excitation source for thermistor

[penn_mc]

I need to measure temperature with a 30Kohm (@25C) thermistor and NI 6009 USB.

I don't know what to use for external excitation current. I wonder if I could use the 6009 AO channel. If so, I am not sure how to hook it up.

I will appreciate your help.

Maria

[Stephen John]

The NI6009 should have a +5V fixed output. At its most simple, you could use a fixed resistor in series with the thermistor, powered by the 5V source. Then use an AI channel to measure the voltage and calculate the temperature. See other pages, such as http://www.embedded.com/story/OEG20020125S0100 for more circuit details.

[penn_mc]

Hi Stephen,

Thanks for replying. I used the DAQ assistant to create a task that generates +5V continously but it only lets me select "on demand" samples. There is some conflic with the timing clock that does not allow me to select "continous samples".

I will appreciate some help on the configuration of the task.

Thanks a lot,

Maria

[jack47]

I think he is referring to a pin that has +5V from the USB power.  Pin 31.  It doesn't need to be configured.

[penn_mc]

I got it!

Thanks a lot for your wondeful help!

Maria