Brooks Instrument 5851i - Manual (Page 20)

3-2
Installation and Operation Manual
X-TMF-5851i-MFC-eng
Part Number: 541B109AAG
September, 2009
Brooks ® Model 5851 i
Section 3 Operation
Soft Start enabled by moving a jumper on the PC Board. This circuit
provides a slow injection of the gas as a protection to the process,
particularly those using a volatile or reactive gas. Full gas flow is
achieved in approximately 20 seconds. Refer to Section 2-7.
Precision 5 Volt Reference allows the direct connection of a setpoint
potentiometer to produce a 0-5 Volt command signal to the controller. A
precision ten-turn 2k ohm potentiometer with an integral turns counter
is recommended. This will permit repeatable adjustments of setpoint to
1 part in 1,000.
Valve Override allows full opening and closing of the control valve
independent of the command setting. (Refer to Section 2-6)
3-2 Operating Procedure
a. Apply power to the controller and allow approximately 45 minutes for
the instrument to warm up and stabilize its temperature.
b. Turn on the gas supply.
c. Command 0% flow and observe the controller’s output signal. If the
output is not zero mVdc ±10 mVdc or 4 mAdc ±0.05 mAdc, check
for leaks and if none are found, refer to the re-zeroing procedure in
Sect. 3-3.
d. Set the command for the desired flow rate to assume normal
operation.
Figure 3-1 Flow Sensor Operational Diagram