Brooks Instrument 5851EM - Manual (Page 37)

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Brooks ® Models 5965, 5851EM
Section 3 Operation Installation and Operation Manual
X-TMF-5965-5851EM-MFC-eng
Part Number: 541B122AAG
September, 2009
c. The behavior of the flow signal during this transition between 100% and
zero percent flow indicates the adjustment required of the anticipate
potentiometer (refer to Figure 3-7).
1 . lf the flow signal decays to -.05 to -.5 Volt, then rises to zero Volts,
the anticipate potent¡ometer is properly adjusted.
2. lf the flow signal decays rapidly and goes below -.5 Volt before rising
to zero Volt, the anticipate potentiometer must be adjusted clockwise
and Steps a and b repeated.
3. lf the flow signal decays slowly and does not go below -.5 Volt, the
anticipate potentiometer must be adjusted counterclockwise and
Steps a and b repeated.
Response Adjustment #2 (Specification Guaranteed)
Adjustment of the anticipate potentiometer to obtain a flow rate
pedormance to be within 2% of flow rate commanded in less than three
seconds (six seconds for Current l/O Version) after command 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 Model 5965/
5851EM and a storage oscilloscope or recorder.
a. Make a step change in command to the controller from zero to 100% of
full scale flow and record the output signal of the fast response
flowmeter which is in series with the Model 5965/5851EM.
b. lf this signal shows more than 4% overshoot, adjust the anticipate
potentiometer one-half to one turn counterclockwise. lf the signal does
not show overshoot, but is not within 2% full scale of final value after
three seconds (six seconds for Current l/O Version), adjust the
anticipate potentiometer one-half to one turn clockwise. Set the
command potentiometer for zero percent of f low.
c. Repeat Steps a and b until the fast response flowmeter output signal
meets the specified response requirements. Note: With the above
equipment, the anticipate potentiometer can be adjusted to give
optimum response characteristics for any process.