I have been wondering why I get so much noise on the phase measurement for low frequencys. I looked into this and as i see it, the Tsunami does no averaging inside the controller and so it can not properly measure the phase of signals which are in the range of Tau=R8*C2 or slower, right?
If I need correct phase measurements at low frequencies and can easily sacrifice fast update rates, wouldn't it be a good idea to replace C2 by someting like RS Part.-No. 788-2893 (Multilayer chip capacitor, X5R, 10μF ±10% / 10 V dc, SMD 0603)?
You're right that this is a tradeoff: a larger capacitor gives more stable results at low frequencies, at the cost of lower update rate. If that's a tradeoff you want then yes, that's absolutely a good solution. Let us know how you get on with it!
I piggibacked some standard 10u Electrolytic Cap and yes, works much better at low frequencies!
Images below are what you get when you sweep an RC Highpass with 47nF C and 1000k R. Images are: TINA-TI simulation, Tsunami sweep with standard C and sweep with 10uF Piggiback.
I think, the Notch at the beginning means that the Tsunami is no €100k Testequipment when it comes to dynamics ... at -15dB, it has trouble measuring the Phase correctly, When I measure a Loop cable, the Phase is flat. I would say that is perfectly what you can expect and can be fixed with an amplifier and a little bit of brainpower.
"New users can't post images", you have to add a "h" to the url