Averaging Measurements; To Use Measurement Averaging; Example Of Using Measurement Averaging - HP 8920A User Manual

Averaging Measurements

To Use Measurement Averaging

The AVG (average) function allows you to display the average value of a number
of measurements. You enter the number of measurement samples used to
calculate and display the measurement average. This dampens the effects of
rapidly changing measurements, providing a more usable measurement display.
1. Position the cursor in front of the measurement's unit-of-measure.
2. Press and release the SHIFT key, then the INCR ×10 key to access the AVG function.
The default number of average samples is displayed below the measurement.
• Enter the desired number of measurement samples to be used for calculating the av-
erage, or
• Press ON/OFF to use the currently-displayed number of samples.
3. To turn averaging off, position the cursor in front of the unit-of-measure and press and
release the SHIFT key, then the INCR ×10 key to access the AVG function, then press
the ON/OFF key.
When the averaging function is first enabled, a numeric average is calculated and
displayed each time a measurement is made. This continues until the specified
number of samples is reached. From that point on, the averaging function
performs an exponential filtering operation that mimics an RC filter.
Because of the exponential response, any large measurement changes result in a
displayed value that ramps up or down to the actual measured value.
Pressing MEAS RESET clears the measurement history for all measurements and
starts the averaging process over.
For more information on the theory of this filtering technique, refer to the April
1986 issue of the HP Journal, page 24.

Example of Using Measurement Averaging

This example enables the SINAD measurement to be averaged using 25 samples.
1. Press PRESET and wait for the instrument to display the RX TEST screen.
2. Position the cursor in front of the unit-of-measure for the SINAD measurement (default
is dB).
3. Press and release the SHIFT key, then the INCR ×10 key to access the AVG function,
enter 2 5, then press the ENTER key. Avg appears below the displayed measurement
value to indicate that averaging is being used.
Chapter 3, Operating Overview
Averaging Measurements
69