Brooks Instrument 5850EM - Manual (Page 48)

3-24
Brooks ® Models 5964, 5850EM
Section 3 Operation Installation and Operation Manual
X-TMF-5964-5850EM-MFC-eng
Part Number: 541B121AHG
November, 2008
c. Repeat Steps a and b above until no further anticipate potentiometer
adjustment is necessary.
d. If the response time and overshoot are not within the required limits, the
response potentiometer must be adjusted to control the amount of
overshoot. Set the command to 0% flow rate (0.000 V) and allow the
flow signal output to stabilize (30 seconds minimum). Step change the
command to 100% (5.000 V) and record the output signal from the fast
response flowmeter.
d1.If this signal shows excessive overshoot above the final value,
adjust the response potentiometer 2 to 3 turns counterclockwise.
d2.If this signal shows that the overshoot above the final value is not
excessive, adjusting the response potentiometer one-half to one turn
clockwise will speed up the response with correspondingly more
overshoot and may also significantly reduce the dead-time between
application of a change in command and the first noticeable change
in flowrate.
e. Repeat Step d above until no further adjustment of the response
potentiometer is necessary. If the desired response characteristics are
still not achieved, some additional improvement can be realized by
making adjustments to the flow control valve. Refer to Section 4-4.
Standard Response and Current I/O PC Board Adjustment #1
(specification not guaranteed)
Note: This procedure requires an oscilloscope, chart recorder or a DVM
with a sample speed of three samples, or greater, per second to monitor
the rate of change of the output signal.
a. Set the command potentiometer for 100% of flow (5.000 V) and wait
about 30 seconds for the flow output signal to stabilize.
b. Step the command signal to zero percent or activate valve override
closed to stop the flow. Observe the flow signal output as it decays.
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 3-14.
c1.If the flow signal decays to -0.05 to -0.5 Volt, then rises to zero Volt,
the anticipate potentiometer is properly adjusted.
c2.If the flow signal decays rapidly and goes below -0.5 Volt before
rising to zero Volt, the anticipate potentiometer must be adjusted
clockwise and Steps a and b repeated.
c3.If the flow signal decays slowly and does not go below -0.5 Volt, the
anticipate potentiometer must be adjusted counterclockwise and
Steps a and b repeated.