High speed DC measurement with Agilent

[MarioSan]

Good morning everyone,
I'm trying to configure my agilent 34470A to acquire the maximum number of points in DC.

From the characteristics it appears that my Agilent can in theory measure 50000 read/s however I can only display about 8000.

 

Operation is as follows:
I connected my function generator to the multimeter.
The generator generates a sinusoidal function at 1 Hz with an amplitude of 8 volts DC.
I read and export the sampling points in an excel file.
If I went full speed I should get 500,000 points in one second and see ONLY one full period of the wave but that's not the case.
If I set 50000 points, I see about 3 whole periods.
I no longer know which parameters to act on to increase the reading speed.

Every suggestion is accepted.
Thank you

[santo_13]

It would help if you could attach your VI to capture the data points.

Typically, for high-speed acquisition, there is a limited onboard memory on an instrument which you need to continuously empty not to overflow and lose data, if you miss to quickly read, in the end, you will be left with only the size of the onboard memory. You can get more information on these numbers from your instrument manual.

[cstorey]

You/ve set the read timeout to 50000ms, that won't give you 50000 readings.  Using the "Multipoint Acquire VI" inside a while loop to make the measurement repeatedly, and transfer the data to the PC - that's slow.  On top of that also writing data to Excel in a file is not a fast process!  I'll bet those 5 periods you are seeing aren't a continuous datastream, but a bunch of readings happening every 50000ms when the Multipoint Acquire is timing out.  

Here's a few tips..

- remove the while loop

- Use the Measurement Count on the Multipoint to get the number of points you require.  ( But if this doesn't work look for limitations within this VI!! )

- Be sure to set the timeout to something very long.  The measurement of 500,000 points might be fast, but transferring that much data over USB/GPIB isn't fast.  Give it a timeout of 1-2mins.

- read all points back into an array, count number of point.  If its less than expected increase the timeout. 

- it should look something like below..

Craig

[MarioSan]

Thanks a lot for the answer,
I would like to have your brilliant experience already!
I tried to delete the outer While loop but still can't get 50000 points in one period.

The result in Excel shows about 35000 points and about 7 swings:

I would like to first save the 50,000 points in the instrument's buffer memory and then read them and put them in excel but unfortunately I don't know how to do it.
I'm still a landslide with LabvieW, I'm trying to learn.

I attach my VI here.

Do you have any suggestions?

[Sebastian.Weber]

Hi!

Are you sure your multimeter can do 50.000 samples per seconds?

I don't know the Agilent (?) 34470A, but use the Keysight 34465A, which should be pretty much the same. That multimeter used to be limited to 5.000 samples per second, and there was a software license to get the full 50.000. However, there is now a firmware update which also brings the 50.000 for free.

I also observed that before the update, when set to 50.000, the multimeter will actually use its maximum of 5.000 and record slower, but longer. This would explain your three periods. Maybe you collect available values before the entire measurement is done?

Also, there is a limit of how many values can be stored (don't know how many), wich can be extended to 2 millon by a software license (not included in the new firmware)