Problems with PCI-6221 Analog Output Range

[hongbo]

Hello,

I am now using a PCI-6221 to give single-update voltage output for a controlling device. I need the output range to be 0-2V. Unfortunately, what I got was only 0V to 0.45V. I tried dozens of ways to find out where goes wrong by changing everything that can be changed on both software and hardware, even using the nidaq32.dll by hand (so I don't wanna an answer that 'please change or check blahblahblah'), and I confirmed that the problem comes like this: when running in LabVIEW by specifying lower/upper limits and the output values, there is no error code return, and the output goes linearly from 0V to 0.45V, however, it NEVER goes higher than that when I command LabVIEW to do so. Therefore, the DAQ card must have some problems with its internal AO range supplier. (-10V to 10V). I would also have tried the external reference, unfortunately this cheap card does NOT allow me to do so.

What I must mention is that, the card was purchased just one week ago and in the first days I didn't discover this problem before my boss transfered the payment. So now I have 90% fear that it might go back to NI factory to be examined and repaired there.

So I'm looking forward to the genius answers from anyone.

Best regards,

Hongbo

[hongbo]

Attaching the diagnostics result file:

Using the newest released DAQ diagnostics program, running with DAQmx 8.1

An additional info: I'm using the BNC2110 connector box, which might also have an upper-limit cut-off

Hongbo

12_12_2005 21_09_59

Results saved to:  C:\Dokumente und Einstellungen\User\Desktop\Hongbo\Diagnostic Results.txt

Selected Device: Dev1

Device Type: PCI-6221

Serial Number: 11D09A2

Device Support: (PASS)

NI-DAQmx Version: 8.1 (PASS)

Device Reset: (PASS)

The device was last self-calibrated on: 12_12_2005 19_33_33

Running Calibration ...   (PASS)

-------------------- Testing Counters... --------------------

Testing CTR Buffered Pulse Generation...   (PASS)

Testing CTR Single Pulse Generation...   (PASS)

-------------------- Testing Analog Input... --------------------

Testing AI Ground Reference...   (PASS)

Testing AI Voltage Reference...   (PASS)

Testing AI Finite Sample Clock...   (PASS)

Testing AI Finite Sample Clock Frequency...   (PASS)

-------------------- Testing Analog Output... --------------------

Testing AO Finite Sample Clock...   (PASS)

Testing AO Finite Sample Clock Frequency...   (PASS)

Testing AO Single Point...   (PASS)

Testing AO Accuracy...   (PASS)

-------------------- Testing Digital IO... --------------------

Testing DIO Lines...   (PASS)

Testing DIO Ports...   (PASS)

 ----- DIAGNOSTIC TEST COMPLETE -----

[hongbo]

Geez... after fighting for some time I finally found the reason.... the driving cabability of the AO channel is not powerful enough...my instrument has some kind of 0.45V bias at its input port and the DAQ card can't push higher than that... I gonna do some electronics work to shoot this trouble

[eceumn]

Hi hongbo,

Could you tell me how you program to generate single-update voltage output. Thanks a lot.

[devchander]

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Could you tell me how you program to generate single-update voltage output

---

 Do You Mean something Like??

Generate 4 Volts-> keep the AO at 4 Volts until you programatically update it to 5 Volts??

[eceumn]

Hi devchander

Thanks for your answer. I am using labview 7.1. But I am confused with the vi file (creat channel for AO voltage) which is provided by ni. There are maximum and minimum voltage setting in the vi file. So I need to set both maximum and minimum voltage setting for 4V?

[devchander]

The Limits are to set the DAC range for your AO channel.

So for generating 4 Volts on that AO, select minimum and Maximum values in optimal range ( like 0 to 5 Volts)

look at attached VI for generating a single point update

You will find many more example vi's in LabVIEW examples at Find Examples>>Hardware input and out put>>DAQmx>>Analog generation>> Voltage folder

Hope this helps

Regards,

Dev