K-type Thermocouple with USB-6008

[efinstrom]

I'm working on connecting a K-type thermocouple to a USB-6008 DAQ device.  I'm having trouble getting a good voltage signal that compares with my handheld voltmeter.  I have read other threads that say that this DAQ system is not good for thermocouples.  But there must be some way to make it work at least marginally.  Any help would be appreciated.

[Justin_M]

efinstrom,

The problem is that the USB-6008 was not designed for the very small voltages generated by thermocouples.  The 6008 has 12-bit resolution and a minimum range of +/- 1 volt.  This gives a voltage resolution of about 490 microvolts:

voltage range / 2^(# of bits) = 2 / 2^12 = 0.000488

A K-type thermocouple outputs about a 40 microvolt change for every degree Celsius.  This means that the 6008 can only measure changes of more than 10 degrees Celsius, which is why it is not recommended hardware for thermocouple measurements.

National Instruments does offer many products that are great for measuring temperature.  Visit http://www.ni.com/temperature/ if you are interested in finding out more.

Thanks,

Justin M

Applications Engineer

National Instruments

[AlexejWisner]

If you with USB-6008 measure the temperature with Termoelement type K willlst, you must use an isolating amplifier or a transducer. For example: MCR-TE-JK-U of https://eshop.phoenixcontact.de/phoenix/logon.do?user=anonym&callingPage=start.