Chapter 4
Exercises
Preparation
For these exercises you will need a ‘9X’ counter, a function
generator and two BNC cables of approximately equal length. Set
up the generator according to the following table, and connect
the main output of the generator to input A of the counter.
Basic Startup
Since the counter will remember its previous setting in nonvolatile
memory, it is recommended that you recall the factory default
setting before you begin.
To do so, first key in the following sequence:
USER OPT -
Save/Recall
-
-
Recall Setup
-
Default. Then press the AUTOSET key
twice within two seconds. The preselected measurement
function will be Frequency, and the trigger levels will be
automatically adjusted in relation to the applied signal.
If a signal with a frequency of 20 Hz or higher and an amplitude
large enough to trigger the counter is connected to input A, its
frequency will now be displayed.
High-Resolution Frequency
Measurement
Note the high resolution of the primary readout. Twelve digits
are displayed in a measuring time of 1 s. Don’t worry about the
trigger settings, the AUTO trigger will take care of any input
signal above 20 Hz. This frequency limit can, if so desired, be
changed down to 1 Hz or up to 100 kHz with a tradeoff between
frequency and measurement speed. If the generator has been
set up properly, you will now read the frequency (1 MHz) on the
display.
Built-In Math Processing
With the built-in math functions, you can make post-processing
operations like scaling and offsetting an easy benchtop task
without having to hook up a computer to the instrument. You
can, for example, display any deviation from the desired value
instead of directly showing the result of the measurement itself.
This is known as offsetting.
In the following, the direct, unscaled result of the counter’s
measurement process will be referred to as ‘X’.
To set up the counter to display any deviation from 1 MHz, press
the MATH/LIM key and select Math. The display will show that
Math is still Off. Press the soft key below the Math Off indicator
to enter the Formula Select menu. Use the cursor keys to mark
the formula K*X/M + L and confirm by pressing the EXIT/OK key.
Now enter the numerical values for the constants K, L and M.
The default values are: K=1, L=0 and M=1. In this case only L has
to be altered to -1*106 in order to get the job done.
Open the value input menu for L by pressing the soft key below
the menu heading marked L on the display. Press 1 followed by ±,
EE (short for Enter Exponent) and 6. Confirm and exit by pressing
EXIT/OK. Press EXIT/OK repeatedly until the display is showing
the measurement result, now modified to reflect any deviation
from 1 MHz.
Change the generator frequency upward and downward just a
little, and watch the counter’s display.
High-Speed Measurements
The benefits of high speed measurements for benchtop use
become obvious when you use statistics. For instance, the ‘9X’
can make 1000 7-digit measurements and present the standard
deviation (jitter) in less than one second.
Recall the default setting and press AUTOSET twice within two
seconds before tweaking the controls to reach the optimum
measurement speed for your application. See the following two
paragraphs.
Under the INPUT Menus:
Auto trigger level settings in this model is so fast that you will
normally not notice any difference in speed if auto is on or off.
However, if you use statistics to make hundreds or thousands
of measurements, the fractions of a second it takes to calculate
trigger levels before each measurement add up to a considerable
time over the total sequence.
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