Setting up a strain scale

[jwhite]

I am trying to set up a map ranges scale for a load cell and I cannot obtain accurate readings (i am using a test weight to verify).  I need to know how to set up these scales based on the characteristics of the sensor.  The load cell I have has the following: 0-5lb range; max excitation nom 10V, max 15V; rated output 2 mV/V; zero balance .0056 mV/V.  For signal conditioning,  I am using an SG-24 SCC module inside a SC-2345 chassis.  In my scale, the pre-scaled units are strain and scaled units are lbs.  How do I correlate the "prescaled" max and min values to the "scaled" max and min values to get the correct readings? 

This is helpful to know how to do when using strain type sensors such as pressure and load. 

Thanks for your help!

Jason

[Justin_M]

Hi Jason,

Are you setting up a strain task?  If so, it should be pretty straightforward to set the properties of your load cell (gage factor, gage resistance, etc.)  in Measurement and Automation Explorer (MAX):

Once you have your settings correct, you can create a new scale by clicking on the Custom Scale dropdown and selecting Create New...  This will allow you to create functions or tables to map your prescaled values to the correct scaled values.

Thanks,

Justin M.

National Instruments

Message Edited by Justin M. on 07-13-2006 06:27 PM

Message Edited by Justin M. on 07-13-2006 06:27 PM

[jwhite]

Ok, how does that help?  I specifically asked for assistance with setting up a custom scale, not getting my settings correct.  Once again, I need to know how to set up the "prescaled" max and min values and the "scaled" max and min values for a Map-Ranges scale.  The parameters of the sensor are in the previous post.

[Justin_M]

Ah, I must have misunderstood your question...

Take a look at the following KnowlegeBase articles.  I believe they have the information you need:

How Do I Get Appropriate Readings Using a Load Cell?
What Do the Units Millivolts per Volt of A Load Cell Mean?

Thanks,

Justin M.
National Instruments