MKS Mass-Flo 1479A, Instruction Manual, Page: 52 / 72

How To Adjust the Valve Preload Chapter Seven: Troubleshooting
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22. Determine the required valve current limit; add the appropriate headroom from Table 8
to the full scale valve current recorded in step 19. .
Required Valve Current Headroom
MFC Flow Capacity (N2 equivalent) Milliamp Value
≤
50 sccm
24 mA
100 to 500 sccm 18 mA
≥
1000 sccm
12 mA
Table 8: Required Valve Current Headroom
23. Provide a 5 Volt set point signal.
24. Turn off the gas supply.
25. When the flow output has dropped to zero, adjust the Current Limiting potentiometer,
R85, until the required valve current limit is obtained.
Note that counter clockwise rotation increases the maximum current, while clockwise
rotation decreases it.
26. Remove the DMM and reconnect the valve lead.
27. Re-install the brackets and PC assembly and reconnect the valve leads.
28. Reposition the enclosure over the unit and tighten the retaining screws.
29. Re-install the MFC into the process system.