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Chapter Six: Embedded Web-Based GUI and Diagnostics Tuning the MFC for Optional PC
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The proportional control setting (Kp) has a minimum value of zero but no maximum value. The factory-
shipped setting is for a typical mass flow control system with Nitrogen as the process gas. The actual value
depends on the configuration of the

FC. See the
Adjusting the Proportional and Integral Control
section for
an explanation of how to set the proportional control setting (Kp) using the embedded Ethernet UI.
Integral Term (Ki)
The action of the Integral (I) term creates a valve drive signal that is proportional to the magnitude and sign of
the area under the error signal curve (error signal with respect to time). Therefore, as time passes, the integral
term acts to position the valve to reduce the error signal to zero. A decrease in the integral control setting (Ki)
increases the period of time over which the error signal is generated, and the system response gets slower. The
following figure
shows the effects of the Integral term.
Figure 30: Effects of the Integral Control
The proportional control setting (Ki) has a minimum value of zero but no maximum value. The factory-
shipped setting is for a typical mass flow control system with Nitrogen as the process gas. The actual value
depends on the configuration of the MFC. See the
Adjusting the Proportional and Integral Control
section on
page 75 for an explanation of how to set the integral control setting (Ki) using the embedded Ethernet UI.
Optional Command Min Offset
The value of the Command Min Offset affects the MFC’s initial response to setpoint from a valve closed
position. The value biases the MFC’s control valve relative to its mechanical preload. When set to zero “0”,
the valve must overcome the total mechanical preload of the MFC prior to opening and allowing flow.
Increasing the Command Min Offset reduces the valve preload which can reduce “dead-time”. The
Command Min Offset will also affect the response time and overshoot. Generally the value will be in the 0 to
25 range although higher values are allowed. Note if the value is set too large, the closed conductance
leakage through the valve will increase.