MKS T3PIA, Instruction Manual, Page: 33 / 70

General Information Chapter Three: Product Overview
25
Chapter Three: Product Overview
Note
Before continuing with the information in this chapter, be sure to have worked through all
descriptions and procedures in Chapter Two.
General Information
The T3P consists of a throttle valve, a microprocessor, an RS-232 communications interface, analog inputs
for pressure or position control, and analog outputs that reflect the pressure or valve position.
Valve Safety
MKS products are designed and tested to provide the highest degree of safety attainable. To use your MKS
valve safely, you must always conform to the following instructions:
„
Refer to Chapter Two for directions on installation and operation of the valve.
Warning The moving parts in the valve create a risk of personal injury until the valve is
securely incorporated into a system. To avoid injury keep all objects away from
any valve opening.
„
Do not insert objects into openings where contact with moving parts is possible.
„
Isolate the equipment from any electrical or pneumatic power supply before handling the valve.
Control Mode
The T3P controls pressure in a vacuum system using either Pressure or Position control.
Parameters for the control modes are adjusted and viewed via digital communications.
In Pressure Control , the T3P unit moves the valve in order to maintain a desired pressure (the setpoint). The
controller uses either a Model Based or a Proportional, Integral, and Derivative (PID) algorithm to determine
the valve position and make position adjustments. With Model Based, the control algorithm uses the current
pressure, position, and setpoint readings to calculate the next valve position during each control cycle. With
PID, the setpoint uses two parameters—the phase and gain—to optimize the response from setpoint to
setpoint. Although there are default values for these parameters, you should adjust the values for optimum
control (refer to
Tuning the Controller in the MKS Type T3BIA/T3PIA Valves with RS-232 Interface
Supplement , for more information). The feedback is an analog pressure signal. This signal is normally 0 to 10
Volts, but the zero and full-scale voltages can be adapted to individual applications.
In Position Control, the T3P unit moves the valve to a desired position (the setpoint). In this mode, the valve
is moved to the desired setpoint but no feedback signal is generated. It is not necessary for the controller to
make adjustments once the valve reaches its setpoint.