Tabor Electronics 5064, User Manual

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3
Using the Instrument
Pulse Design Limitations
3-61
Trigger Level
The trigger level parameter defines the vertical cross point where
the signal will trigger a measurement. Trigger level range is from -5
V to +5 V and the default threshold level is set to 1.6 V, which is
very convenient for TTL level signals. To change the default level,
select the Trigger Level menu and modify the level using direct
keyboard entry. Press Enter to lock in the new value.
Trigger Slope
The Trigger Slope defines on which transition the counter input will
trigger. There are two options: Positive and Negative. The default
option is positive, which means that the counter will trigger on
positive transitions at the counter input. The trigger slope parameter
is also used for defining the measured portion of a pulse. When in
pulse width measurements, the counter will measure the width
when transitioning from low level to high level and when the
negative slope is selected, the counter will measure the high to low
level transitions.
Reset/Arm
The Rest/Arm button has two functions: Reset removes the last
reading from the display and zeroes the reading. At the same time,
the counter is armed for the next measurement. Use this button to
clear the display reading when the display time is set to hold.
Counter/Timer
Limitations Keeping in mind that the counter/timer is a by-product of the AWG,
one should understand there are limitations to what this product can
do. Summary of the counter/timer limitations is given below.
1. Measurement speed
What is expected from a full-featured counter/timer is measurement
speed. The rate of which the counter performs its measurements
depends on the display mode setting. The Normal setting is
normally used for bench reading, where the user expects to see the
result after each measurement. The display time is roughly 300 ms
allowing enough time to see the result after each gate time cycle. In
this case, the maximum rate is 3 measurements in one second
when using low period gate times. The Hold display mode allows
one reading at a time. The reading starts when the input senses a
valid trigger signal and ends after the gate has closed. Processing
time for the reading and the display is roughly 100 ms and
therefore, in this mode, the counter can take 10 readings maximum
in one second. Regardless of the display mode, the readings are
also available for collection from a remote interface.
2. Gate time period must be higher than the signal period
In Fact, this limitation is true for every counter. The gate must open
for an interval that allows enough transitions to pass through the
counter gate. If the gate time is too short to measure a signal, the
gate will open but no results can be obtained and displayed.