how to choose sample fréquency

[123M]

I have a chart of acquisition for Ni pci-6281M SERIE , my question is how to program  low-pass filter and how to choose the frequency of sampling in mode continuous sampel,  and cut's buffer in éxecution. I usethesoftwareLabVIEWsignalexpress 

[Andy-C]

Hi 123M,

You may receive more guidance if you can provide some more detail of your application. What type of signal are you bringing into the 6281 card? Is this from a sensor? If so, what make/model/type of sensor?

As for adding filters in Signal Express, you should read the Signal Express Help file here.

Andy C.

Applications Engineering 

National Instruments 

[123M]

Salut Andy-C et je vous remercier beaucoup.  J’ai un capteur de contrôle non destructif  à « courent de Foucault » qui une bobine qui a les caractéristiques suivantes :

nombre de spires =170

le rayon intérieur =2.35mm

le rayon extérieur =4.5mm

hauteur =2.2mm

Je veux acquérir avec la carte pci-6281 une tension et un courant pour un signal d’alimentation :

V=2V valeur efficace

f=100khz fréquence

 Ma question est comment choisir le paramètres de cadencement (fréquence d’échantillonnage et la taille d’échantillon à lire) et comment mesurer le courant, logiciel utilisé LabVIEW signalexpress.  

[123M]

translate in english

Hi Andy-C and I thank you very much. I have a sensor for non-destructive control "eddy current" that a coil that has the following characteristics:
170 = number of turns
the inner radius = 2.35mm
the outer radius = 4.5mm
height = 2.2mm
I want to acquire with the pci-6281 voltage and current for a powersignal:
V = 2V rms
f = 100khz frequency
  My question is how to choose the timing parameters (sampling rate and sample size to read) and how to measure the current. software used LabVIEW signalexpress .

[Henrik_Volkers]

For 100kHz use 500kSPS or the max samplerate

Sample length?....

Well, it depends a lot on what you want to measure. 100kHz sine: amplitude and phase?  (
Distortion? Your max samplerate is 625kHz , hardly enougth to capture the 2. and 3. harmonic (300kHz migth be already cut by the aliasing filter)

How fast do you need the result? If you capture a long time your cycle rate is low.

I haven't done eddy current measurements, so my first try would be: capture 20 periodes, use single tone detection and record amplitude, phase* and the RMS of the residual.

*) that would involve that you can sync to your exitation signal