Keysight n1921a Operating And Service Manual page 41

Figure 3-2
Although the rise time specification is ≤13 ns, this does not mean that the
combination of P-Series power meter and power sensor can accurately measure a
signal with a known rise time of 13 ns. The measured rise time is the root sum of the
squares (RSS) of the signal-under-test rise time and the system rise time (13 ns):
Measured rise time
The % error is:
Keysight N1921A and N1922A Operating and Service Guide
Measured rise time percentage error versus signal-under-test
rise time
= SignalUnderTestRiseTime
( (
MeasuredRiseTime SignalUnderTestRiseTime
(
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
%Error =
–
SignalUnderTestRiseTime
(
Theory of Operation
2
+ SystemRiseTime
) (
)
)
3
2
) )
×
100
41