Making Measurements 5
6000 Series Oscilloscope User’s Guide 237
Counter
The 6000 Series oscilloscopes have an integrated hardware
frequency counter which counts the number of cycles that
occur within a period of time (known as the gate time) to
measure the frequency of a signal.
The gate time for the Counter measurement is automatically
adjusted to be 100 ms or twice the current time window,
whichever is longer, up to 1 second.
The Counter can measure frequencies up to the bandwidth
of the oscilloscope. The minimum frequency supported is
1/(2 X gate time).
The measured frequency is normally displayed in 5 digits,
but can be displayed in 8 digits when an external 10 MHz
frequency reference is provided at the 10 MHz REF rear
panel BNC and the gate time is 1 second (50 ms/div sweep
speed or greater). See (“To supply a sample clock to the
oscilloscope” on page 324.)
The hardware counter uses the trigger comparator output.
Therefore, the counted channel’s trigger level (or threshold
for digital channels) must be set correctly. The Y cursor
shows the threshold level used in the measurement.
Any channel except Math can be selected as the source.
Only one Counter measurement can be displayed at a 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.
Digital channel time measurements
Automatic time measurements Delay, Fall Time, Phase, Rise Time, X at Max, and
X at Min, and are not valid for digital channels on mixed-signal oscilloscopes.
Duty cycle =
+ Width
Period
-------------------
X 100
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