Can I programmatically change a virtual channel's scaling?

[ChrisCocozzo]

I want to be able to read and write the scaling parameters for a virtual channel. Using NIDAQ 6.8 with MAX 2.0 and LV 6.0.2.

Thanks

[Geneva L.]

This question actually belongs in one of the Measurement Devices categories. In the future, please post to the appropriate forum. You will find similar questions and get exposure to others with similar interests when you post directly into one of those categories.

In answer to your question, you can read the virtual channel properties, but you cannot programmatically change them. If there were a finite number of changes, you could have multiple config files that contained the same virtual channel names. Then, you could programmatically switch which config file MAX was using.

Alternatively, you can apply the scaling in your program if you read the raw value through the virtual channel (no scale) and then pass it into a scaling function.

You can find exa
mples for saving virtual channel properties to a text file and for changing config files in the NI Developer Zone. Start at the http://www.ni.com/support page and choose Example Programs from the Technical Resources pulldown menu. Then, type in keywords, such as "virtual channel" or "change NI-DAQ configuration".

Regards,
Geneva L.
Applications Engineer
National Instruments
http://www.ni.com/support

[rjg]

What do you mean:

"In answer to your question, you can read the virtual channel properties, but you cannot programmatically change them."

MAX can read and write to the DAQ config file, does NI not publish the file spec? or have any sample code? (it doesn't have to be in labview eithor, C/C++ is ok if you have to use it) I have plenty of applications that use internal scaling to allow program control over the calibration process. It would be very nice to store this in the NIDAQ config file, so it can also be viewed, edited and tested through MAX.

Why doesn't ni want to make this available?

[viScience]

Well you could simulate this by programmatically loading one or more new MAX
files.

"rjg" wrote in message
news:5065000000050000008D550000-1007855737000@exchange.ni.com...
> What do you mean:
>
> "In answer to your question, you can read the virtual channel
> properties, but you cannot programmatically change them."
>
> MAX can read and write to the DAQ config file, does NI not publish the
> file spec? or have any sample code? (it doesn't have to be in labview
> eithor, C/C++ is ok if you have to use it) I have plenty of
> applications that use internal scaling to allow program control over
> the calibration process. It would be very nice to store this in the
> NIDAQ config file, so it can also be viewed, edited and tested through
> MA
X.
>
> Why doesn't ni want to make this available?

[rjg]

I know how to programatically load a new MAX file, as examples of that can be found here, but this does me no good, if I don't have a spec or sample code for the file, so that i can write to it with my current calibration settings, and then load it into MAX.