Brooks Instrument 5866M - Manual (Page 4)

1-1
Introduction
Introduction
1-1 Purpose
This instruction manual is intended to provide the user with all the
information necessary to install, operate and maintain the Brooks
® Model
5866 Pressure Controller. This manual is organized into seven sections:
Section 1 - Introduction
Section 2 - Installation
Section 3 - Operation
Section 4 - Maintenance
Section 5 - Troubleshooting and Repair
Section 6 - Calibration
Section 7 - Spare Parts
It is recommended that this manual be read in its entirety before attempting
to operate or repair the Model 5866.
1-2 Description
The Brooks Model 5866 Pressure Controller accurately measures and
controls upstream or downstream pressures. The heart of the system is a
solid state pressure transducer which produces an electrical output
proportional to pressure. The electronics use this signal to operate the
control valve and to provide an output signal.
1-3 Principle of Operation
The pressure to be measured acts on a stainless steel diaphragm. Via
silicone oil, this pressure is transmitted to the actual sensing element, a
silicon chip (refer to Figure 1-1). The chip consists of an anisotropically
etched diaphragm with four piezo resistive resistors, configured in a
Wheatstone bridge, etched into its surface (refer to Figure 1-2). The
mechanical deformation of this diaphragm results in an imbalance of the
resistors which is proportional to pressure. An amplifier provides output to
the control circuit as well as the electrical output signal.
In addition to the pressure transducer the Model 5866 has an integral
control valve and control circuitry. A difference between the pressure and
setpoint signals will cause the electronics to modulate the control valve to
maintain the desired pressure. A system block diagram is shown in Figure
1-3.
The integration of pressure transducer, 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 1-4.
The “upstream pressure regulation mode” shown in Figure 1-5 places the
pressure controller at the outlet of the pressure vessel. The pressure in the
process upstream of the controller will be constant independent of
downstream variation. Pressure measurement and control takes place at
the outlet side of the pressure vessel.
Section
1