06-19-2009 12:47 PM
I have been using the alicat mass flow controller and I'm wondering if there is a better idea than mine for controlling these with labview.
The attached is a simple control program that I made and the four controllers can be accessed sequentially by sequence structure in the while loop.
The problem is that it takes about 4 or 5 seconds to read from and write to controllers for one loop.
Is there any better way to do reading and writing faster than that? I'm using LV 8.2 and the four controller are plugged into BB9 and BB9 is connected to
the computer through the USB-serieal cable.
Any idea would be appreciated.
Thank you very much.
06-22-2009 11:14 AM
Is there any reason you need these to run sequentially? Assuming you have a different VISA Resource name for each controller, you could remove the sequence structure and have each subvi run in parallel. I'm not sure how the BB9 shows up in MAX though.
06-22-2009 08:08 PM
Thank you for your reply.
I ran sequentially because the mass flow controllers share the same serial port (COM8) and it is not possible that I can sample and wirte the data to the four controllers at the same time.
Could you give me some advice on that?
And also how can I run each subVi in parallel? You mean four different while loop?
I appreciate your help.
06-23-2009 11:11 AM
If everything is going through one COM port, then running your subVIs in parallel won't work. One thing you may want to try is timing each sequence in your flat sequence structure to see if any of the mass flow controllers is taking longer than the others. You can use the Tick Count (ms) function at the beginning of your sequence, and once for every additional sequence. Subtract these values (new tick count - old tick count) to get an idea of how long each sequence is taking.
07-10-2009 04:17 PM - last edited on 07-14-2009 11:35 AM by Support
July 10, 2009
I did not see this post till now.. And.. If you do not have a solution yet then perhaps I can help. I use the Flow Meters here: http://www.massflowmetersandcontrollers.com/ and I use the 0-5 VDC output and can read at very high speeds. I also use LabVIEW 6.1 because it is not as "hoggy" as the 8X versions.... I can make an executable much faster and it is not so doggone huge...
I am going on vacation to Mexico so if you need something pop me an e-mail at the URL I gave you above. The e-mail is at the very bottom..
Also, Sierra MCF's are calibrated on primary standards... Not like the Alicat AND the Sierra is a REAL MFC, not a pressure transducer based MFC. In short the low cost MFC's shown in the link use the same "engine" as the more costly $3000 units!
Thanks a million!
10-06-2009 08:25 AM
Hi everyone, I am also using alicat MFC and successfully talk to and send set point to it using hyperterminal. However, I failed to use labview to do the same thing, with the earlist error occurs at the "VISA configure serial port (Instr).vi" where it gives the error code "Property Node (arg 1) in VISA Configure Serial Port (Instr).vi".
Very upsetting. Does anyone have similar experiences or any idea about how to fix this?
10-07-2009 12:10 PM
If you try to configure your serial port for settings that it cannot handle, you will throw an error. Also, if you have hyperterminal still open to your COM port, you will not be able to open another reference to the port. Hope this helps!
10-08-2009 04:34 AM
I located the error source, which is stupidly simple. The USB-serial adapter I was using seems to be incompatible with labview. What I did was just use a high-profile adapter and it works.
To be honest I really hate this type of error, which can waste one a lot of time and effort to locate.