Frequency sweep input output

Hi
Using Labview 7.1 and PCI 6071 DAQmx card i want to design a frequency sweep application. I mean that i need my analogue output channel to give a sine wave with incremental frequency of 100 Hz step, starting from 10000 Hz untli 100000 Hz (10000 Hz, 10100 Hz...100000 Hz). This wave is applied on a kind of a transformer, and each time the frequency changes, i need an input channel to acquire another also sinus wave coming from this transformer and measure its amplitude, in order to examine its frequency response. So, i came up with the attached vi.
The problem is, that when "sweeping" takes place ,i get amplitude values between 2 and 6 or even 7 volts something that can't be happening. I know that the amplitude values i should get are around 2 volts (+/- 500 mV maximum).
I think, that the problem should be in some kind of "non-synchronization" of the input-output channels when the vi enters the loop to start changing the frequency.
Just to be more clear, i need my vi to do these steps in order:1. constantly output the 10000 Hz wave 2. acquire the input wave 3. measure its amplitude 4.transform the frequency into 10100 Hz 5. acquire the input wave 6. measure amplitude etc...
The odd thing is that when i physically connected the output channel with the input one to see if the frequency sweep is done, it worked fine. I mean that i did get in the input channel almost exactly the signal i generated.
Thanks in advance, and i hope i was not tiringly analytical..
Attachments:
sweep3.vi ‏140 KB

Hi
Please take a glance at the two attached vi's.
The first is the one i use in order to generate a steady frequency sinus wave,feed it to my transformer and acquire the also sinus output of the transformer through my input channel. Using two channels of an external oscilloscope i check and notice that for many frequency values, both sinus waves are steady and noiseless, with the expected amplitude voltages.
Now, using the second vi, in order to "sweep" the wave and check my transformers amplitude response, then these impossible amplitude "up's and down's" again came up.Again by looking at the oscilloscope's screen i can see the noisy waves tha "confuse" and the oscilloscope and my input channel, and so result in wrong amplitudes.
Based on the above, i have to assume, that the problem lies in the sweep mechanism design i use. Also, after trying several different ways to sweep, i came to the conclusion, that the problem comes up whenever i use the second Basic Function Generator.vi inside the loop. Could it be that it needs triggering again?
I'd really use some help, or maybe even ideas for different design approaches for the frequency sweep.
Thanks in advance
Attachments:
Multi-Function-Synch AI-AO3.vi ‏164 KB
sweep4.vi ‏142 KB

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Message Edited by SFK on 08-12-2009 04:12 PM
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