How to change Resolution of ADC

[mertin]

Hi,

how can i change the resolution of the analog-digital converter on my NI-USB6211 from 16bit to 12bit ?

This should happen in Matlab. I'm using the Session based interface.

[crossrulz]

Why would you want to?  I don't see what you would be gaining by doing that.

[Dennis_Knutson]

To change resolution, you would need to change the DAQ device to one that has 12 bits. Silly question as far as I can see.

[mertin]

It's because of a Matlab script whitch ran with an older daq pad with a 12 bit resolution.

I have to migrate it to a newer daq pad and had also to rewrite parts of it as i needed a new interface in Matlab (session based interface as legacy based interfaced is no longer supported.

Here is a screenshot of a Voltage measurement. The blue curve is from the new daq pad and looks quite erratic. I think the reason might be the adc.

Maybe you have some ideas

[crossrulz]

This doesn't look like an ADC issue.  It looks more like a noise issue.  What are you trying to measure?  What is your sample rate?  Do you have things properly grounded?

[mertin]

I want to measure the voltage of a window motor.
I tried different sample rates, but they all look similar to the screenshot i posted. There the sample rate is 10k S/s.

I hope the everything is properly grounded

[johnsold]

Try a smoothing algorithm. You can do it yourself, use a low pass filter, or use Savitsky-Golay smoothing.

If you read the raw binary from the DAQ device, you could manipulate the bits to eliminate the 4 LSB.

Lynn

[mertin · Accepted solution]

I got the solution:
Changed the ADC range from -10 V - 10 V to -.0,2 V - 0,2 V