Properly using DAQmx scales.

[xkenneth]

What is the true proper use of a DAQmx scale?

My current situation is that I've got about 5 or more 4-20mA sensors coming in and I'd like to apply DAQmx scales to these to hand their gain and offset correction. For example let's say I've plugged in two 5000 LB Pressure Transducers and 3 2500LB pressure transducers logically I should be able to have two different scales, apply them to the proper channels and then have some way of offsetting error correction. To me this seems like the way that DAQmx scales should work properly. Instead if my sensors have slightly different calibration offsets (ie they output 4.2mA low instead of 4.0mA) I've got to have a completely different scale for each one to deal with offset correction. Should I be dealing with this in software or does this fall within what a DAQmx scale should do?

- Ken

[Wayne.C]

DAQmx scales are intended to do just what you need to do.  You can create them in MAX or you can create them programatically.  I would create a scale for each input.  The question you should ask yourself is what kind of flexibility do you need after the app is deployed.  I prefer to store cal info such as offset, span and fullscale units for 4-20 signals in a .INI file and apply it programatically.  I do this for two reasons.  First I dislike having to deal with exporting/importing max configurations.  Second editing a simple text file is an easy way to update/change cal data later on.

Message Edited by Wayne.C on 06-08-2009 11:01 AM

 Another advantage of this is that I can use the cal file to generate a list of sensors that the end user can choose from when running the app.

Message Edited by Wayne.C on 06-08-2009 11:04 AM