Pressure sensors

[Natig]

Hi, everyone. 

I have a code to read pressure sensors and present it in a graph. 

When I start it goes very slowly as in picture PRESSURE 4. I wan to see a realtime data like in a normal seconds. 

I am new to labview and do not really understand what can go wrong in this code. 

I would really appreciate any help.

[GerdW]

Hi Natig,

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@Natig wrote:

I am new to labview and do not really understand what can go wrong in this code. 

I would really appreciate any help.

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When you are new to LabVIEW then you should take some beginner tutorials. There are some offer at the top of the LabVIEW board!

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@Natig wrote:

When I start it goes very slowly as in picture PRESSURE 4. I wan to see a realtime data like in a normal seconds. 

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You set both task to read 1001 samples at 10kS/s, so the reading will need 0.1001 s. This will limit the iteration rate to ~10Hz.

Additionally you placed a 500ms wait inside your loop, so it will iterate with just 2Hz.

What do you understand as "realtime"? We mostly understand you want to use a cRIO device instead of your Windows computer + ULx hardware…

Suggestions:

• Set the number of samples to read to 200. This will give an update rate of 50Hz.
• Remove the wait from your loop, so the DAQ device will determine the loop rate…

[Natig]

Hi, with realtime I mean I want to see what is in sensor  in the graph during an experiment. 

I changed samples to read and removed wait function. I think some other problems because lines do not change with time. Once I pres run I see lines in graph but then they do not change as time goes on. Just like in the picture 7. 

[GerdW]

Hi Natig,

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@Natig wrote:

I think some other problems because lines do not change with time.

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Are there any errors in the loop?

You don't check them in your VI…

[Natig]

No I do not get any errors, I added new error handlers as well, but there no error. 

[GerdW]

Hi Natig,

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@Natig wrote:

No I do not get any errors, I added new error handlers as well, but there no error. 

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So the problem could be in the wiring of your sensors to the DAQ device…

Did you check the wiring? Can you read the expected data using a simple DMM?

[LVNinja]

Let's go back a few steps. 

Try reading just one channel first, with no filtering, until you get the quick response you're looking for. 

Once you have it going, then add the second  channel. I believe you can read the two channels, with just one function,  not sure if this how it goes, but something like this: 

Using physical channel like Dev0/Ai0-Ai1 and then change the function 

[Natig]

I deleted mixed graph and used waveform chart instead it worked. 

But now I have a new problem, Although I have two channel only one the their value is right in the graph, second one is represented with minimum value (-10 in create channel vi). You can see it from pictures. For channel 1 i expect 6.8 and for channel 2 I expect 1,9.

I have litteraly copied the same code in order to be able to see 2 different channels. But it seems one of them is not working. I am using ULx library not DAQ.

And one more problem is X axes in graph which shows 9 digits number, I have unchecked autoscale and tried to change startin and ending point manually but it returns to that 9 digits number instantly, I need to see seconds there

[Natig]

With only one channel, I got the response I wanted (without filter graph is too noisy). 

I am using ULx library not DAQ, it is possible to change functions in read function to 2 d DBL, but I couldnt find how to change physical channel to Dev0/Ai0-Ai1. There was no option like this, only single channels was possible. 

[GerdW]

Hi Natig,

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@Natig wrote:

With only one channel, I got the response I wanted (without filter graph is too noisy). 

I am using ULx library not DAQ, it is possible to change functions in read function to 2 d DBL, but I couldnt find how to change physical channel to Dev0/Ai0-Ai1. There was no option like this, only single channels was possible. 

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With DAQmx you use the channel constant/control and select the channels as "ai0:1" (to select any channels from ai0 to ai1). I guess ULx handles this very similar…

You only need ONE task that reads 2 channels with "N samples"!