NI USB 6008

[tajim]

Dear All!

I am looking for help on NI USB-6008. I am trying to set up 4 K-thermocouples by using 4-channels of this USB-6008. I have made an express VI in the Labview 8.5 and I have setup all these 4-channels in this VI. The VI is attached for your review!  Coming to the problem!! I am getting strange readings of these 4 channels even if I have no thermocouple plugged in to the screw terminals of this USB-6008. Please help me and explain what is happening?? Why I am getting these strange temperature readings while there is no thermocouple plugged in??????

Regards to All!!

Tajim

[tajim · Accepted solution]

Dear All,

I am sorry for not attaching the screenshot of this setup! Here it is this time!

Regards!

Tajim

[Dennis_Knutson]

You've marked your last post as the solution. Does that mean the problem is solved?

If not, your image really does not tell anyone much. Reading channels with nothing connected is not supposed to give anything. If you have incorrect/inconsistent readings with the thermocouples connected, that is different though the 6008 is a poor choice for this type of measurement.

[tajim]

Dear Dennis!

The problem is not solved yet! The solution button was pressed by mistake!!

Well! I have been reading posts on this poor ability of USB 6008 to read thermocouples!! I have tested it my self too! But in principle this board must read any voltage coming out from the thermocouple. *How accurate*, is another issue!! When I failed reading any sensible value of temperature from this board at room temperature, I thought of checking the board by not plugging in any thermocouple and yet running the VI with these channels configured as thermocouples in DAQ Express VI (which is attached in my previous post)!! You can see these temperature readings in one of the graph (top left). I hope to have your comment on why there is such a response from USB-6008?

Regards!

Tajim

[Dennis_Knutson]

As I said, checking anything with the inputs disconnected is not valid. Do a search for 'ghosting' to see problems with floating inputs. If you want to check the 6008, you can ground the inputs or apply a fixed voltage. Then connect back the thermocouples and if you still have problems, provide some details on how you actually have made the connections and what sort of readings you get. 

[hamid7180]

HI All

I have question about USB 6008.  I like to generate two TTL signal from USB 6008 that I call them (fire and stop) for triggering MCA card. it is important to repeat this (fire and stop) periodic  for example 10 times. the other issue is time between each (fire stop).I need 30 Seconds time to next (fire and stop) signal.  How can I generate this task using USB 6008?

[smoores]

hamid7180,

This thread that you have posted on is over 5 years old.  You may recieve better response from the community by creating a new thread.

Unfortunatelly, the device you are using is one of our lower end products, and is not capable of pulse train generation.  You could, however, try using a digital output task to create your pulse train.  Take a look at the NI Example Finder under Hardware Input and Output -> Digital Output.  You may be able to pull it off by creating an array of boolean values, and outputing them based on some hardware clock rate you define.  For example, if you were able to achieve a 1 Hz clock rate on the 6008, then you could create a 2D boolean array for your 2 digital output lines.  You could set it to something like, 1 followed by 59 zeros on the first row, and 30 zeros followed by a 1 followed by 29 zeros on the second row.

Does that make sense?

[Dennis_Knutson]

A hardware clock rate is not an option with the 6008. The only option is software timing where you would use delays/wait statements between writes. This would be subject to some jitter because of Windows.

[hamid7180]

Hi S. Moore

Unfortunately, NO

I have created another topic here