Brooks Instrument SLA5840 - Manual (Page 19)

3-1
Brooks ® Model SLA5840
Section 3 Operation Installation and Operation Manual
X-PR-SLA5800-RT-eng
Part Number: 541B120AAG
August, 2009
3-1 Overview
This section contains the following information:
• Theory of Operation
• Features
3-2 Theory of Operation for RT
A user supplied pressure sensor, with a full scale pressure as low as
10 mTorr or as high as several hundred psi and a full scale output signal of
5 or 10 Vdc, monitors the pressure in a vessel or a feed or exhaust line
from the vessel. The control electronics in the Model 5866RT compare the
pressure signal to a setpoint and act to regulate the flow through the
integral solenoid control valve to stabilize the pressure at the setpoint. An
integral mass flow sensor identical in design to the Brooks Model 5860E
provides a 5 Vdc full scale signal proportional to the flow through the
control valve. A system block diagram is shown in Figure 1-1.
The integration of mass flow sensor, control electronics and control valve
into one unit results in a compact size. The mounting dimensions are
comparable to a mass flow controller. Refer to Figure 1-2.
In the upstream pressure regulation mode shown in Figure 1-3, the
pressure controller is placed at the outlet of the pressure vessel. The
pressure in the process upstream of the controller will be constant
independent of downstream variation. Pressure control takes place at the
outlet side of the pressure vessel.
3-3 Features
Note: All Brooks Digital Series mass flow meters are configured at the
factory according to customer order and do not require adjustment. Not all
features are available on all instruments.
The Brooks Digital is a full-featured digital MFC. The Brooks Digital
performs much like a traditional analog MFC, but with improved accuracy,
step response and valve control. The analog interface matches that of
Brooks' popular analog MFCs so it can be retrofitted into tools using
analog MFCs. Other versions of the Delta Class can provide a variety of
digital protocols, for example DeviceNet and RS-485.
The Brooks Digital equipment is capable of storing up to 10 different sets
of gas calibration data. Each set includes a calibration curve, PID controller
settings, valve performance data, and information about the calibration
conditions. The Brooks Digital equipment can contain calibrations for
different gases or for the same gas at multiple conditions (pressures, full-
scale flow rates). Section 3-4 Analog I/O Mode of Operation describes
more information about the data contained in the calibration table and how
to access the data.