K-type thermocouple with usb - 6009

[john_Cheung]

Dear all,
Hi. I am a new user. I am now using Labview 8.0, a K-type thermocouple and NI USB-6009 Multifunction DAQ. I want to measure temperature with the thermocouple.
I use the example vi found in : http://zone.ni.com/devzone/cda/epd/p/id/4996

But there are some problems. First I get random result. I searched the other topics and someone pointed out that using AD590 chip could ampify the signal from the thermoocouple. I searched the RS web site and got this http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5228641
Is this the one I needed?

Second, I only want to have a reading per second. Can I change the output to numeric one but not the array one? If yes, how can I do? 

Besides, can I use a humidity senor with usb 6009? I find that it is rare to use humidity sensor. Does anyone has experience ?

Please help

Message Edited by john_Cheung on 01-12-2009 07:23 AM

[john_Cheung]

I tried the program for sometime and some problems were fixed.
But the random result of temperature data is still remain. The range is from +ve 200 and -ve 1000.
Can anyone help?

[Chris_W.]

Hi John,

The USB-6009 is not really meant for thermocouple measurements, which means it doesn't have cold junction compensation (CJC). That is probably why someone had suggested you get the AD590 temperature transducer.That is a good solution to get around not having CJC. You will want to connect your thermocouple to one of your analog input channels in differential mode and connect the temperature transducer to another AI channel. When you create your analog input temperature task, you can set the CJC source to "channel" and specify the channel that you have the AD590 connected to. This should work out for you.

Another thing you should be aware of is that the minimum voltage input range for the USB-6009 is ±1V. Make sure that this is going to be ok for your input signal range.

Chris W