Brooks Instrument 5851EM - Manual (Page 29)

3-3
Brooks ® Models 5965, 5851EM
Section 3 Operation Installation and Operation Manual
X-TMF-5965-5851EM-MFC-eng
Part Number: 541B122AAG
September, 2009
d. Set the command for the desired flow rate to assume normal operation.
Note: lf a separate positive shut-off solenoid valve is not installed, a
flow signal may result from leak-through. Leak-through is more
significant with stainless steel and Teflon valve seats.
3-3 Zero Adjustment
Each Model 5965/5851EM is factory adjusted to provide azero +10 mVdc
signal (or a 4 mAdc +.05 mAdc signal, Current l/O Version) at zero flow.
After initial installation and warm-up in the gas system, the zero flow
indication may be other than the factory setting. This is primarily caused by
changes in temperature between our calibration laboratory and the final
installation. The zero flow reading can also be affected, to a small degree,
by changes in line pressure and mounting attitude.
To check zero in an unpressurized line, always mount the controller in its
final configuration and allow a minimum of twenty minutes for the
temperature of the controller and its environment to stabilize. using a
suitable voltmeter, check the controller output signal. lf it differs from the
factory setting, adjust it by removing the lower pot hole plug which is
located closest to the controller body. Adjust the zero potentiometer (refer
to Figure 3-6) until the desired output signal is obtained.
3-4 Calibration Procedure
Note 1: lf the valve has been disassembled and any of the following parts
have been replaced, the device must be returned to Brooks Instrument for
control valve adjustment before the Model 5965/5851EM may be
calibrated.
• orifice • lower guide spring
• valve stem • valve seat
• plunger • gland nut
• plunger extension
Note 2: calibration of the Model 5965/5851EM mass flow controller
requires the use of a DigitalVoltmeter (DVM) and a precision flow standard
calibrator such as the Brooks lnstrument’s Vol-U-Meter
® . lt is
recommended that the calibration be performed only by trained and
qualified service personnel.
Note 3: lf the mass flow controller is to be used on a gas other than the
calibration gas, apply the appropriate sensor conversion factor (refer to
section 4-4). size the orifice for actual operating conditions (refer to
Section 4-5).