Mass flow controller Labview project not working

[LieBerry]

Good evening everyone,

I'm writing this post after hours of troubleshooting and really require some help. I am working on a collegiate project creating a LabView program for a MKS mass flow controller.

I have so far created a program that controls the set point, the flow scale, and a drop down for the necessary gasses.

I bought a NI USB 6001 and a RS232 cable to bare wire, to both send a 0-5v signal to generate the set point and to read a 0-5v signal from the flow signal output.

However, after attempting to test the program in our college lab, I can't seem to get the MFC to activate at all, it doesn't seem to pushing out any gas. I am not sure if its due to the LabView Code or the wiring.

I am connecting the pins of the rs232 cable db 15 to barewire to the NI USB 6001 as follows:

pin 2 - AI 0 of NI USB 6001 ( Flow signal Output) (Final plan is to connect to a breadboard and run across a 10k ohm resistor and then connect to AI 0, but as of now just trying to obtain a signal)

pin 4 - Connected to the constant 5v digital output of the NI USB 6001 (MFC Valve open) (This I'm skeptical if it works since the NI USB 6001 is busy generating and reading signals, I have no idea if this digital output continues to generate 5v. In addition, I'm not sure that 5v is enough to open the valve since the range is 5v to 15v)

pin 7 - Positive terminal of power supply (A power supply is needed to power the MFC since it takes 15v to 24v)

pin 8 - AO 0 of NI USB 6001 (Setpoint Input)

pin 15 - negative terminal of power supply (MFC Chassis ground, i'm not sure if this is the correct ground to use)

I apologize if these are dumb questions as I am a beginner to LabView and have had no other experience utilizing the program besides this project. Below I have attached my VI and a picture of the MFC pin out from the manual.

[Bob_Schor]

Don't fret about being a beginner -- we all were, at one point!

Thank you for attaching a VI, and thank you for using LabVIEW 2021 (and not something more recent, as many of us are using older versions and have not downloaded the "latest" ...).  I hope you are developing your code "inside" a LabVIEW Project (and, I hope, all of the "software pieces", like TypeDefs and sub-VIs, are included in a (physical, on-disk) folder along with the Project file (.lvproj).  If that is the case, please do the following:

• Open File Explorer.
• Find the Project Folder.
• Right-click the folder, choose "Send to", "Compressed (zipped) folder".
• Attach the resulting .zip file.

This will let us see "all the pieces" of your project.

Then we can make suggestions ...

• Almost always use the Error Line to "serialize" your code.
• Almost never use a Frame Sequence (see the previous Bullet Point).
• Try to keep your wires running horizontally and "unkinked".
• Use sub-VIs to "hide the messy details".  Make a simple Icon that says what the sub-VI does (like 3 short words of text).
• Try to get all your VIs to fit on a single Laptop screen -- really helps user/viewer "see the big picture".

I assume you know the Three Laws of Data Flow, right?

1. A structure doesn't start until all of its inputs have data present.
2. Data doesn't flow out of a structure until the structure exits.
3. If two elements have no "wire" from output of one to input of the other, you can't tell which executes first.

The Third Law is what makes LabVIEW so powerful, and encourages parallel processing.  There's also a "zero-th" Law, "Data flows (mostly) in Wires".  (I'm not sure that's an "official" rule -- I just made that up ...).

Bob Schor

[LVNinja]

Hi LieBerry

You need to troubleshoot to know if the problem is on the signal from /to flow controller or from the USB 60001. 

Before using the USB 6001, try troubleshooting with a multimeter and see if you can make it activate with simple electrical signals, use a 5V power supply to emulate the Digital IO from USB 6001 to activate the valve.

Check how much current you need on these signals (PIn 4 of DB14) and see if the USB will be able to provide that current. if not, you will need o add something in between USB 6001 and the Mass controller to be able to handle the current( like a relay).

Once you are confident that the mass controller works as desired, then turn to USB 6001 and see if it will follow your program (with a multimeter to measure the AO and the digital IO). 

I hope you are able to isolate the problem.