwidth of the
amplifier unit being used.
This mode of operation is more convenient for simul­
taneous measurements than using separate probes for
counter and oscilloscope. Also, one signal connection places
less load on the circuit under test than if separate ptobes
were used. An added advantage is being able to use the
amplifier unit to amplify signals whose amplitude would
otherwise be insufficient to trigger the 7D14.
Trigger Indicator
The output of the 7D14 trigger circuit can be displayed
on the CRT, along with the signal being counted. The 7D14
controls can then be adjusted while observing the CRT dis­
play for triggering at the desired point on the waveform.
To use this mode of operation, the 7D14 must be
operated in a vertical plugnn compartment. The signal to be
measured is connected to the CH A INPUT connector and
to the input of the other vertical unit using a T connector.
The two waveforms can then be displayed by setting the
oscilloscope Vertical Mode to Alt or Chop.
The "Trigger Indicator" is a rectangular waveform dis­
play with a nominal amplitude of 0.2 division peak-to-peak.
Proper triggering is indicated when the "Trigger Indicator"
waveform matches the signal waveform frequency and duty
cycle as shown in Fig. 2-8.
The Trigger Indicator display vertical position is set to
the CRT center at the factory. However, the display can be
positioned for the convenience of the operator with the
internal Display Pos adjustment R866 (see Fig. 2-2). To
make this adjustment, use the following procedure:
1. Remove the Indicator Oscilloscope left cover and the
7D14 left side shield.
2-10