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How Do I Program a DAQmx TEDS Task in LabVIEW?

Primary Software: Driver Software>>NI-DAQmx
Primary Software Version: 7.3
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: SCC>>Carriers>>SC-2350

Problem:
I know how to set up DAQmx tasks and global channels in Measurement and Automation Explorer (MAX) to use my TEDS-enabled sensors, but I want to do it programmatically in LabVIEW. Is there any way to set-up my TEDS DAQmx channels directly in LabVIEW?

Solution:
While MAX provides the easiest user interface for setting-up your TEDS hardware (SC-2350, SCXI-1314T, or BNC-2096) and sensors, you can accomplish all this in LabVIEW as well. However, you must first install the TEDS Library for LabVIEW 7.1. Refer to the Related Links section below for information on how to download and install this library properly.

To set up any DAQmx channel, you must specify certain parameters about the transducer from which you are reading. For example, a TEDS analog input RTD channel looks like the following:


Three key inputs to this VI (in addition to required physical channels input) are current excitation value, minimum value, and maximum value. The TEDS information stored in the EEPROM of your sensor or virtual TEDS file can supply values for all three of these inputs. Refer to the diagram and steps below:


  1. On the Function Palette navigate to NI Measurements » DAQmx - Data Acquisition » DAQmx Advanced » DAQmx TEDS » DAQmx Configure TEDS.vi and place the VI on your block diagram. Wire your physical channels control to the appropriate terminal.
  2. Wire the same physical channels control to a DAQmx Physical Channel Property Node located under the same DAQmx TEDS subpalette as the DAQmx Configure TEDS.vi above.
  3. Expand the node to include one more property. Left-click on the new property with the operate tool and select TEDS » BitStream. This is the actual binary data stored on the EEPROM of the transducer, so you must parse it to get the parameters you need.
  4. Place TEDS_Parse Binary TEDS.vi from the NI Measurements » TEDS » Hardware TEDS subpalette after the property node and wire the TEDS.BitStream into it.
  5. Next place three TEDS_Get Property VIs after the parsing VI from the NI Measurements » TEDS » Get TEDS Information subpalette. You can create constants for the property input and select the appropriate attributes for the DAQmx task you are creating. For this example, %ExciteAmplNom, %MinPhysVal, and %MaxPhysVal correspond, respectively, to the current excitation value, minimum value, and maximum value inputs for the TEDS analog input RTD channel VI.

Note that if you program your VI in this manner you can change out any RTD on your hardware without having to modify the software. All the configuration information is stored on the sensor. The properties of each type of transducer will vary depending on the TEDS template used in the EEPROM. Refer to the Related Links for more information.

Related Links:
Developer Zone Tutorial: An Overview of the IEEE 1451.4 Transducer Electronic Data Sheet (TEDS)
Developer Zone Tutorial: Reading and Writing TEDS with the LabVIEW PDA Module
KnowledgeBase 2S998A7N: What Are Plug-and-Play Sensors?
KnowledgeBase 3CO9BO8O: How to Install the TEDS Library
Products & Services: Sensors Plug&Play (TEDS)


Attachments:


setup.gif

Report Date: 12/30/2004
Last Updated: 08/16/2007
Document ID: 3GT6I2S9

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