58542 VXIbus Universal Power Meter
2-36 Publication 21555, Rev. E, September 2002
2.5.20 Averaging
■ SENSe:AVERage
Averaging is applied during normal operating mode. In the normal mode, Avg
n
results in
n
x 192
samples taken. In the Swift or Burst modes, Avg
n
results in 2
n
samples taken. Auto averaging takes 4
samples all the time. For auto averaging in the normal mode, the averaging number is level dependent
with very low averaging at +20 dBm, and many samples taken at very low levels.
SENSe:Average
Syntax:
SENSe<sensor 1 or 2>:AVERage:COUNtspace<1,2,4,8,16,32,64,128,256,or 512>
Example:
OUTPUT @PWR_MTR;SENS1:AVER:COUN 16 ! SETS SENSOR 1 AVERAGE NUMBER TO 16
Description:
This command averages successive sensor readings in a digital averaging filter. As the
measured signal level approaches the noise floor of the power sensor, measurement data
values begin to fluctuate. To measure very low signal levels (within a few dB of the sensor
noise floor), set a large value for averaging such as 128, 256, or 512. Be sure to zero the
sensor, CALibration:ZERO, prior to critical measurements.
Syntax:
SENSe<sensor 1 or 2>:AVERage:COUNt:AUTOspace<ON | OFF>
Example:
OUTPUT @PWR_MTR;SENS2:AVER:COUN:AUTO ON ! SELECTS SENSOR 2 AUTO-AVERAGING MODE
Description:
Auto-Averaging optimizes the measurement averaging value for reading stability and update
rate when the measurement data is being repeatedly updated. At high power levels
(measured), minimum averaging is applied to optimize measurement speed. As the power
level drops, additional averaging is applied to steady the measured data reading.
Syntax:
SENSe<sensor 1 or 2>:AVERage:TCONtrolspace<data acquisition averaging method,
MOVing or REPeat>
Example:
OUTPUT @PWR_MTR;SENS1:AVER:TCON REP ! SETS SENSOR 1 TO ACQUIRE FRESH
! MEASUREMENT DATA BEFORE AVERAGING
Description:
The SENSe:AVERage:TCONtrol commands are instrument level commands that control the
internal measurement data averaging of the power meter. Two modes are selectable, MOVing
and REPeat.
The MOVing control applies the current measurement to the previously measured data. That
is, even if the averaging number is 16, a measurement data point every time a sample is
taken will occur, not just after every 16 samples. There is some limited built in level sensing
capability. For example, when Auto-Averaging is used and the power is suddenly changed
from a low value to a high, MOVing averaging throws out the very low level previous data as
the gain range changes and begins averaging fresh data. Thus, wide abrupt changes in
power level are not masked by the MOVing averaging. The 58542 can fully range in about
4 ms. MOVing averaging is similar to TR1 mode in typical benchtop power meters.
REPeat averaging performs full averaging every time the 58542 is triggering. Unless the
averaging number is set to 1, REPeat is slower than MOVing averaging. REPeat control is
similar to TR2 mode in typical benchtop power meters. Fresh data is measured and averaged
with each complete measurement cycle.
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