Tektronix 7D11 DIGITAL DELAY Service Instructions Manual page 10

CONTROLS AND CONNECTORS
The major controls and connectors for operation of the
7D11 are located on the front panel of the unit. Two
controls located inside the unit for auxiliary functions are
described in the General Operating I nformation section.
The front-panel controls and connectors are identified in
Fig. 1-2; their functions are as follows:
®
GJ
COUNT MODE Switch
Selects mode of operation and clock-signal
source for Time count mode.
o
B SWEEP DELAY MODE Switch
Selects the delay mode logic for time-base unit.in
B Horizontal compartment of mainframe.
o
TRIGGER SLOPE/LEVEL Controls
Select slope and amplitude point of input signal
where the delay is initiated.
o
TRIG'D Indicator
Lights when a trigger is produced.
o
COUPLING Switch
Selects the method of coupling the input signal
to the Trigger circuit.
o
SOURCE Switch
Selects Trigger input signal source.
EVENTS START TRIGGER SLOPE/LEVEL
Controls
Select slope and amplitude point of input signal
where the Events Start count is initiated.
DELAY TIME OR EVENTS Control
Selects delay time or number of events counted.
Direction of rotation selects increase or decrease
in delay time or number of events.
RESET
Resets the DELAY TIME or EVENTS to
0000001.
FINE DELAY (ns) Dial
Selects analog delay time added to digital delay
time selected by DELAY TIME OR EVENTS
control.
Operating Information-7D11 Service
G2J
DLY'D TRIG OUT
BNC connector for Delayed Trigger output
signal.
(g]
EXT 1 MHz IN or EVENTS START TRIG IN
BNC connector for input of external 1 MHz
time·reference signal or input of Events Start
Trigger input signal. Connector function is deter-
mined by setting of COUNT MODE switch.
~
DLY INTERVAL OUT
BNC connector for Delay I nterval output signal.
[!;]
EXT TRIG IN
BNC connector for external input to Trigger
circuit (selected by SOURCE switch in the
external positions).
GENERAL OPERATING INFORMATION
Signal Connection
In general, probes offer the most convenient means of
connecting signals to the 7D11 external trigger inputs.
Tektronix probes are shielded to prevent pickup of electro-
static interference. A 10X attenuation probe offers a high
input impedance and allows the circuit under test to
perform very close to normal operating conditions. Also, a
10X probe attenuates the input signal ten times.
Tektronix probes are designed to monitor the signal
source with minimum circuit loading. The use of a probe
will, however, limit the maximum trigger frequency range.
To obtain maximum trigger bandwidth when using probes,
select a probe capable of compensating the input capaci-
tance; observe the ground ing considerations given in the
probe manual. The probe-to-connector adapters and the
bayonet-ground tip provide the best frequency response.
In high-frequency applications, requiring maximum over-
all bandwidth, use a coaxial cable terminated at both ends
in the characteristic impedance of the cable. To maintain
the high-frequency characteristics of the applied signal, use
high-quality low-loss cable. Resistive coaxial attenuators
can be used to minimize reflection if the applied signal has
suitable amplitude.
High-level, low-frequency signals can be connected
directly to the external trigger inputs with short, unshielded
leads. When this method is used, establish a common
ground between the 7D 11 and the associated equ ipment.
The common ground provided by the line cords is usually
inadequate. If interference is excessive with unshielded
leads, use a coaxial cable or probe.
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