Specifications
Power Meter Supplemental Characteristics
HP EPM-441A/442A Service Guide 1-7
Zero Drift of Sensors
Power sensor dependent (refer to Table 1-3).
Measurement Noise
Power sensor dependent (refer to Table 1-2 and Table 1-3).
Averaging effects on measurement noise. Averaging over 1 to 1024
readings is available for reducing noise. Table 1-3 provides the
measurement noise for a particular power sensor with the number of
averages set to 16 for normal mode and 32 for x2 mode. Use the “Noise
Multiplier” for the appropriate mode (normal or x2) and number of
averages to determine the total measurement noise value.
For example, for an HP 8481D power sensor in normal mode with the
number of averages set to 4, the measurement noise is equal to:
(<45 pW x 2.75) = <124 pW
Table 1-2: Noise Multiplier
Number of
Averages
1 2 4 8 16 32 64 128 256 512 1024
Noise Multiplier
(Normal Mode)
5.5 3.89 2.75 1.94 1.0 0.85 0.61 0.49 0.34 0.24 0.17
Noise Multiplier
(x2 mode)
6.5 4.6 3.25 2.3 1.18 1.0 0.72 0.57 0.41 0.29 0.2
4402serv.book Page 7 Monday, March 11, 2002 11:34 AM
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