SCXI-1520 Excitation External Cal

[Zorchmaster]

I've successfully performed an external calibration of the gain and offset coefficients on my SCXI-1520 using the NI-DAQmx calibration VIs.  However, there doesn't seem to be a way to adjust the excitation EEPROM constants using the DAQmx API.  The SCXI-1520 Calibration Procedure lists two C calls, SCXI_Adv_Module_Write and SCXI_Adv_Module_Read in Traditional NI-DAQ but there aren't any function prototypes listed in nidaq.h.  I found the actual functions in nidaq32.dll using Dependency Walker but without the prototypes, I'm just guessing at the argument list.  Are there any undocumented arguments to the DAQmx VIs or even a way to use SCXI Cal Constants.vi to get to the excitation constants?  The actual excitation values themselves are within the "nominal setting" spec but the values returned by the driver are not in spec.

-Bob

[Zorchmaster]

By looking at the .lib and .dll files, I figured out the function prototypes for SCXI_Adv_Module_Read and _Write.  I'd like to be able to call these from LabVIEW but C will have to do for now.  Is there a way to directly call nidaq32.dll functions from LabVIEW?

But more importantly, the Actual Excitation Value property for the SCXI-1520 doesn't seem to work correctly.  It always returns a nominal value instead of the calibrated value from the device EEPROM.  I tried it in both C and LabVIEW and it always returns the same value.  I thought this property was supposed to return the actual device calibrated excitation value.  I'm using NI-DAQmx 8.8.

-Bob W.

[Mr.F]

Hi Bob,

Looks like you’ve made a bit of progress on the matter. Can I pull your email information from our databases and email you directly? We can discuss your application a bit further and there is a document I’d like to send you.

[Zorchmaster]

Sure - go ahead.  Thanks!

-Bob

[WTCal]

I would like to get the actual excitation value store in the SCXI-1520 EEPROM using DAQmx.  Legacy DAQ code returns this value when you call SCXI_Set_Excitation.

Thanks,

Calvin

[Justin__D]

Hi Calvin,

Currently, there is no DAQmx vi that can do this.  However, it may still be possible to get this information from your 1520 module.  This link explains this a little more.

How Can I Retrieve an SCXI Module's Calibration Constants?

On a side note, in the future it would be best to start a new discussion thread.  Even though this is a similar topic, it has been inactive for quite some time so most users will not be monitoring it.  For a quicker/better response, a new thread would be beneficial.

I hope this helps.

[Brad_K]

By the way, you can also measure the SCXI-1520's excitation using the _pPos0:7 and _pNeg0:7 internal channels. When you perform a shunt calibration, NI-DAQmx does this and stores the result in the AI.Excit.ActualVal property, but you can also acquire from these internal channels directly.

Brad