start stop aquisition from measuring signal

[gfds]

I generate a sinusoidal signal of frequency in the range 0-30kHz supplying piezotransducer. For pictures of the characteristisc I measure current and tension. My issue is with saving an automatic pass. Currently, the program I use the recorging time is done in record time, set time. Build by me generator generaites repetitive signal, in respons I would like to get only one recorded tension and current signals. For example start at 0 Hz and stop at maz Hz or something with amplitude. Just need to analyze, investigate a signal which to my mind nothing comes. Could someone help me solved the problem start stop recording. In which way I could do that?

I am user of usb 6251 card ni and Labview 8.5. Here I must point out that the generation and recording takes place quickly.

Bestregards,

Marek 

[YannC]

Hi gfds,

I'm afraid but I don't understand what you want to do.

Can you try to explain what you want to do in more detail?

Regards

[gfds]

Hey YannC,

Thank You that You are all the time with responded. 

I would like aquisie just one period, whith is started at minimum frequency and stoped at maximum frequency. In one programe I have generator and aquisition and there are separated. For generated signal I have used Assistent Daq, for aquisition Daqmx bloks as an atachement vi in ferst post. 

Bestregards,

Marek

[gfds]

My problem is that I can not set up fft bloks for watching frequency of this signal. After than make a condition loop whith working will be depondant on frequency for controling start and stop.

[YannC]

Hi,

Can you tell me what is connected to ai1 and ai2?

You have some examples available on LabVIEW, open the research tool for example(aide»Recherche d'exemples)and search  "sweep"(see picture).

In my case, the five last examples for DAQmx card is rather similar to what you want .

Can you try this example?

Regards,

[gfds]

In input ai1 is connected tension and ai2 current par current transformator with parallel resistance.  Generator I have connected to ao0.For me your atached exemples are unvisible. Could you insert them in this post? I've atached view of connection and view of my available exemples.

Thank you for help.

Marek