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Model 5328A
Operation
3-80.
External Frequency Standard Input
3-81.
The rear panel external frequency standard (OSC INT EXT) input is useful for locking the
counter to a high stability external frequency standard.
This external standard must be in the
range of 30 kHz to 10 MHz with an amplitude of >1V rms into 1 kQ (maximum input of 5V
peak-to-peak).
If the frequency input is not 10 MHz, the counter operates with frequency
measurements multiplied by the factor 10 MHz/fext and time measurements multiplied by the
factor fext/10 MHz. For example, in a frequency measurement, a1 MHz external standard would
give a 100 second measurement time for the RESOLUTION switch in the .1Hz positon and would
display a 100 kHz input as 1000 kHz whereas, ina period measurement (with RESOLUTION set for
maximum) a 100 kHz input (10 usec period) would be displayed as 1 usec. The measurementtime,
however would be unaffected.
3-82.
For the Option 040 only, the external frequency standard must be 10 MHz for PERIOD
AVG, T.l. AVG AB, PERIOD (N=1), and T.!. A>B (N=1). Otherwise, phase lock will not be
achieved and the time base signal will bear no relationship to the frequency of the external
frequency standard.
3-83.
Marker Outputs
3-84.
The marker outputs for the standard and for the Option 040 universal module are
described in the following paragraphs.
3-85.
MARKER OUTPUTS (STANDARD).
Two marker output connectors are mounted on the
front panel of the universal module. These outputs represent the inverted channel A and channel
B Schmitt triggers. The outputs provide 0 to -100 mV levels into 502 delayed by less than 20 ns.
These outputs are very useful for oscilloscope monitoring. Time interval measurement set-ups
are simplified if the time interval of interest and the marker outputs can be simultaneously
displayed on oscilloscope traces.
Frequency measurements on noisy signals can be made with
more confidence since the markers can indicate the presence of noise triggering. These outputs
are protected from inadvertently applied voltage to +5V dc.
3-86.
MARKER OUTPUTS (OPTION 040). The Option 040 universal module has a channel A
marker output like the standard universal modules. The other marker output is aT.1. A>B marker
which is high during the time interval measured by the counter, delayed by less than 20 ns. The
levels are 0 to -100 mV into 50 for the A marker; 0 to -50 mV for the T1, A—B marker.
These
markers are extremely helpful in time interval measurement set ups. The marker outputs do not
show the effect of the Option 040's delay control.
3-87.
Gate Out
3-88.
This rear panel output supplies a TTL level which is high when the counter's main gate is
open and low when it is closed. Monitoring the GATE OUT onan oscilloscope can provide this
information
for applications where the markers do not give the desired information. For
example, when using the delay of the Option 040 and on armed measurements (even though the
channel is triggering, the main gate may not be open if the counter hasn't been armed).
3-89.
Time Base Out
3-90.
The TB OUT connector on the rear panel supplies a TTL level output when the FUNCTION
switch is in START CLOCK or START A position (see Figure 3-8). In START CLOCK, the internal
oscillator 10 MHz is divided by N where N is selected by the RESOLUTION switch. When in START
A function, the input at channel A, divided by N (for N>1), is available at the time base out rear
panel connector.
3-91.
External Frequency Standard
3-25
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