Fgen_Sweep_Generator reading frequency

[steve h]

Using a ni5402 signal generator and the niFgen_Sweep_Generator_Example.vi.

How can I read/display the actual frequency that is being outputed whilst the signal generator is ramping?

[alpha1]

Hi Steve,

Sorry for the long delay in anyone getting back to your post. I've looked into the problem and attempted to find a way to read back the data on the signal generator, unfortunately without any luck. I think the easiest way to read & display the actual frequency would actually be by physically reading the output of the signal generator back into LabVIEW via a signal acquisition card.

Sorry for not being able to find an alternative solution to the problem.

[steve h]

It seems this sig generator is not very user friendly in this matter.

I tried a aquiring the frequency via a NI 4070 DMM but found that that was too slow as it took over a second to measure the frequency and as I was ramping at 20Hz/S meant that the result was always 20Hz out, and I also needed faster ramp rates which meant even more error.

The next method was to use the standard frequency function and incremented the frequency in a loop. This also had problems as the standard function switches the output on and off in each loop causing glitches in the output which causes instability.

I also noted that switching between standard function & sweep function also gives glitches. 

The final method I found which works best is estimate the frequency as it ramps. As soon as the sweep function starts within LabView you can start a 'for loop' counting the frequency in steps of 1 Hz or so, with a loop wait time equivalent to the ramp time/number of steps. Then passing the estimated frequency out of the loop via a global variable which can be read elsewhere.

[alpha1]

Hi Steve,

Unfortunately, it does seem like there is no easy and "proper" way to do this, because of the components that make up the VI - they were created with the intention of only having one output sink. I believe the improvised method you are using with a for loop is a good way to attemp getting around the issue.