Brooks connection using usb 6229

[TejasPatel]

Thanks in advance.

[Dennis_Knutson]

Thanks for what? You haven't asked a question.

[TejasPatel]

I m very new user of Labview. I want to control three Bronkhorst MFC for my gases flow controls. I made one programm with the help of old working programm.

I have attached that programm for your reference. It is not working properly. It is not getting mfc ON or any reading. How can i make it OK?

I am using USB6229 for this operation.

Give me reply.

[M0535]

Hi TejasPatel,

Would you be able to upload the older, working program your new one is based off of?

It should narrow down what might need to be added or changed to get the new program working.

[Kaleb_A]

Hello TejasPatel,

What troubleshooting have you tried? You can use probes and highlight execution to see what is happening with your data. http://www.ni.com/getting-started/labview-basics/debug 

[chembo]

Set points: I assume the MFCs are analog. The DAQ task contolling the set points (DAQ Assistant 2) uses scales. I cannot see them, but just make sure that the voltage output is 0 to 5 Volt. Usually this is the set point range of analog MFCs.

Right now the conditional terminal of the while loop is set to 'Continue if TRUE' and the STOP button is set to 'Latch when pressed', so it doesn't matter what you do, this loop will run just one time. I other words, you can send just a single set point to the MFCs.

Flow readback: This is also just one time shot, and it is even possible that you try to read the flow before the set point was send to the MFC. Also, the MFCs have usually arround one second settling time. You may try to wait a little bit after the set point is active, before you read the flow.

You need to put the write/read DAQ calls in a loop in order to control the devices continuously, i.e. change set points and monitor the flow readback.

[TejasPatel]

Good morning and thank you very much for your reply. I am forwarding herewith my old / base programm. From this - Now I donot want to use mfc4 n 5 and any temp. controls. I also donot want to see the graph OR any data record or so.

Just I want to see the flow from MFC1,2,3. ONLY.

Thank you for your time.

[chembo · Accepted solution]

I updated your VI. I never used DAQmx Express VIs, but hopefully it will work. Please note that the AI channel reading mode was changed to 1 sample (on demand).

I cannot check your Custom Scaling. If you don't see the expected flow, check the custom scales in the DAQmx  express VI properties. If the scale definitions are missing, just pick <No Scale> for the input and output and signal range 0 to 5 volt, or whatever your MFC requires.

[TejasPatel]

Thank you very much dear friend. It is working. Just one thing, i want to bring your attention that any one MFC which i am not using for feeding. i.e. Zero Input than still in the output display panel it is showing some -ve values from -10.2 to -20.45 or so on. How can I eliminate this OR how can i keep nonworking mfc completer ZERO...Close....

Hav a lovely day..

[chembo]

I don't think this problem is LabVIEW related.

There is always some readback from an analog MFC at zero set point, but this is usually under 1% of full scale. You have flow of  -10 to -20 on a full scale range of 100 which means an error of -10% to -20%. This is to high for any MFC.

You may try to zero the MFC, if possible (read the manufacturers zeroing procedure), and check the wiring.