Operating Instructions—7D14
the total
count at the end
of the gate time or to display
each
count as it is made. Also, the 7D14 can add the counts
made
during
successive
gate times. (For further informa
tion,
see Totalize under
Measurement Modes.)
An
external gating signal can be used to control the gate
time
or measurement interval. The gating
signal is con
nected
to
the
EXT
GATE
connector
and is selected
by
pressing
the MANUAL GATE OFF pushbutton. See the
Specification
section for external gate
signal requirements.
Fig,
2-6.
(A)
Signal input
to
trigger;
shaded
area represents hysteresis
set
above noise pulses; (B) Trigger
output
with LEVEL/SLOPE
con
trol
set
in negative-slope region.
noise.
Fig.
2-5A
shows the signal with the hysteresis moved
above
the
noise with the corrected trigger output shown in
B.
Fig.
2-6A and B shows the same waveforms as in Fig.
2-5, only with
the LEVEL/SLOPE
control set in the nega
tive
slope region. Note that the trigger pulse shown in Fig.
2-6B goes positive when the signal input goes negative.
Measurement
Interval Controls.
The
MEASUREMENT
INTERVAL
switch selects
the time interval (also called gate
time)
during
which the 7D14 counts. The source of the
pulses
which
control
the
time interval determines the
measurement mode.
The
internal gate
circuits derive gate times from
a one
megahertz
reference frequency signal to make frequency
measurements.
The gate times thus derived are selected by
the
1
ms, 10 ms,
100 ms,
1
s,
and
10 s pushbuttons. The
measurement
interval selected
determines the measurement
range and
resolution.
These pushbuttons also automatically
select the
measurement
units and
decimal position in
the
display.
Table
2-2 gives the frequency range and resolution
for
each
time interval, and shows the display decimal posi
tion and
measurement units.
Generally,
use
the shorter measurement
intervals
for
high-frequency, low-resolution measurements and the longer
intervals for
measurements requiring high resolution.
Totalizing,
or counting
a number
of
events,
is accom
plished
by counting
during
a time selected
by the
MANUAL
GATE ON/OFF pushbuttons. The gate time
is
started
by
pressing the MANUAL GATE ON pushbutton,
and
stopped by
pressing the OFF button. The manual mode
is
generally used
to count
a number of events for a rela
tively
long, indefinite
time. The 7D14 can be set to display
REF
FREQ/CH B
controls.
The
INT 1
MHz pushbutton
selects
the
internal crystal oscillator
for use as a reference
signal
for
frequency measurements. The one
megahertz
signal
is
available
at the front-panel
EXT IN/MONITOR
connector when the INT
1
MHz
button
is pressed in.
When greater accuracy
is required
than is provided by
the
internal
crystal oscillator, a one megahertz external
timing
standard can be connected to the EXT IN/
MONITOR
connector. Pressing the
EXT IN pushbutton
selects the signal connected
to
the EXT IN
connector.
The
EXT IN connector and pushbutton are also used for
making
ratio measurements. The 7D14
will compare the
frequency
of the signal connected to the EXT IN connector
to the
frequency of the
Channel A signal. (For further
information,
see
Ratio Measurements under Measurement
Modes.)
Display Time
Controls.
The
DISPLAY TIME control is
used
to
set the length of time a
measurement is displayed
before
the next measurement is started. The display time
can be
varied
from at least 0.1 second to five
seconds or
longer.
The
°°
(infinite)
detent position of the DISPLAY TIME
control
sets
the
7D14 to display the
last measurement
indefinitely, or
until reset by the RESET pushbutton or an
external
signal.
Thedisplay
timecircuit is locked to the
1
ms
through
10s
MEASUREMENT INTERVAL pushbuttonsso that the
total
display time
is
the sum
of the DISPLAY TIME control set
ting and the
measurement
interval
selected.
When
used with manual gate operation, the DISPLAY
TIME control
determines
when to totalize the counts made
during
separate gate intervals (for further information,
see
Totalize under Measurement
Modes).
2-7
Содержание 7D14
Страница 4: ...7D14 ...
Страница 11: ...Operating Instructions 7D14 Fig 2 1 7D14 front panel controls and connectors 2 2 ...
Страница 24: ...W Fig 3 3 Channel A Signal Conditioning circuit detailed block diagram Circuit Description 7D14 ...
Страница 33: ... 3 13 Fig 3 11 Logic diagram for Zero Cancel Logic stage Circuit Description 7D14 ...
Страница 38: ...3 18 Fig 3 16 Time Base and Control circuit detailed block diagram Circuit Description 7D14 ...
Страница 44: ...NOTES ...
Страница 46: ...NJ Fig 4 1 Electrode configuration for semiconductors in this instrument I ...
Страница 68: ...NOTES ...
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Страница 98: ...GRS 0371 BLOCK DIAGRAM ...
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Страница 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 ...
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Страница 110: ...A2 Logic Circuit Board Assembly jQ798i 798 jc743 CR744t uni R724 R742 JL744S FrR796 ...
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Страница 114: ...P 0 A2 LOGIC BOARD ...
Страница 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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Страница 130: ...4 7D14 DIGITAL COUNTER ...