Trigger Source; Trigger Slope/Level; Events Start Trigger - Tektronix 7D11 Instruction Manual

The triggering point in the AC position depends upon
the average voltage level of the input signal. If the input
signal occurs randomly. the average voltage level will vary.
causing the triggering point to vary also. This shift of the
triggering point may be enough so it is impossible to
maintain a stable delay start; in such cases, use DC
coupling.
AC IF REJ. In this poSition. DC is rejected and
low-frequency input signals below about 30 kilohertz are
attenuated. Therefore, the delay is triggered only by the
higher-frequency components of the input signal. The AC
lF REJ position is particularly useful for providing stable
triggering if the input signal
components.
AC HF REJ. This COUPLING switch position passes
all low-frequency signals between about 30 hertz and 50
kilohertz. DC is rejected and signals above 50 kilohertz are
attenuated. This position is useful to trigger the delay from
the low-frequency components of a complex waveform.
The DC position can be used to provide stable
DC.
triggering from low-frequency or low-repetition-rate signals
which would be attenuated in other modes. It can also be
used to trigger the delay when the input signal reaches a DC
level selected by the setting of the SLOPE/LEVEL control.
When triggering from the internal source, the setting of the
vertical unit position con trolls) affects the DC triggering
point.

Trigger Source

The TRIGGER pushbuttons located below the SOURCE
title select the source of the signal connected to the Trigger
circuit.
INT.
In this position, the input signal is derived from
the associated vertical unit. Therefore, the 7Dl1 must be
installed in a horizontal oompartment to use the internal
source. Further selection of the internal signal may be
provided by the vertical unit and mainframe; see the
instruction manuals for these instruments for further
information.
LINE. In this SOURCE switch position, a sample of the
power-line voltage from the mainframe is connected to the
Trigger circuit. line triggering is useful when the input
signal is time related (multiple or submultiplel to the line
frequency. It is also useful for providing stable triggering
from a line-frequency component in a complex waveform.
®!
contains line-frequency
REV. JAN 1974
Operating Inltructions-7Dl
EXT_ A signal connected
connector can be used to trigger the delay in the EXT
position of the SOURCE switch. An external signal can be
used to provide a trigger when the internal signal amplitude
is too low.
EXT +10. Operation in this position is the same
described for EXT except the external signal is attenuated
10 times. Attenuation of high-amplitude signals is desirable
to extend the range of the LEVEL control.

Trigger Slope/Level

The TRIGGER SLOPE/LEVEL oontrols determine the
slope and voltage level of the input signal where the Trigger
circuit responds. Generally, the best point on a waveform
for triggering the delay is where the slope is steep, and
therefore usually free of noise. Assuming a sine-wave input
waveform, the steepest slope occurs at the zero·crossing
point. This is the point selected for triggering when the
LEVEL control is set to 0 (canter). A more positive or
negative point on the waveform is selected as the LEVE L
control is rotated clockwise or oounterclockwise respec­
+
tively from 0 (towards or - symbols on panel).
Before setting the TAIGGER
SLOPE, MODE, COUPLING, and SOURCE should be
selected. Then adjust the LEVEL control so the delay starts
from the desired point.

Events Start Trigger

The Events Start Trigger is used in the EVENTS count
mode to differentiate between the event that starts the
delay and the events being counted.
The EVENTS START TRIG IN connector provides the
input to the events·start signal. The EVENTS START
TRIGGER SLOPE and LEVEL controls select the ampli­
tude point and slope on the input signal where the delay is
triggered.
Generally, the best point on a waveform for triggering
the delay is where the slope is steep, and therefore usually
free of noise. Assuming a sine-wave input waveform, the
steepest slope occurs at the zero-crossing point. This is the
point selected for triggering when the LEVEL control is set
to 0 (center). A more positive or negative point on the
waveform is selected as the LEVEL control is rotated
clockwise or counterclockwise respectively from 0 (towards
+
or - symbols on panel).
1
Operators
to the EXT TAIG IN
as
LEVEL, the desired
'-5