The measuring speed can be increased substantially if you set
the trigger levels manually once, before a lengthy measurement
sequence starts.
Press INPUT A and choose MAN for the MAN/AUTO setting.
Now press Trig to open the trigger level value input menu. Enter
a level of +0.5 V. Confirm the selection by pressing EXIT/OK
twice.
Under the SETTINGS Menu:
By making the measuring time for each sample as short as
possible you can also increase the overall measuring speed.
Remember, however, that there is always a tradeoff between
measuring time and resolution.
Press SETTINGS and then MeasTime. Use the DOWN arrow
key to set the measuring time to the minimum value. Confirm by
pressing EXIT/OK twice.
Now the counter is taking measurements at a very high speed.
Toggle the STAT/PLOT key to see the statistical measures and
the graphical presentation of the result.
The measuring speed can be increased even more, if you take
advantage of the features that are available over the GPIB.
These include commands for turning off the display update,
etc. In this way you can reach speeds up to 2000 transferred
measurements/s, each individually triggered. If you save the
results to the internal memory of the instrument for later
transfer, you can even attain an impressive speed of 250,000
measurements/s.
Time Measurements
So far we have only been using the frequency function. Now we
will use some others.
To measure the period of the signal, simply press the key
MEAS FUNC followed by PERIOD. Select SINGLE or AVERAGE
depending on the desired resolution and measuring speed. Finish
by selecting the input channel.
To measure pulse width, use the keys MEAS FUNC and PULSE
followed by POS or NEG depending on whether you want to
measure the positive or the negative pulse width. Finish by
selecting the input channel.
Jitter Measurements (Statistics)
You can make statistical measurements, such as pulse width
jitter, directly via the front panel of the counter.
Make sure the counter is measuring positive pulse width on input
A. To turn on statistics, press the STAT/PLOT key. Change the
display mode by toggling the same key. Return to the numerical
mode and watch the results. The display gives you a survey of
several statistical measures. See also page 3-4. The rms jitter
is equivalent to the standard deviation of 100 measurements,
where 100 is the default value for the sample size.
If you want to change the default values for sample size, bin size
or pacing time, then you can press the SETTINGS menu key and
after that the STAT soft key.
Other Single-Channel
Measurements
The counter/timer can help you characterize signals even further.
Recall the default settings and press AUTOSET twice.
Duty Cycle
Use the MEAS FUNC key to select Duty and then Positive
A (for positive-pulse duty cycle measurement on channel A).
Change the frequency of the generator to 10 kHz. Then vary the
symmetry (duty cycle) of the square wave on your generator. The
counter’s display will directly show the duty cycle as a number
between 0 and 1. There is no need to manually calculate duty
cycle by dividing pulse width by period.
The duty cycle (D) is defined as: D=W / T
D = 0.5 for a square wave.
Rise Time
Use the MEAS FUNC key to select Time, Rise Time and A (for
channel A). Press INPUT A and make sure the following settings
are active:
•
Coupling DC
•
Impedance 50 Q.
•
Attenuation 1x
Notice the rise time for a square wave, which is measured totally
automatically.
Now change the generator output to a triangular waveform. See
next figure.
Vary the rise time and notice the difference on the display.
12
