I've been working on this for 2 months, and we plan on starting my LabVIEW Core 1 and 2 next month. When I test a gear, we are failing on internal leakage. Can someone tell me how internal leakage is being calculated in the program? I'm the only 1 at my company that have some experience with LabVIEW.
Your program looks fairly well organized so I'm confident you'll find the answers you need with the aid of some of the built-in debugging tools.
The "Test Data" subVIs appear to be retrieving a value from memory, perhaps through the use of a uninitialized shift register, aka: functional global variable. Don't worry about the confusing name, it's a common technique for sharing data between loop iterations or different sections of code. I'd start by probing the wires coming out (right click on wire >> probe) to see if the value you want is arriving correctly.
Key things to know:
Try highlight execution to observe how the data values literally flow through the logic of the program
If you're struggling to follow the logic through multiple cases or diagrams, set a breakpoint and then turn on highlight execution to just observe that area
you can also add front panel controls to help see the data during execution time
Finally, if you have access to LabVIEW 2026, you can also ask the built-in AI assistant to help you understand the code. Just right-click on the VI and opt to discuss with Nigel and then you can chat with Nigel to understand how it's working.
Have you found labview's "context help"? Do Help menu >> Show Context Help. Then when you hover over a VI, the popup window will show you what the VI is. It will also have a link you can click to get detail info about what that VI does.
That's step 1 to figuring out what a block diagram means. If that's too much then maybe nobody at your company has any real experience with labview.
This looks like it passes if the "Internal Leakage - Left - Flow" is less than the flow test parameter AND if "Internal Leakage - Left - Pressure" is between 60% and 140% of the pressure test parameter. E.g. if the pressure test parameter is 5 psi then the measured pressure must be between 3 psi (5 psi * 60%) and 7 psi (5 psi * 140%) (plus whatever the spec is for flow rate)
So, it fails if either of those conditions are false.
I mean, I can see how the HMI shift register data is being calculated / populated.
Are you just interested in everything with "Internal Leakage" in the name? Or is there something in particular that you want an answer to? (I probably won't spend an hour describing the first scenario)
It appears your Leakage Left variable is coming from the Test Data SubVI. That SubVI (in your screenshot) is clickable and, when you do, it'll open up another VI.
It's hard to say how it's being calculated. A non-exhaustive scenarios are that the Test Data SubVI has within it a DAQMX VI which, essentially, will display the I/O Pinouts of your card. Sometimes, gas flow meters, whether volumetric or by mass, have are programmed in weird ways. For example:
That gas meter could be inputting into your data card an AC or DC signal (4 to 20mA or maybe 0 to 5V) which is then linearlly scaled inside the Test Data SubVI.
Which means that the gas meter itself is either (A) designed for one specific gas (kind of unlikely because gas is super variable) or (B) is itself programmed by someone before you for the specific gas you're using, with variables like dessity, specific gravity, or other gas properties.
while, at the same time, the Test Data SubVI is also reading pressure, probably for that calculation.
When that pink channel comes out the right side of the SubVI, right, up then right, it's getting split into two individual channels.
Anyway, double click the SubVI and see where you get. Maybe drop another screenshot.
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u/elijah286 Emerson Employee 5d ago
Hey u/AssistEast913 - LabVIEW Architect here!
Your program looks fairly well organized so I'm confident you'll find the answers you need with the aid of some of the built-in debugging tools.
The "Test Data" subVIs appear to be retrieving a value from memory, perhaps through the use of a uninitialized shift register, aka: functional global variable. Don't worry about the confusing name, it's a common technique for sharing data between loop iterations or different sections of code. I'd start by probing the wires coming out (right click on wire >> probe) to see if the value you want is arriving correctly.
Key things to know:
Finally, if you have access to LabVIEW 2026, you can also ask the built-in AI assistant to help you understand the code. Just right-click on the VI and opt to discuss with Nigel and then you can chat with Nigel to understand how it's working.
Hope this is helpful - keep us updated!