Should pins be grounded when self-calibrating a PCI-6052E using MAX or Traditional NI-DAQ?

[Tantaris]

I have looked through several posts and the manuals but I am getting conflicting information on my question.  For example, the post on Self-calibration in Linux indicates that there should be no connections to the DAQ.  However, the example program Calibrate_Eseries.c which came with the DAQ contains the following comments:

/*

* Pin Connection Information:
*    Ground the inputs to AI channel 1.  If the device is in
*     differential mode, tie both the + and - inputs to AIGND. If the
*     device is in single-ended mode, tie the input to AIGND.

*/

Also, does the channel setup (e.g. unipolar vs bipolar, voltage range) matter when self-calibrating using MAX?

Any help would be greatly appreciated.

[ChaisePotato]

Hi Tantaris,

The calibration procedures differ between MAX or NI-DAQ. In cases such as these, please refer back to the user manual when in doubt.

E series user manual: http://www.ni.com/pdf/manuals/370503k.pdf

Calibration procedure within MAX: http://www.ni.com/pdf/manuals/370937n.pdf

Calibration procedure for NI-DAQ: http://www.ni.com/pdf/manuals/322314b.pdf

Hope this points you in the right direction!

[Tantaris]

Hi ChaisePotato,

  Thank you for your response.  Unfortunately, I have read all three manuals but I have not been able to find an answer to my question.  They contain detailed information on performing an external calibration but I don't think they have any information on the connections that need to be made (if any) for an internal or self calibration.

[ChaisePotato]

Tantaris,

I've read them over as well and you are right, they aren't very explicit. I can confirm that the proper way to self calibrate this device in MAX is to leave all of the pins disconnected as it will self calibrate relative to the highly accurate and stable internal refernce in the device itself. Go ahead to follow the directions within the self calibrate section of the MAX user manual. If you'd like to calibrate your device using the older legacy method, then follow the instructions that you have found within the E series calibration file. That being said, I would recommend using MAX and following the respective procedures.

[Tantaris]

Thanks for the input.  Not grounding makes sense to me if it is being calibrated with respect to the non-zero internal reference voltage to adjust both scale factor and bias.   But if self calibration is only adjusting the bias, I could see where you would ground the inputs.  I'd really like to know exactly what is going on under the hood.

[ChaisePotato]

Could you clarify what you mean by adjusting scale factor? In all of the documentation that I have encountered, the best practice for self calibrating this device is accomplished through MAX without grounding any of the channels. What exactly are you trying to acomplish that this method might not work for?