Can't read my results from VI

[RoryOBrien85]

Hi guys,

I'm running a wind tunnel experiment using Labview 8.2. I've inherited the VI from a previous year, which i didn't create. The experiment is using a potentiometer with a 5 volt analog input through a DAQCard-6024E. I've attached the VI...

There are no errors in the VI but when i run it, i'm meant to be getting a reading on the graphs on the front panel (because of the potentiometer and supply voltage). I'm a complete novice at Labview, and i only need to run this VI to finish my experiment. Any help you guys could give me would really be appreciated...

Thanks.

[RavensFan]

Nothing jumps out at me as to why your indicators would not be showing results.  I would recommend putting probes on the various wires, even turn on execution highlighting.  See what data is flowing down the wires.

[RoryOBrien85]

Could it be something to do with the file thing down at the bottom of the right hand corner in the block diagram? It's missing... Is it easy to create a new one?

Thanks...

[altenbach]

There are a couple of things that I don't understand.

Most of the time you analyze blank data and nothing should show at all. Only if the "trigger and gate" express VI shows "data available=true", the graph should update AND the VI will stop at the same time. Thus you should never see anything on the graphs until the VI stops. Does it ever trigger? Hook up a chart or graph after the filter, but before the trigger to see the raw data at all times.

What determines the loop rate?

You AO update needs to be done only once before the loop starts and not over and over again inside the loop. The voltage never changes!

[RoryOBrien85]

Thanks for the reply...

No, i don't see any readings at all when i run it... To be honest, i'm a complete novice at Labview and don't understand some of the terms you're using in your post. Will i have to create a file like the one in the right hand (original is missing) corner of the block diagram for the VI to run? I haven't a clue what's going on, so any help you could give me will be appreciated...

Thanks.

[altenbach]

Well, it's either hardware or software. 🙂

Is everything hooked up correctly to the DAQ card? Can you hook up a voltmeter to see if you get 5V on the AO?

What happens when you run it? Do e.g. the "Sensor Angle (degrees)" and "Pitch Angle (degrees)" get updated at least?

Your AI takes ~3 seconds with the current settings and this probably determines the loop rate. Have you tried running the VI with execution highlighting (press the "light-bulb" button and run it while watching the diagram. Is anything moving or do you have a permanent green arrow on e.g. the AI subVI?

Sorry, we cannot test because we don't have your hardware.

[RoryOBrien85]

I've hooked up a voltmeter, and everything works fine with the potentiometer and DAQCard, so it's not a problem with the hardware...

Yeah, i've ran it with the lightbulb thing on in the block diagram. Everything works fine up to the point where it reaches that area in the bottom right hand corner. When it hits that, the reading cnahnges from "true" to "false".

Message Edited by RoryOBrien85 on 03-10-2008 04:57 AM

[RoryOBrien85]

Hi,

You also mentioned in your previous post, that i should "hook up a chart or graph after the filter, but before the trigger to see the raw data at all times"... How do you do this?

Thanks...

[altenbach]

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RoryOBrien85 wrote:

Yeah, i've ran it with the lightbulb thing on in the block diagram. Everything works fine up to the point where it reaches that area in the bottom right hand corner. When it hits that, the reading cnahnges from "true" to "false".

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What is "it"? Do you mean the boolean wire going to the case structure?

What happens when it reaches that area? (program crash, stall, nothing, ...) How does it change from true to false? The report VIs in the case structure have error terminals. Create an indicator for them to see if they want to tell you something.

Instead of creating a new graph before the trigger, just right-click the wire and select "probe". You should get a small window that shows details of the data in the wire while running the VI.