1050
Meas Setup
Log-Pwr Avg (Video)
Selects the logarithmic (decibel) scale for all filtering and averaging processes. This scale is sometimes
called “Video” because it is the most common display and analysis scale for the video signal within the
test set. This scale is excellent for finding CW signals near noise, but its response to noise-like signals is
2.506 dB lower than the average power of those noise signals. This is compensated for in the Marker
Noise function.
The equation for trace averaging on the log-pwr scale is shown below, where K is the number of
averages accumulated. (In continuous sweep mode, once K has reached the Average/Hold Number, K
stays at that value, providing a continuous running average.)
New avg = ((K–1)Old avg + New data)/K
Assumes all values in decibel scale.
Pwr Avg (RMS)
In this average type, all filtering and averaging processes work on the power (the square of the
magnitude) of the signal, instead of its log or envelope voltage. This scale is best for measuring the true
time average power of complex signals. This scale is sometimes called RMS because the resulting
voltage is proportional to the square root of the mean of the square of the voltage.
In the equation for averaging on this scale (below), K is the number of averages accumulated. (In
continuous sweep mode, once K has reached the Average/Hold Number, K stays at that value, providing
Couplings Here are the auto-select rules for Average Type:
Auto selects Voltag e Averag ing if the Detector for any active trace is EMI
Average or QPD or RMS Average; otherwise it selects Power (RMS)
Averaging if a Marker Function (Marker Noise, Band/Intvl Power) is on, or
Detector is set to Man and Average; otherwise if Amplitude, Scale Type is
set to Lin it selects Voltage Averaging; otherwise, if the EMC Standard is set
to CISPR, it selects Voltage; otherwise Auto selects Log-Power Average.
Note that these rules are only applied to active traces. Traces which are not
updating do not impact the auto-selection of Average Type.
State Saved Saved in Instrument State
Readback The type auto-selected is displayed in the readback line on the Average Type
key
Initial S/W Revision Prior to A.02.00
Key Path Meas setup, Average Type
Example AVER:TYPE LOG
Notes See ““Average Type” on page 1048”
Couplings See ““Auto” on page 1049”
Readback Log-Pwr (Video)
Initial S/W Revision Prior to A.02.00