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Channel Numbers


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#1 Aro

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Posted 12 June 2015 - 09:14 AM

I am using a UE9 to monitor thermocouples and control a few SSRs, and due to space requirements it must be done using the screw terminals on the UE9 itself.  I have two LJTick-InAmps on the 4 AIN channels to monitor 4 thermocouples, but I need to monitor a 5th thermocouple and so I have a 3rd LJTick-InAmp on the FIO0 and FIO1 channel block.  My question is how do I number the channels in DAQ Factory?  I know that the AIN channels are numbered 0-3 and have an I/O Type of A to D, but the 4 FIO channels also are numbered 0-3 and in order to read thermocouples they also must have an I/O Type of A to D.  Wouldn't this mean that there would be two channels both numbered 0 and A to D?  What am I missing?

 

Thanks in advance



#2 LabJack Support

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Posted 12 June 2015 - 10:07 AM

The detail is that FIO lines on the UE9 are digital only.  When you specify AtoD in DAQFactory, that means you are using AIN#.  You will need to go through the DB37 connector to get at more analog inputs.  To use the LJTick-InAmp you will have to figure out some way to get it connected anywhere between the DB37 and the thermocouples.  Without the LJTIA, the UE9 can get thermocouple resolution on the order of a degree or 2.



#3 Aro

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Posted 15 June 2015 - 11:06 AM

I'm still new to all this, so bear with me as I try to get a little more clarification on the two options.  

 

Using an LJTIA:  I get that the VS and GND pins of the LJTIA would go to the VS and GND pins of the DB connector, but what about the OutA and OutB pins?  They should go to any two AIN pins in the DB connector so long as its not AIN0-3 (since I am using those on the UE9's screw terminals)? 

 

Direct wiring: If I wire the thermocouple directly to the DB37 should I still use a 10kOhm resister between the negative lead and GND?  And to get the temperature I should apply the conversion to both AIN channels and then subtract the reading of the negative lead from the positive lead, or do I determine the difference first and then apply the conversion?

 

Thanks for all the help



#4 LabJack Support

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Posted 15 June 2015 - 02:01 PM

 

Using an LJTIA:  I get that the VS and GND pins of the LJTIA would go to the VS and GND pins of the DB connector, but what about the OutA and OutB pins?  They should go to any two AIN pins in the DB connector so long as its not AIN0-3 (since I am using those on the UE9's screw terminals)?

 

Correct.

 

 

 

Direct wiring: If I wire the thermocouple directly to the DB37 should I still use a 10kOhm resister between the negative lead and GND?

 

No, just connect the negative lead directly to GND.  If the UE9 supported differential readings you could consider the other method, but it does not.

 

Make sure you avoid complication #5 from the Thermocouple App Note:

 

http://labjack.com/s...s/thermocouples

 

 

 

 

And to get the temperature I should apply the conversion to both AIN channels and then subtract the reading of the negative lead from the positive lead, or do I determine the difference first and then apply the conversion?

 

You will just do a single-ended reading of the channel the positive is connected to and that will be the thermocouple voltage.

 

Also, for the best results set that AIN to use Range=0-1.25 and ResolutionIndex=17 (or 18 on a UE9-Pro).

 

https://forums.labja...p?showtopic=674




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