Brooks Instrument 5851E - Manual (Page 26)

3-6
Brooks ® Model 5851E
Section 3 Operation Installation and Operation Manual
X-TMF-5851E-MFC-eng
Part Number: 541B104AAG
November, 2008
To check zero always mount the controller in its final configuration and
allow a minimum of 20 minutes for the temperature of the controller and its
environment to stabilize. Using a suitable voltmeter check the controller
output signal. If it differs from the factory setting adjust it by removing the
lower pot hold 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: If the valve has been disassembled and any of the following parts
have been replaced the control valve adjusting procedure in Section 4-4C
must be performed before the Model 5851E is calibrated.
orifice
valve stem
plunger
lower guide spring
valve seat
Note 2: Calibration of the Model 5851E mass flow controller requires the
use of a digital voltmeter (DVM) and a precision flow standard calibrator
such as the Brooks Vol-U-Meter
® . It is recommended that the calibration be
performed only by trained and qualified service personnel.
Note 3: If the mass flow controller is to be used on a gas other than the
calibration gas, apply the appropriate sensor conversion factor. Size the
orifice for actual operating conditions.
For the card edge model do not ground Pin 10 with the 5 Volt reference
enabled. Irreparable damage to the PC board may result.
CAUTION
Note 4: If Brooks secondary electronics are being used as a power supply
during the calibration the 5 V reference must be enabled on the Card Edge
version for proper operation, see Section 2-12. Remember to deactivate
the 5 V reference before installing the calibrated mass flow controller in the
system where Terminal 10 is grounded.
a. With the controller installed in an unpressurized gas line, apply power
and allow approximately 45 minutes for warm-up. During the warm-up,
adjustment and calibration check procedures do not allow the control
valve to open when gas flow is not present. This situation is not a
normal operating mode, it will cause the control valve to heat up
abnormally. A meter with an abnormally warm valve will be difficult to
calibrate. This situation can be prevented by switching the valve
override "closed" when there is no gas flow, or setting the command to
less than 1%. Also avoid unnecessary periods with the valve override
"open".
b. Adjust the anticipate potentiometer fully clockwise (20 turns). Then
adjust the anticipate potentiometer 10 turns counterclockwise to center
the potentiometer. This will provide a rough adjustment of this circuit
and make the flow more stable for calibration.