lowest voltage PCI 6251 can detect

[Samax70]

I am interested in purchasing the USB 6251. I do not have alot of experience with setting up a DAQ systems. I was hoping someone could explain to me how I can determine if the board will read my voltage input without signal conditioning. I see the card has programmable input ranges from +- .1v to +- 10v and I wanted towould to know how I can figure out the lowest voltage I can expect to see with the 6251. I am going to be using TC's and expecting around 200mV range. Can some shed some light please?

[TCPlomp]

Hi Samax,

the 6251 is a 16 bit ADC so the whole range will be spread over 2^16-1 elements:65535
so in the +- 0.1 V the bit resolution is 0.2/65535 3.05 uV. For your signal of .2 V you should use (out of safety) the +- .5 V and then the bit resolution is 15 uV

Ton

[David S.]

Hi Sama -

Ton is absolutely correct, and I'd like to provide some documentation that will help you with your selection.  The M Series User Manual contains a full chapter on configuring devices for analog input measurements.  Page 4-2 (pdf page 40) begins a section that fully describes the available input ranges and sensitivities.

[Iran]

Hello...

Have same problem  here regarding a load cell  with same  values.. where all these Data you comment have to be configured? ..

regards

Iran

[David S.]

Hi Iran - 

The manual can now be found here.  The easiest way to find it, in general, is to navigate to ni.com/manuals and search for it using faceted navigation.

Load cell measurements usually require quarter- or half-bridge completion, and sometimes excitation to the sensor.  Are you using any signal conditioning equipment to do this, or simply trying to measure the sensor directly with your DAQ device?  What physical connections have you made between the sensor and the device?  This article (and the links it extends to) may help you with setting up your system.