TRAPPING AND RECORDING AN EVENT

[Tim_56]

Hi,

This is the updated VI. It is still continuously writing to the text file, perhaps I am missing something

Many thanks for your assistance

[paul.r]

Invert the input from the shift register - right click on that input on the compound arithmetic node and select invert input. 

[wiebe@CARYA]

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@paul.r wrote:

Invert the input from the shift register - right click on that input on the compound arithmetic node and select invert input. 

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output that is.

[Tim_56]

Hi,

Tried inverting, but the input into the file is still continuous. Maybe I don't understand as I am completely new to this. Anyway I could send the VI ?

[RTSLVU]

Personally I am not a fan of Feedback Nodes, a Shift Register does the same thing and does not break the data flow paradigm like FB nodes... (IMHO)

Anyway what you need to do here is what we used to call back in the day "Set a flag" 

See my soultion to  How to send email when vacuum reaches threshold for an example.

[wiebe@CARYA]

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@Tim_56 wrote:

Anyway I could send the VI ? 

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Yes, that would help.

[wiebe@CARYA]

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@RTSLVU wrote:

Personally I am not a fan of Feedback Nodes, a Shift Register does the same thing and does not break the data flow paradigm like FB nodes... (IMHO)

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I concur.

[Tim_56]

Hi,

Hopefully I have done this correctly !

[wiebe@CARYA · Accepted solution]

If the output is TRUE, and previous is FALSE, the IO is going up. Then you want to log. So the log should be in the TRUE case of the case structure.

Right click the case, and when showing the FALSE case, select Make this the TRUE case.

Some stuff to reflect on: 

Spoiler

Alternatively, you can invert the output of the compound arithmetic node.

Then you'd have a !Log if !A NAND B, that would read as Don't not log if previous is FALSE and current is TRUE.

That could\should be refactored to A OR !B. That would  read as "don't log if previous is TRUE or current is FALSE".

In general, and AND can be changed to an OR (and vice versa) by inverting ALL inputs and outputs. If you have more then two inverted  terminals, that is usually conceptually easier.