Help with Cole-Parmer MFC instrument control

[Iceman78]

Hi,

I hope someone here can help me.

I am trying to remotely control Cole-Parmer Mass Flow controllers (EW-32907-71 and EW-32907-63 respectively) from my computer.  Each mass flow controller is connected to an NI 4-port RS-232/USB hub via a mini-din to serial cable.  The hub is then connected to the PC via a USB cable.

The PC fails to recognize the MFC when trying to communicate with it.  I have tried Hyperterminal as well as Flow Vision SC and Labview (using Alicat VIs) in an attempt to remotely control the devices.

As per the instruction manual attached, the settings for the serial port are set to:

-19,200 baud

-8 bits

-no parity

-1 stop bit

-no flow control

The settings on the MFC were also set to 19,200 baud.  Both A and @ were tried as IDs on the MFC, but to no sucesss.  While in Hyperterminal, no data is received, and I am unable to provide a setpoint to the MFC in any of the 3 programs.  I have tried skipping the NI hub and connecting one MFC directly to the PC's serial port, but still no success.  I performed a loopback test on the serial ports in Hyperterminal successfully as well.  I even checked the BIOS to ensure the serial ports were active.

How can I get my PC to effectively communicate with the device? 

Any help is greatly appreciated.  Thanks!

[Broken_Arrow]

• Did you perform a loopback test using the DIN cable in the system to verify it is wired correctly?
• Do you have your MFC set for RS232 input (rather than Local or Analog (I think those are the selections).
• Are you sending a carriage return with your command to the MFC? (i.e. the termination character).

[Iceman78]

• I am unsure of how to perform a loopback test on the DIN cable.  It's 8 pins.  Do I connect 3 and 5, 6 and 8, or both? 
• The MFC is indeed set for Serial input.
• I'm unsure as to your last suggestion.  I haven't sent any commands that I know of.  According to the MFC instruction manual, data should appear automatically when opening a connection in Hyperterminal.  If you could give me an example of what I should do here, that'd be great.

[NathanT]

Hello Iceman,

     Have you contacted the manufacturer for help with troubleshooting?  I like your approach of trying to confirm communication in Hyperterminal before moving on to LabVIEW.

Cheers,

NathanT

[Iceman78]

Nathan,

I contacted Cole-Parmer, but unfortunately they really had no new insight to offer me.  I went through every test that I could think of prior to calling them.

And yeah, I don't see the point in beginning work on a new LabVIEW control program if the MFC isn't first recognized by the PC.  If there was a way to check the mini-din to serial cable, I would definitely perform that test. 

[Broken_Arrow]

Hook the 9-pin end into the computer, short out the two pins in the round din that correspond with pins 2 and 3 on the 9-pin. Use Hyperterm to see if you get echos. Make sense?

I would try to send commands anyway. I hooked up a height gauge just last week and the vendor himself told me I don't have to send data to get data, but I did. You never know.

[Iceman78]

There are two RxD's and TxD's though on an 8-pin minidin as opposed to only one of each on the RS-232 9 pin side.  TxD- and RxD- are pins 3 and 5.  TxD+ and RxD+ are pins 6 and 8.  Do I short out both or only one pair?  Also, any tips for doing this?  It's easy to short out the RS-232 port with small alligator clips, but it's impossible to get two of those clips inside of a minidin. 

[Dennis_Knutson]

Where do you see that? Figure 1 does not show that at all.

[Broken_Arrow]

Wait, now I'm confused. It sounds like you have an RS-485 connector there. The 8-pin on that MFC is a proprietary pinout isn't it? Read the manual, the pinout is in there.

[AnalogKid2DigitalMan]

From page 8 in the manual for a single device per port (Adobe image didi not copy properly):

DB-9 Serial Port

5----------Ground--------------------------------------Ground----------8

3----------Transmit------------------------------------Receive---------3

2----------Receive-------------------------------------Transmit--------5

                                                                       8 Pin Mini-DIN Port

Figure 3. Mini-DIN to DB-9 Connection for RS-232 Signals