Operating
Instructions
—7D14
7.
The readout
display should read 1000.0000 kHz ±1
count (999.9999
to
1000.0001 kHz).
8.
Check
that
the GATE indicator light is on during the
time the 7D14 is
counting (10 seconds).
9.
Sequentially
press the MEASUREMENT INTERVAL
1
s through 1 ms pushbuttons and check that the display
corresponds to the readings given in Table 2-1.
OPERATING CHECK DISPLAY
TABLE 2-1
MEASUREMENT
INTERVAL
READOUT
LIMITS
UNITS
MINIMUM
MAXIMUM
10 s
999.9999
1000.0001
kHz
1
s
999.999
1000.001
kHz
100 ms
0.99999
1.00001
MHz
10 ms
0.9999
1.0001
MHz
1
ms
0.999
1.001
MHz
10.
Disconnect the cable and the adapter.
GENERAL
OPERATING
INFORMATION
Signal Connection
In
general,
probes offer the most convenient means of
connecting
signals
to the 7D14 CH A INPUT.
Tektronix
probes are
shielded to
prevent pickup of electrostatic inter
ference.
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 bandwidth capability of
the
7D14. To obtain maximum
bandwidth when using
probes,
use
a probe capable of compensating 20 pF; use one
of
the 1 MΩ input impedance positions
of the INPUT
SENS/P-P VOLTS
switch; and observe the grounding
con
siderations
given
in
the probe
manuals. 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 for the signal connection
and
a
50
Ω input impedance
position of the INPUT
SENS/P-P VOLTS
switch. To
maintain the high-frequency
characteristics of the applied
signal,
use high-quality, low-
loss
cable.
Resistive attenuators can
be used to minimize
reflections
if the
applied
signal has suitable amplitude.
A
signal can
also be routed to the 7D14 through an am
plifier
unit in a vertical
plug-in compartment via the internal
trigger
pickoff circuitry of the
Indicator Oscilloscope. This
method of
signal connection minimizes circuit loading
for
measurements
requiring simultaneous counting and
CRT
display (see
Counting a Displayed Signal).
General Control
Settings
Introduction.
The
following discussion provides control
setup
information
for general measurement applications.
Further information
can be found under Controls and Con
nectors
or in the
discussion for a specific
measurement
mode (e.g.,
Frequency
Measurements).
Trigger Controls.
Signals
to be counted may have
a wide
variety of
shapes and amplitudes, many of which are unsuit
able to
drive the
counting circuits. For this reason, the
signals are
first applied to signal
conditioning circuits; then
to
the trigger circuit, where they are converted to rectangu
lar pulses
of uniform amplitude.
Signals
often
have characteristics which would prevent
triggering
or result
in
an erratic count. These signals must
be
conditioned before they are applied to the trigger input.
The
INPUT SENS, COUPLING, and BW switches provide
means
of
conditioning the trigger signal. Obtaining a
steady,
reliable
reading is
dependent upon the
proper setting of
these
controls and
proper
adjustment
of the LEVEL/
SLOPE
control.
The
INPUT SENS/P-P VOLTS switch
selects either inter
nal
routing of the signal
from the Indicator Oscilloscope
trigger circuitry
or connection through the CH
A INPUT
connector.
Operation in the TRIG SOURCE position
requires
that the 7D14 be installed
in
a horizontal plug-in
compartment.
The oscilloscope
Trigger Source switch for
that
horizontal
channel then
provides
further selection of
the signal
source.
(For more information on
this mode of
operation,
see Counting a
Displayed
Signal.)
For signals connected to the CH A INPUT connector, set
the
INPUT
SENS/P-P VOLTS
switch
to select the desired
input
impedance. An input impedance of 50 Ω should be
used
when coupling into a 50-ohm system for high-
frequency
measurements. The 1 MΩ settings provide a
higher input
impedance
for
minimizing loading on the
signal
source.
Select a P-P VOLTS
setting appropriate to the amplitude
of the
signal
being measured. The P-P VOLTS figure on the
front panel indicates
the
minimum signal amplitude which
will
produce a count. The best P-P
VOLTS setting is one
that
is much
larger than the largest
noise signal anticipated,
®i
2-5
Summary of Contents for 7D14
Page 4: ...7D14 ...
Page 11: ...Operating Instructions 7D14 Fig 2 1 7D14 front panel controls and connectors 2 2 ...
Page 33: ... 3 13 Fig 3 11 Logic diagram for Zero Cancel Logic stage Circuit Description 7D14 ...
Page 38: ...3 18 Fig 3 16 Time Base and Control circuit detailed block diagram Circuit Description 7D14 ...
Page 44: ...NOTES ...
Page 46: ...NJ Fig 4 1 Electrode configuration for semiconductors in this instrument I ...
Page 68: ...NOTES ...
Page 96: ... 7DI 4 DIGITAL COUNTER UNIT ...
Page 98: ...GRS 0371 BLOCK DIAGRAM ...
Page 99: ......
Page 103: ...0 0 I 200 mV 500 µs 0 001 200 mV 500 µs 0 001 MHz 00 mV E 00 µs 0 001 MHz ...
Page 106: ...1 ...
Page 110: ...A2 Logic Circuit Board Assembly jQ798i 798 jc743 CR744t uni R724 R742 JL744S FrR796 ...
Page 113: ......
Page 114: ...P 0 A2 LOGIC BOARD ...
Page 121: ... A B D t F H J NPR Tj ZWX V A AC M AEA HUM qAZ DEF HJ N P R S T J V V7X y ABM APAI AA 7DI4 ...
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Page 130: ...4 7D14 DIGITAL COUNTER ...