NI 4551 measurable frequencies under swept sine mode

[xcomas]

What is the highest measurable frequency for the NI 4551 under the swept sine mode?

[Minh T.]

Good afternoon xcomas,

The 4551 samples at a maximum rate of 204.8 kS/s.  So the maximum frequency of a signal that it can measure would be theorectically half this (following Nyquist) at 102.4 kHz. 

I am not certain what you mean by swept sine mode, the 4551 is a Dynamic Signal Acquisiton card, it acquires signals, you can certainly choose to send a swept sine to it, in which case the sweep can go as high at 102.4 kHz.

Have a look at the NI 4551/4552 User Manual, it should have all the specs you're looking for:

http://digital.ni.com/manuals.nsf/websearch/6A32358C53BB15F086256660007392DC

Please let me know if this answers your question and if you have any further questions.

Minh Tran

Applications Engineering

National Instruments

[Jack_A.]

Minh was talking about using NI-DAQ mode of the 4551 while I believe you are referring to using the swept sine mode in the DSP which you program using NI-DSA.  A good general resource for some of these types of questions is in the NI-DSA User Manual.

Here's an excerpt from it:

"The update rate of your output is determined by the scan rate set for the inputs. If you change the input rate, the update rate is the same as the scan rate if the scan rate is less or equal than 51.2 kHz; one-half the scan rate if the input scan rate is between 51.2 kHz and 102.4 kHz; and one-fourth of the scan rate if it is between 102.4 kHz and 204.8 kHz."

This means that the highest update rate used on the 4551 is 51.2kS/s  which means that you can generate frequencies just above 20kHz

Hope this helps,

Jack

[xcomas]

Dear Jack,

thanks a lot for your message. You're absolutely right with your assumptions. That is a big help. I was trying to figure out if there was any way to get into a high frequency range (MHz scale) with my instrument. I've been using it before to take low frequency measurements on soil samples (to determine electrical behaviour and properties). I guess I would need something different to measure on the MHz scale (e.g. impedance analyzer)...

thanks again for your reply...

Xavier

[xcomas]

thanks a lot Minh,

see reply to Jack for further explanation on what I was trying to do, but thanks again for your time and response...

Xavier