usb-9211a temperature resolution using type K TC.

[DataControl]

I was looking at using a USB-9211A for doing some TC measurements using a type K TC. One thing I can not find in any of the 9211A documentation is the true temperature resolution of the 9211A. I was looking for something like .01 C resolution as I already have a .025 C data collection device that I am looking to replace as I need slighly better resolution. Thanks for any help.

[Nathan_R]

Hi DataControl,

The accuracy of the USB-9211A using a K type thermocouple can be found on page 17 of the USB-9211/9211A User Guide and Specifications. The resolution in ˚C of the 9211A can be calculated. The 9211A has a 24 bit ADC with a +/- 80mV range. This means that the smallest theoretical change in voltage it can detect is 160mV/2^24 or 9.537 nV. Since K type thermocouples are 39.48 uV/˚C at 0 ˚C the theoretical resolution would be ~0.0002 C. This number however is not that important since external noise, CJC accuracy, thermocouple accuracy and so on all effect the measurement to the point that its accuracy is much less than its resolution.  The Knowledgebase Article 3PD0S4DI: The Differences Between Accuracy and Bits of Resolution explains this in more detail. Please let me know if you have any questions and take care.

Thanks,

[Wayne.C]

Nathan,

Any chance that the USB and cDAQ devices will be added to the accuracy calculator http://www.ni.com/advisor/accuracy/ on the NI webpage?

[Nathan_R]

Hi centerbolt,

At this time there are no plans to add USB or cDAQ devices to the accuracy calculator. For help calculating the accuracy of these devices I recommend the Knowledge Base article, How Do I Calculate Absolute Accuracy or System Accuracy? Let me know if you have any questions.

Thanks,