re-read in values in measurement file when file is updated

[eugeniap]

Hi,

I'm trying to control a power supply with labview and set the voltage. I've currently got it working reading in a measurement file and setting it to the value within the file. I'm now having the issue that I would like to update this value when the file is changed, as in read the file again when it is updated and set the new voltage. I've tried several things but if I put the file within the while loop then it reads it once and then returns 0 following the first loop. Outside the while loop it only reads the initial value.

I'm quite new to labview so any help would be much appreciated.

Thanks,

E

[crossrulz]

You might want to explain your application a little better.  Looking for a file to change to set an instrument does not seem like a good idea.  Who is changing the file?  How often is the file changed?

A better way might be to use a queue or notifier for setting the instrument.

[eugeniap]

The file will be eventually setting many things, but this is just an initial program to get used to the ideas. The power supply is initialised first and then the program literally uses 'Read From Measurement File' which contains a single value of the voltage to set the voltage. The file is changed by a person, and not at a set time interval it's merely so that you can run the program get some data and then change the settings if you wish. There are voltage limits in place so it's quite safe etc.

This method has been used alot for this, so it's definitely not an issue. I just was hoping to find out how to update a read in value when the file is changed.

Thanks,

E

[MStewart · Accepted solution]

You can use the File/Directory Info VI to get the time that the file was last modified.  If the time has changed, read new values.

[eugeniap]

Hi,

Thanks for the help - would it be possible for you to save your VI so I can open it in Labview 2011 please? I'll try and use the File/Director info VI now but would be great to be able to see the example in use.

Many thanks, E

[MStewart]

Here is the 2011 version

[eugeniap]

That's great thanks for the help 🙂