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Coupling loops, timer and duty cycle problem


Hello all,


I am since a week working with LabVIEW, so I am pretty new. I want to make a test rig to test the regeneration of the compressor. The test procedure is described by the manufacturer of the compressor and I want to do the same test.


To do this I bought the following:


  • cDAQ-9174, CompactDAQ chassis (4 slot USB)cDAQ-9174
  • NI 9215 4 ch, 16-Bit, +/-10 V, 100 kS/s/ch, SS Diff AI
  • NI 9481 4-Ch 30 V, 60 V, 250 VAC EM Form A SPST Relay
  • USB-232 1-port USB to RS232 Serial Interface, 2m
  • LabVIEW Base Development System, Windows, English


So basically I have everything to make this test rig working. The pneumatic and electric scheme of the test rig you can see in the attachment. The test procedure is pretty simple, see this below.


  • Fill the 3.7 liter reservoir to 5 bar by means of the compressor
  • Fill the 3.7 liter reservoir from 5 till 10 bar by means of the compressor
  • Exhaust the 3.7 liter reservoir via the outlet solenoid valve from 10 till 5 bar
  • Repeat steps 2 and 3 until 50 hours compressor run time is reached


  • The compressor duty cycle is 10 %. The period time is 10 minutes, so the running time will be 1 minute.


I expect to have the product that I have bought in a day of 5/6, so I can’t work with it now. But when I have the products I want to test as soon as possible. So at the moment I am trying to make a program that controls my test rig. Instead of the measured signals, I now have used a pointer slide.


Because I didn’t follow a training (jet) by National Instruments it’s very difficult to make a working program. Before I even got started with making something in LabVIEW I have made a flowchart to know how I want to have my program working. This flowchart can be seen in the attachment.


What my problem is, I don’t know how to make this program in LabVIEW. At the moment I have the flow scheme divided in several pieces. I don’t know if this is correct, but I must start somewhere. In the flow scheme you can see what steps belongs to what piece.


I have attached the three pieces. I think that the first two pieces are correct. The third piece I don’t understand how to make this work. I have some problems with this. I have tried something to activate the compressor with a duty cycle (not 10% just used something). I didn’t implement this to my third part, because I don’t know how to make this. The problem is, I don’t know how to make the loop to fill and exhaust the reservoir. Also the time counter doesn’t work jet the way I want it to work. It now counts the simulation time and not the time that the compressor (d-out-2) is activated.


Even if I can make this, I don’t know how to couple the separate pieces to make it one program. Can anyone please help me? Thanks in advance!

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Rest of my vi's

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I have been busy with the problems and I have tried now the flat sequence structure. But I think I cannot use this structure.


First I want to solve the problem of the coupling of loops. As you can read in my previous post, I am going to use the signal of the pressure sensor. Now I used some pointer slides to represent the air pressure, but I must use only one pointer slider. Now I cannot do that, because some loops will become active again. What I need now is when a loop is finished, the next one must start and the other one cannot become active again. Does anybody know how to make this?


For my currenct model you can see the attachment.



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Thanks for your posting on this forum. I think that you can use the attachments to go further, but I recommend to take a LabVIEW course (  

I hope this helps and if you have any other question don't hesitate to ask.




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