Does DAQmx handle TEDS calibration templates?

[DAD]

I've had no luck finding any info on this in what little NI documentation exists on TEDS and thought I'd try asking before running experiments to figure it out.  If I have a TEDS sensor and include a calibration template (ID 40, 41, or 42) will DAQmx properly apply the calibration from the TEDS?

[Tom_W_[DE]]

Hi DAD-

NI-DAQmx does handle TEDS directly with both programmatic channel creation and through the MAX interface.  This KnowledgeBase is a good reference for programming with TEDS in LabVIEW.  Some of the VIs used in that example are not installed automatically with NI-DAQmx but are available as a free add-on as described in this KB.

If you are looking for more general information about TEDS you may want to check out this DevZone Tutorial.

Hopefully this helps-

[DAD]

Tom, Thanks for the reply.

But I think that your statement that DAQmx handles TEDS directly is misleading.  Consider the following:

Since I'm working with SCXI-1520 and SCXI-1314T hardware my discussion be slanted towards strain gages.  I've configured 4 different TEDS EEPROMS with the strain gage template (ID=35), with unique values for physical min/max, electrical min/max, nominal excitation, and bridge resistance.  I have a simple VI that consists of a DAQmx Create Task followed by a DAQmx Configure TEDS followed by a DAQmx Create AI Channel TEDS(sub) (I extracted this from the DAQmx Create Channel (TEDS-AI-Strain-Strain Gage) to eliminate the effects of the property node in the parent VI) followed by a channel property node (to observe the min/max, bridge resistance, etc.) followed by a DAQmx Clear Task.  When I run this VI on one of my channels, it is clear that the physical min/max and excitation levels from the TEDS are not propagated to the channels properties by DAQmx (based on the property node in DAQmx Create Channel (TEDS-AI-Strain-Strain Gage) this is what I would expect), but the bridge resistance is (i.e. the value from the TEDS is displayed). 

Another situation arises when dealing with the Gage Type and Type of Bridge entries from the template.  The Type of Bridge is straight forward, either quarter, half, or full.  But the Gage Type values available in TEDS provide many more possibilities than the types provided in DAQmx (Full Bridge I, II, III, etc.).  If I set up a TEDS template for rosette, I get readings from the VI, but don't know if it's really using the information from the template.

So when I'm using the DAQmx Create Channel (TEDS-AI-Strain-Strain Gage) in my code, do I assume that the only parameters I need to pull out of TEDS myself are those necessary for the inputs on this function and it will extract any other fields it needs itself?  How can I tell which fields from the template are being used by DAQmx?  Do I need to explicitly pull out all the fields that apply and use property nodes to get these values into DAQmx?

I think most of this all boils down to a lack of detailed documentation.  I could run lots of experiments, but can't afford to invest the time.  So it looks like I'll have to pull all the fields from TEDS myself and use DAQmx function inputs and property nodes to try and make sure each channels is configured correctly.  But if I have to do that, what's the point of having the TEDS variations in the DAQmx Create Channel function?

[Tom_W_[DE]]

Hello-

I think there may be some confusion on the implications of min/max with NI-DAQmx.  While the strain gauge may suggest its possible limits in its TEDS datasheet, the NI-DAQmx min/max controls are used to configure various settings for the DAQ hardware, most notably channel gains for both the SCXI-1520 and the DAQ card itself.  These are driver-level limits and not a hard restriction of the sensor, so in order to manipulate these values with respect to the NI-DAQmx task you should set them with the DAQmx Create Channel instance you choose.  Other sensor-specific values such as gauge resistance should and will propagate over to the task as you have already seen.

DAQmx provides all of the major "type" variations for each of the three main bridge configurations.  The possible configurations are shown in the AI.StrainGage.Cfg DAQmx Channel property node as shown here:

However, NI-DAQmx does not include rosette gauge support.  I would encourage you to file a product suggestion for consideration by our R&D engineers.  This would also be a good forum to suggest more complete TEDS documentation for NI-DAQmx.

Hopefully this helps-

Message Edited by Tom W. on 10-04-2005 12:29 PM

[DAD]

Tom,

I commented to several R&D engineers last year about the state of the documentation but not much has changed since then (my guess is because TEDS isn't a big part of NIs business, so resources have been re-allocated to other areas and there isn't any ongoing development/improvement). 

Ok, I'm done whining, I'll go finish my code now.

[Tom_W_[DE]]

Hi DAD-

I can understand your frustration, but I would still encourage you to file your request online.  Product Suggestions are forwarded directly to the decision makers within the R&D structure.  That would definitely be the best route to have your requests heard.

Thanks again and best of luck with your app-