Communication problem with mass flow controller in labview (for NI cDAQ-9174)

[hbateni]

Hi,

we have a mass flow controller (Brooks 5850) that I want to control it by Labview.
We have an NI cDAQ-9174 equiped by NI 9201 (Input module) and NI 9263 (output module).

Based on the Mass flow controller manual there are 3 sets of wire connection: Power supply (+13.5 to +27 V), Setpoint (0(1)-5 Vdc), Flow signal (0(1)-5 Vdc)

The power supply is properly connected and the MFC can power up and I believe the other connection is fine BUT in the labview the Flow Signal is always 1 no matter what is the set point and there is no flow in the system.

Is there anyone who has any information how I can figure out the problem?

Thanks!

[Dennis_Knutson]

Why don't you provide the details on how exactly you have everything connected? A schematic with pin numbers and signal names would be great. And also attach your code/snippet to show how you are doing the write and read.

[hbateni]

Attached is what you asked for. You may find the wire connection on the JPEG file and the code on the vi file.
PS. The solenoid part is controlling the solenoid valve in the system and are working properly and I have to have them in the file if I want to send the gas to specific gas line and not others but you may get ride of that.

Thank you in advance!

[hbateni]

Any idea about my matter? 

[Sam_Sharp]

Have you verified the setpoint voltage coming out of the AO with a multimeter? Is the controller actually controlling, but it's just reading back 1V? (e.g. it's receiving and acting on the input but the output is 0V...either because there's no gas flow or the output is broken).

As the device accepts multiple input types (2xvoltage range inputs, 1 current input and RS485), do you need to first configure it to tell it which input to use (like a remote input setting or a jumper/DIP switch on the device itself)?

[hbateni]

I have checked the setpoint voltage by a multimeter which was the same as the output/setpoint voltage in the labview file.

The controller sends a signal but apparently the MFC doesn't apply the controller order (signal) which means there is no flow rate, so it always reads 1V as a signal for "no flow" condition.

Meanwhile, I have checked the MFC and it doesn't have any problem.

I believe either voltage or current are fine but I used the voltage as the setpoint signal is voltage. So, I assumed manipulating voltage is more convenient.

[Sam_Sharp]

Have you configured the MFC to accept a setpoint voltage? We use bronkhorst MFCs and when we order them we have to specify which input we want to use or we need to connect it to a computer and configure it to use the input voltage as the setpoint - otherwise it might be looking for an RS485 or current setpoint.

As you've verified that the output of the AO is the same as you're writing out, this isn't really a LabVIEW problem and is a problem with your MFC - so I suggest you try taking it up with the device manufacturer.