Why I get huge DC while measuring strain with SCXI 1520

[Sinha]

Hello All

I am using SCXI 1520 and SCXI 1314 TB in SCXI 1000 chassis with SCXI 1600 USB controller. I am using 10 channels to measure strain with quarter bridge-I completion. Resistance value is 125ohm, GF is 2.0.  I am using DAQmx Assistant to configure the task and calibrating the SG channels.I am able to calibrate all the channels when I uncheck 'shunt calibeartion.But I am facing two major issues

1. Huge DC level along with strain values.

2. The noise level I get is aroung 100 micro strains.

Please help me if some one has experinced same issues and resolved them.

I want to know what is noise level we can expect in SCXI 1520 and how to remove DC shift of signal. What are the strain values we can expect to measure.

S. K. Sinha

[ryan_d]

Hi Sinha,

It sounds like you might need to adjust your gain settings. You can do this by changing the range of your acquisition. Below is a screen shot from page A-2 of the SCXI-1520 User Manual. This table shows the expected error based on the range settings. If you’re range is set to +/- 10V, you can expect to see an offset error of +/- 3mV and some notable noise.

Please post back if you have any questions. Have a great day!

Message Edited by ryan_d on 02-05-2008 04:07 PM