Brooks Instrument 5850i - Manual (Page 27)

3-9
Brooks ® Model 5850i
Section 3 Operation
Installation and Operation Manual
X-TMF-5850i-MFC-eng
Part Number: 541B108AAG
December, 2008
and 0% flow indicates the adjustment required of the anticipate
potentiometer. Refer to Figure 3-6.
1. If the flow signal measured on pin 2 decays to -0.05 to -0.5V, then
rises to 0V, the anticipate potentiometer is properly adjusted.
2. If the flow signal decays rapidly and goes below -0.5V before rising to
0 V, the anticipate potentiometer must be adjusted clockwise and
steps a and b repeated.
3. If the flow signal decays slowly and does not go below -0.05 V, the
anticipate potentiometer must be adjusted counterclockwise and
steps a and b repeated.
2. Fast response adjustment (six second response specification guaran-
teed)
Adjustment of the anticipate potentiometer to obtain a flow rate
performance to be within 2% of flow rate commanded in less than six
seconds after setpoint change requires the use of a fast response
flowmeter (500 millisecond response to be within 0.2% of final value or
better) in series with the 5850i and a storage oscilloscope or recorder.
a. Allow the flow controller to stabilize at 0% setpoint for at least thirty
seconds. Make a step in setpoint to the controller from 0-100% of
full scale flow and record the output signal of the fast response
flowmeter.
b. If this signal shows more than 4% overshoot, adjust the anticipate
potentiometer one-half to one turn counterclockwise. If the signal
does not show overshoot but is not within 2% full scale of final value
after six seconds, adjust the anticipate potentiometer one-half to one
turn clockwise. Set command potentiometer for 0% of flow.
c. Repeat steps a and b until the fast response flowmeter output signal
meets the specified response requirements.
NOTE: With the equipment on the previous page (3-9), the anticipate
potentiometer can be adjusted to give optimum response characteristics for
any process.
Figure 3-6 Fast Response Adjustment