Appendix 
622 
The crest factor of the user-defined distribution is:  
2
1
0
minmax
1
2
i
N
i
Sample
N
SampleSample
cf
 
 
Where N is either 16384 or 524288 (for 81150A).  
 
 
 
7.5.1  Limitations of User-defined Noise Distributions 
 
 
 
Due to bandwidth limitations of the output amplifier, the measured 
histogram does not perfectly match the defined distribution. 
The difference between the calculated crest factor of the user defined 
distribution and the measured histogram depends on the amplifier path 
being used and on the distribution itself.  
 
 
Example of user 
defined distribution 
defined by Ramp 
waveform 
The following example shows a user defined distribution that is defined by a 
ramp waveform. This should lead to an equal distribution of all voltage levels 
in the output signal. Due to the bandwidth limitations and asynchronous 
sampling of the oscilloscope, the measured histogram is not rectangular as 
expected.