[Dsg-rtpc] [New Comment] MFC104 seems flaky

[Brian Eng]

Hi Sebastian,

A few comments sections below.

When closing only 100, 102 & 108 I'm not surprised there was still flow as that means the entire length of tubing from the gas pad to the gas panel was "seen" by the MFC so any unequal pressure would cause flow. If you closed all the valves on the gas pad (100, 102 & 104) and still saw flow then it would be more cause for concern.



I'm not sure if pressure systems allows for this, but an easy test would be to install a N2 calibrated rotameter after the MFC with the other side open to atmosphere and adjust the rotameter up/down when flowing and compare that to what the MFC reports back.



Something that can be checked is to verify the gas selected matches what the gas the MFC thinks it should be flowing. On the same computer that the controls are being run from open a web browser and go to http://hb-mfc-bonus-target.jlab.org

If you see a green bar about the gas being changed near the top just refresh the page. If the gas there doesn't match the actual gas flown that would explain the times not matching up.

However, I'd be extremely surprised at this being the problem as this is most likely to manifest itself when changing gases and ending up with something wrong, but not just changing for no reason if someone isn't messing with it.



The only even remotely fishy thing I've seen is that on that on some of the fill cycles the temperature of the MFC dropped more than usual when purging. My guess, the outside temp & gas bottle itself was cold so the cold gas caused the MFC temp to drop more. A few things to keep in mind though: 1) generally a drop in temperature is seen during the purge cycle, though not always as big of a dip nor to that level 2) the temp reading by the MFC is normally only used for calibration so it's readings should be taken with a grain of salt 3) it could just be a red herring and have nothing to do with anything. I only bring it up as food for thought.



I believe there is a MFC available (not sure on the capacity) and hopefully I can remotely walk through the steps with whoever is available to install it on getting the networking setup on one if that ends up being the solution



Again, nothing I've seen in the archived data would lead me to believe anything is wrong with the MFC itself.
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