I observe unstable rms and peak-to-peak values between measurements using 5411 and 5620 (both located in a pxi) when the frequency is a multiple of two.
With this array of frequencies is: 2,3,4,5,6,7,8,9,10MHz the Vrms and Vp2p values that I read everytime for 2, 4, 8... are unstable. The higher the frequency, the higher the variarions. I manage to workaround the problem by not using frequencies multiple of 2, like e.g.: 1.9, 2.8, 3.7,4.6, 5.5, 6.4 7.3, 8.2, 9.1, 10MHz but I still would like to understand why. Does this have anything to do with the internal clock signal, harmonic distorsion maybe?