[Dsg-mvt] [New Logentry] C4H10 mfc issues

[mcmullen at jlab.org]

Logentry Text:
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The mixing system mass flow controllers for isobutane continue to exhibit odd behavior. This morning, the solve seemed to be to set the mix flow much higher (~250 for Ar, 25for C4H10, 0 CF4 is not hook up). The isobutane seem to be responsive but slow to settle at the set point. We (Maxime, Franke, and I) that setting the flow high would allow the tanks to fill. They system would still need to be in Automode, to engage the software pressure controls. 

The one standout issue was the flow readout of Mix 2 isobutane, which was ~35sccm, even with the mfc valve closed. I attempted to zero the mfc's readback, but this seemed to make it worse. After zeroing with the manual valves for both Ar, and C4H10 as well as the Mix 2 tank closed. The readback with the mfc valve closed was a high as 364sccm. The flow rates tend to drop (very slowly) towards the set point, but does not necessarily reach that point. 

We should swap in the spare at some point soon to see if the behavior is the same. I will inform the MVT staff to use the premix for now. 

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/3500901
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