Agilent Technologies 54621A User Manual page 212

Making Measurements
Making time measurements automatically
Measurement definitions
Measurement thresholds for time measurements
The default lower, middle, and upper measurement thresholds are 10%, 50%, and
100% between Top and Base values. See the previous topic "Setting measurement
thresholds" for other percentage threshold and absolute value threshold settings.
Counter
The Counter measurement counts trigger level crossings at the selected trigger
slope and displays the results in Hz. The gate time for the measurement is
automatically adjusted to be 100 ms or twice the current time window, which
ever is longer, up to 1 second. Any channel except Math may be selected for the
source. Only one Counter measurement may be displayed at a time.
The Y cursor shows the edge threshold level used in the measurement.
The Counter measurement can measure frequencies up to 125 MHz. The
minimum frequency supported is 1/(2 X gate time).
Duty Cycle
The duty cycle of a repetitive pulse train is the ratio of the positive pulse width
to the period, expressed as a percentage. The X cursors show the time period
being measured. The Y cursor shows the middle threshold point.
+ Width
------------------- - X 100
Duty cycle =
Period
Frequency
Frequency is defined as 1/Period. Period is defined as the time between the
middle threshold crossings of two consecutive, like-polarity edges. A middle
threshold crossing must also travel through the lower and upper threshold levels
which eliminates runt pulses. The X cursors show what portion of the waveform
is being measured. The Y cursor shows the middle threshold point.
Period
Period is the time period of the complete waveform cycle. The time is measured
between the middle threshold points of two consecutive, like-polarity edges. A
middle threshold crossing must also travel through the lower and upper
threshold levels which eliminates runt pulses. The X cursors show what portion
of the waveform is being measured. The Y cursor shows the middle threshold
point.
5-42