Question about measurement results of "Getting Started"

QA40x
1 
Good evening everyone,
I reproduce the measurement from "Getting Started"
https://github.com/QuantAsylum/QA40x/wiki/Getting-Started

My results of THD and THD+N are very close to each other,
the other values ​​are very similar to the given example.

Here the example from "Getting Started"

Where does this come from?

157280139-a8a26bad-df22-48a7-917b-7b590be03a4c
157280139-a8a26bad-df22-48a7-917b-7b590be03a4c1308×1005 65.7 KB

selftest
selftest800×1019 24.9 KB
2

Where does what come from? Not sure what your point is.

3

Hi @Diskus, do you mean why is your THDN so high? It looks like you have a lot of noise below 60 Hz or so. What is your FFT size? Do you have shorting block on the unused INPUT? Thanks!

4

Also with maximum attenuation there’s the attenuator’s Johnson noise.

1 Like