6008 accuracy

[Ivanek]

Hallo

I have a problem with NI USB 6008 card. Accuracy of device is very bad. I attach excel file with comparison between NI and KEITHLEY. Number of samples is not the same because KETHLEY have a longer time to measure.

The behaviour must be almost linear as KEITHEY measured.

I have similar situation with some NI analog card.

Do You have a some suggestion of that ?

Best Regards

Ivanek#

[devchander]

You are comparing a 12 bit DAQ card with six and half digit ( 22 bit resolution) DMM.

That is not a fair comparison!

If you want to improve the accuracy of USB DAQ card, you can do a few things like select a more optimal Analog input range, go for ideal signal connection mode for that signal( Differential/single ended)

[AnalogKid2DigitalMan]

If you need the performance of the Keithley, why not get a GPIB card and connect it to the Keithley (or serial or USB as alternatives). Assuming yours has some form of communications I/O.

[Travis_W]

Hi Ivanek,

As mentioned, Instrument Control via GPIB could be a great answer for you application.  In addition, National Instruments also has a variety of products that can acquire analog signals with very high resolution. 

For applications that require high accuracy, we offer DMMs in both the PCI and PXI form factor that have up to 26-bits of resolution.
Also, the award winning PXI-5922 Flexible Resolution Digitizer offers 24-bits of resolution at sample rates up to 500KS/s ranging to 16-bits of resolution at 15MS/s.

Let us know if the suggestions from this thread don't help you out, or if you need more clarification on any of them.

Have a great day!
Travis W

Message Edited by Travis W on 08-31-2006 05:46 PM

Message Edited by Travis W on 08-31-2006 05:47 PM

[Ivanek]

Yes. That is true. After "devchander" post I saw a video about DAQ.

In my first attachment was comparison between HW averanging values from KEITHLEY and no averanging with NI USB-6008. I apopogize for that.

I acquire only one sample !

I using LabVIEW 7.1 and after that I try to set different setup USB-6008 (N samples) and I got 10 000 samples / 1s. After that I made one averange value from N samples by LabVIEW. Accuracy is very good now for me.

Is possible to setup USB-6008 to get one averange sample (like KEITHLEY) from USB-6008  ?

Thanks for answer

Best regards

Ivanek#

[devchander]

Averaging the acquired data samples on LabVIEW as you have already explored, YES you can

But you cannot set the DAQ board Hardware itself to give out an average of 'n' number of acquisitions

Message Edited by devchander on 09-01-2006 01:20 AM

Message Edited by devchander on 09-01-2006 01:20 AM

[Travis_W]

Ivanek,

Devchander is correct, there is no hardware averaging available on the 6008. 

The reason for this is that you have access to all the raw data in software, so you can manipulate it in any way that your application requires.  This gives you the flexibility to do averaging, as well as customized filtering, signal processing, advanced analysis and display.

Again, if you have any more questions, don't hesitate to let us know.  Best of luck on the application.

Have a great day!
Travis W

[Ivanek]

Yes

I understand now 🙂

Thaks everybody for explanation.

Best Regards

Ivanek#