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dynamic range


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3 replies to this topic

#1 Guest_Dallmann_*

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Posted 01 September 2004 - 07:56 AM

What is the dynamic range of the labjack U12?

#2 LabJack Support

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Posted 01 September 2004 - 08:08 AM

Please expand on your question, as there could be various interpretations of what is meant by dynamic range.

You also might find you answer by looking at the last 2 items in our basic FAQ which describe the U12s 12-bit resolution and PGA:

http://www.labjack.com/basic_faq.html

#3 juancho

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Posted 17 July 2014 - 01:19 PM

Hi, I have the same question about U6. Will the Dynamic Range be: DR=20*log(20/(20/2^16))=96.33 dB? This with 16 bit resolution and +-10V range (Gain=1).

 

Thank you,

 

Juan Manuel

Bogotá, Col



#4 LabJack Support

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Posted 17 July 2014 - 02:44 PM

Looks like you are wanting to express resolution in dB rather than bits, and I would agree that 16-bits corresponds to 20*log(2^16) = 96.3 dB.

 

That answer makes sense, because 20 dB is a factor of 10, so we could write equivalencies like the following:

 

10 counts =>  1:10 =>  20 dB

100 counts =>  1:100 =>  40 dB

1000 counts =>  1:1000 =>  60 dB

10000 counts =>  1:10000 =>  80 dB

100000 counts =>  1:100000 =>  100 dB

 

16-bits provides 2^16 or 65536 counts, and that is between 10000 and 100000 so it makes sense that the dB is between 80 and 100.

 

The U6-Pro (and T7-Pro) has a 16-bit ADC and 24-bit ADC.  Expressed in dB that is a 96.3 and 144.5.  As we discuss in the following app note, however, the stated resolution of an ADC is not super important:

 

http://labjack.com/s...-and-resolution

 

It is more important to include noise so you have an idea of the resolution you can actually acheive, and we provide this information in Appendix B of the U6 User's Guide:

 

http://labjack.com/s...uide/appendix-b

 

The downside to increasing ResolutionIndex and Gain is that the time per sample increases, as reflected in Section 3.1:

 

http://labjack.com/s...users-guide/3.1

 

For example, with ResIndex=1 and Gain=1 (max data rate settings) the noise-free resolution is typically 14.0 bits (84.3 dB) and the effective resolution is typically 16.1 bits (96.9 dB).  By the way, these numbers are excellent compared to most other 16-bit ADCs ... better than most if not all.




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