Hardware suggestions for a gas mass flow controller

[markmakeitso]

Back and forth on 2 fronts today.

Is there an MFC options guide somewhere that could be helpful? Feel like I've wasted a lot of time for both you and our application engineer. Granted it's hopefully worth it if it gets us the most appropriate hardware in the end.

Currently leaning towards mini-DIN with fully populated cables, skip the BB9 and instead using panel mount mini-DIN sockets to break out all wires. Think that maximizes functionality, minimizes add on charges, and isn't too much work on this end. We'll see.

[Kevin_Alicat]

No problem with the time/assistance, we're happy to help and that's what we're here for. If you want for me to have a chat with the application engineer as well, I'd be happy to provide him with what we've covered (or I can forward him this forum discussion for him to review).

This document should cover the majority of what we can do as far as customization options go. Some of the options won't be applicable to you, as they are for different families of devices (such as pressure controller/meter ranges, high flow valve callouts, etc.). There are definitely a lot of options possible, many of which come about when we encounter a customer that needs a specific feature we don't yet have. They are split between physical part modifications and software modifications (top and bottom half of the sheet).

The document was intended for decoding an existing part number, and provides no info on what options are mutually exclusive. The first two chunks of the part number are what state the type and range, and are therefore not optional elements. The valve options are similarly dependent on your setup and should be sized per your application by the application engineer. The main ones you would want to look at are the display options (I don't recommend removing the display, as it provides a decent troubleshooting ability), the communication options (DeviceNET, Ethernet/IP, Modbus, and Profibus are not supported in LabVIEW through our driver library, but I have had good success with a free Modbus driver package from the NI forums to interface with Modbus 232/485 and I believe there are purchasable options for ethernet/IP and DeviceNET through NI, but I would recommend either of those only if you are already set up for one of those protocols).

As for the "adder codes" (essentially additional option codes), many of them are callouts for presetting user configurable options or for the device to be checked to higher accuracy tolerances, but the main ones you might have use for would be the totalizer which is useful for providing info on total volume used over a period of time (though you can approximate this if you have a logging functionality by means of a numeric integration routine, the Alicat does this internally with a 1 ms time resolution).

As long as the cables aren't going to be tugged or jostled loose, the 8 pin version should do fine as you want to use the full digital and analog outputs. If purchasing them from us, go with the default double-ended cables and not the ones that end in "RS" which are made more flexible for use with RS-232/485 as they only have RX, Tx, and GND present.

[markmakeitso]

Hi Kevin,

Just a little heads up on progress. I received the first MFC, got it powered up successfully and then snagged an elabguy breakout PCB for the 8 pin mini DIN, which worked out well once I remembered the wonky pin numbering. Related to that, the generic cables I ordered turned out to have swapped pairs of wires, so that was a little bit more headache. It appears unless the cable description very specifically says "straight through" they're probably a crossover style. Cables labeled "Apple compatible" or "serial DIN" are also likely to cause headaches. Quality time with a multimeter and a loopback test from the far end of the cable finally got me sending successful commands with your V1.04 serial. A VISA utility VI that I had on hand also works adequately with some minor tweaks. So, commanding gas selections and setpoints just fine now, and briefly tried setpoints via analog voltage too. Next steps are to program MFC response processing, continue on my state machine framework, and order up the rest of our MFCs, hopefully soon. 

Have fun over there,

Mark

[Kevin_Alicat]

Hi Mark,

Thanks for the update. Cabling/wiring issues can be a pain to track down sometimes, but I am glad you have the device communicating now. Feel free to let me know if you come across any issues or questions, and I will be happy to assist.

Cheers,

[markmakeitso]

Hi Kevin,

Had a meeting today, and we're shaping up to order the rest of the MFCs. We're mapping out the physical installation, and had a couple questions.

-We'd like to use 1/4" Swagelok as much as possible, to match our current inventory. Could we use adapter fittings on either side of MFCs that have NPT threads to get to Swagelok, and then just keep the fittings in place for calibrations at your place?

-If we used a filter at each MFC inlet would they preferably stay with the system, or could they be disconnected along with the MFC when sent in for calibration?

Thanks,
Mark

[Kevin_Alicat]

Hi Mark,

Glad to hear the progress update.

-For the fittings, using a Swagelok to NPT adapter should work for calibrations but you would likely have to tell the customer service representative that you'd like the adapters left on. I believe it is standard procedure to remove all fittings, but they stated that if instructed they could work around that (it is primarily so that fittings/accessories do not get lost if sent back with the device, such as if the flow body was damaged in the field and needs replacement, at which point the device would be disassembled). Another option would be to specify a device with 1/4" Swagelok VCR/VCO/Compression fittings when ordered - this would result in a device that has the desired Swagelok fitting welded onto a plate and bolted over the NPT threaded ports (sealing by means of an O-ring face seal). There's a small price addition for this, and main benefit would be that the device would be leak-checked with the fittings in place when assembled or repaired.

-For the filtration, our service department would likely prefer that the filters remain with the system and not on the devices. This is only for the reason above: that there's a small risk of losing the fittings/filters/accessories either in transportation (if loose accessories are sent) or during the repair/calibration process (the devices can change hands a few times, depending on the work required). Similar to the statement on the fittings, if you have a filter that you would like left in during the leak-checking and calibration steps, please let them know when setting the order up and they will do their best to comply (where possible).

As always, feel free to let me know if you have any questions or concerns and I will be happy to assist.

[markmakeitso]

Hi Kevin,

Fairly quick question this time. Is it worth not powering up an MFC if it will not be used during a multiple-hour process? 1 of our MFCs will likely only be used by itself, and the other 4 will likely be used in matched pairs 99% of the time. Any detriment to them being powered on for several hours (with supply and output side isolation solenoids closed) without gas flow or commands? Any effect on calibration or hardware longevity?

We currently have 16 relay channels and there are a few extra, but splitting to all 5 would likely require another relay board.

Thanks,

Mark

[Kevin_Alicat]

Hi Mark,

As long as the valve is kept closed (usually by keeping the MFC with a zero setpoint), there are no issues with having it powered for prolonged periods with no flow. We have some customers that have these devices powered pretty much 24/7.

Prolonged power with no flow is only a concern if it the valve is open (non-zerosetpoint on MFC's) and gets overheated by being at full current draw, but even then low flow devices (MC series) would likely just artificially increase the temperature of the sensors producing a temporarily incorrect flow reading once gas is actually flowing. The temperature will take a bit to dissipate and during this time it will think that the temperature reading is higher than the gas temperature actually is. The larger valves (MCR series with large electromagnets) can potentially get hot enough to cause damage to the valve control circuitry (located on the valve). 

Cheers!

[markmakeitso]

Excellent, thanks for the answer and explanation. Sounds like we're safe with powering them all together. Maybe if I'm feeling frisky towards the end of the project we could separate into something more complicated.