sbRio analog input scaling

[erfigge]

I have an sbRio 9612 and I'm building an application that takes analog inputs (0 - 10 vdc) and scales them to an engineering unit like psi for example.  I know how to do the scaling directly on the properties of the analog input, but I was wondering if it is possible to get to those properties in the realtime?  Basically the inputs should be calibrated every 6 months, and if I want to calibrate the entire system from the sensor to the actual input then I need a way to adjust the scaling or calibration of the input in the labview realtime. 

Here is the example process.

1) Put a known pressure on the pressure sensor, for this example 10 psi.  The pressure sensor generates a voltage that goes into AI0 and that scales it to 10.1 psi, so I want to be able to calibrate it back to 10 psi. 

Any built in methods to do this?

[Jeff-P]

Hi,

it sounds like what you are trying to do can be done in your RT controller using read/write controls on the FPGA interface palette. That will let you update the values on the FPGA from your RT controller to tune your input scaling.

Regards,

[erfigge]

Well, I'm actually not using the FPGA, I'm using the scan interface on the RT controller.  I have found a few things but none that let me adjust the scaling or calibration factors.

[Jeff-P]

So are you trying to change the scaling variables on your RT controller from your host PC?

[erfigge]

Yes, in some way or form.  We currently interact with an aftermarket io setup and I pass calibration values to it via network variables.  I would like to do the same sort of thing now with the actual NI io.

[viScience]

It is unfortunate that there is not a direct way to programatically modify the scaling factors on a RIO scan engine IOV.  This information is defined in the project and deployed to the target encoded into a file called variables.xml.  It is possible to decode this XML file, modify the scaling factor, replace the original file and then reboot.  I have mentioned this in a LabVIEW RT idea post but never got any traction.  It seems fundamental that if you offer scaling configuration in the project you should be able to programmatically modify it in a built application.

[erfigge]

I would agree, that is a pretty big oversight.  Do you have any suggestions on easy ways to be able to calibrate io's?  Can you do something like that with FPGA?  I haven't really needed to use the FPGA to this point and if I don't have to I don't want to, but if this can be done in the FPGA then that would be a pretty compelling reason to make that switch.

[viScience]

Maybe this would help.... http://zone.ni.com/devzone/cda/epd/p/id/6206