User`s guide

Making Measurements 4
5000 Series Oscilloscope User’s Guide 187
Counter
The InfiniiVision 5000 Series oscilloscopes have an integrated
5-digit 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 hardware counter uses the trigger comparator output.
Therefore, the counted channel’s trigger level 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.
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.
Duty cycle =
+ Width
Period
-------------------
X 100