Thermocouple channel NOT valid

[Rowlini]

I have a DAQCard-AI-16XE-50 connected to a SC-2345 that I set up to use with DasyLab 5.03.34 on a Win2000 (Ver. 5.00.2195 SP 4) IBM ThinkPad. A week of testing was done recently and everything worked as expected. Today I opened the Measurement & Automation Explorer (Ver. 3.0.2.3005) and found that all 5 of my thermocouple channels NOT valid. When I open the Test Panel, I find the error 10007 occurred at AI Group Config. I have searched the MAX  help and online FAQ's for help on this. I tried "Reset driver for Traditional NI-DAQ". Can someone advise me what action I could take to get these channels working again.

Not that MAX cares, but I believe I used the "National Insturments: AY-MIO Series" driver in DasyLab. The other drivers I have available are: iotd32_e.dll, IOTdrv32.dll and NI_DRV32.dll. Which of these should I be using?

[Rowlini]

A couple more questions while I'm at it. What is the preferred input mode for TC's? (Differential, RSE, NRSE) I understand that I actually use 2 channels for each TC (x & x+8) to enable the CJC compensation. However, the only CJC sources I see are User Supplied and User Value. I thought there was a third choice, like internal CJC. Where have I gone wrong here?

[Robert_F]

Hello Rowlini,

I am assuming that you are Right-Clicking on Traditional NI-DAQ under Devices and Interfaces in Measurement & Automation Explorer (MAX) and selecting “Reset Driver for Traditional NI-DAQ” to reset the driver.  What do you mean that all 5 channels are not valid?  Are they not valid because you are getting error -10007? Are you getting this error through a test panel?

What test panel are using to test your DAQ board?  Are you using the test panel for the device or the test panel for the virtual channel?  I would use the test panel for the device first and make sure that you are acquiring the raw data correctly.  Then open the test panel under virtual channel to verify that all the settings are correct. 

This error might be created because the settings are not set correctly in the virtual channel.  I would suggest double checking those values.  Make sure that your virtual channel is using the correct analog input mode.  (Differential or Referenced Single Ended)  Do you have the correct channels selected if you are using differential mode?

[Rowlini]

Hi Rob,

I did do the reset the way you described. My first clue that there was a problem was a small red "X" by each TC icon. When I entered the test panel for each of them, the reading was full scale and the red error dot was lit. By clicking the error button I discovered the error number.

This morning I started from the beginning and re-created all the channels. The X's are gone and everything seems to work fine both in MAX and DasyLab. This time the option to use the "Built In" CJC IS available but the only Input Mode is NRSE for both the TC channels and the voltage channels. I don't know why that is.

I read a number of FAQ's regarding setup but I'm still not clear on the preferable Input Mode for the various channels. Differential is better in regards to CMR properties but uses 2 channels. I read that with Differential and NRSE, balancing resistors should be used. I would prefer to avoid this as I don't seem to have any noise problems. I have 5 TC01's, a LP01 and an AI14 installed in J1 through J7 (ACH0 - 7). The way I understand it, the TC01's use the X channel for the measurement and the X+8 channel for the CJC. The LP01 and the AI14 also use X and X+8 for 2 separate inputs. Is that correct? Is there a way to only monitor one CJC channel thereby freeing up some X+8 channels?

Is there a preferred Input Mode for for the various modules? Given that the modules run on the same power supply as the DAQCard (ie laptop power), I would assume that the inputs are referenced to the supply already.  Wouldn't I only need to use balancing resistors when I want to monitor a voltage that is NOT derived form the laptop (ie vehicle power for example)and is NRSE or Differential? Thank you for taking the time to help me out with this.

[Robert_F]

Hello Rowlini,

 Normally, you would prefer to measure your sensors using differential mode.  This mode will try to eliminate as much noise as possible.  The problem with this method is you have effectively reduced the amount of channels from 16 to 8.  The TCOX modules will actually measure the thermocouple using a differential amplifier circuit and measure the CJC.  The differential measurement is then passed to DAQ board on AI (X) and the CJC measurement is passed to the DAQ on AI (X+8).  There is CJC data is always passed to the DAQ board on AI (X+8) with these modules.  There is a great circuit diagram explaining how the modules operate on page 5 of the SCC-TC Series Thermocouple Input Modules User Guide.

You would then use Reference Single Ended mode to measure the Thermocouple measurements on the DAQ board.  (They were differentially measured on the module)  There is a great explanation of the different measurement modes in chapter 4 of the AT E Series User Manual.  The biases resistors are not necessary; however it might become useful if there is a lot of noise on your signal.

Here is a great KnowledgeBase outlining the process of setting up a SCC-2345 with Traditional DAQ.