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Making Measurements
Measurement Accuracy and Speed
Accuracy
The value of –12 dBm lies in the lower range of the Agilent E- series E9300
power sensor. In autoranging mode ("AUTO") the Agilent EPM series power
meter determines the average power level is below –10 dBm and selects the
low power path. However, the peak amplitude of –6 dBm is beyond the
specified, square law response range of the low power path diodes.The high
power path (–10 dBm to +20 dBm) should be used to ensure a more
accurate measurement of this signal. However, range holding in "UPPER"
(the high power path), for a more accurate measurement, results in
considerably more filtering.
Speed and Averaging
The same signal also requires that consideration is given to measurement
speed. As shown above, in autoranging mode the Agilent EPM series power
meter selects the low power path in the Agilent E- series E9300 power
sensor. With auto- averaging also configured, minimal filtering is applied.
Values of 1 to 4 for average power levels above –20 dBm are used in the low
power path. (Refer to "Auto- averaging Settings" on page 23.)
If the range is held in "UPPER" for more accuracy, the measurement is
slower. More filtering is applied due to the increase in noise susceptibility at
the less sensitive area of the high power path. Values of 1 to 128 for average
power levels less than –10 dBm are used. (Again, refer to "Auto- averaging
Settings" on page 23.) Manually lowering the filter settings speeds up the
measurement but can result in an unwanted level of jitter.
Summary
Attention must be paid to signals whose average power levels are in the low
power path range whilst their peaks are in the high power path range. You
can achieve best accuracy by selecting the high power path or best speed by
selecting the low power path.
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