Chapter One: General Information
Introduction
17
Chapter One: General Information
Introduction
The Type 146C Cluster Gauge
Vacuum Gauge Measurement and Control System is a versatile,
½ rack instrument which can power and provide concurrent readouts for up to four different
vacuum gauges, or a combination of gauges and flow controllers. The instrument can support
capacitance manometers (4, 5, or 6 decade), Pirani, and ion gauges. A Dual Channel feature
automatically switches from one gauge to another, thus providing the potential for a continuous
pressure reading display from 10
-10
to 10
3
Torr. The channel in the main display can
automatically switch from a rough vacuum gauge to a high vacuum gauge during pumpdown or
backfill. The 146 unit can accept a user-defined set point to operate a flow controller. If more
than one flow controller is used, a Totaling feature allows one controller to control the total flow
of all the controllers combined. With the optional Control board installed, the 146 unit can
govern an upstream solenoid valve, a downstream throttle valve, or one or more ratio controllers
in a closed-loop pressure control system.
The 146 unit arrives from the factory with four default recipes, each with an individual set point,
phase lead, and gain setting. The recipes can easily be customized to meet the needs of different
applications. By using the keyboard on the front panel, operators can: set alarm relay parameters,
display pressure or leakage readings, choose display units (Torr, Pascal, mbar), and configure
communication data. Control parameters such as base, lead, gain, integral, softstart, and start can
also be adjusted through the front panel. Gauges can be zeroed and spanned individually, or
cross-calibrated for span. There is an automatic ion gauge powerdown at high pressures, and a
sensor powerdown for cryo-pump regeneration. The non-volatile memory stores all parameter
entry values as well as sensor data such as capacitance manometer zero correction, and HPS
Pirani spans. Diagnostic tests are included for basic troubleshooting.
The 146 instrument has a front panel window with a 4½ digit main display, and three 2½ digit
displays. The LCD window is backlit with an electro-luminescent lamp, and has an automatic
one-hour timeout. Although the LCD is readable without backlighting, any keystroke re-
illuminates the backlight in addition to performing its usual function. All commands can be
activated through the front panel, or the unit can be controlled via an interface with a computer
through an RS-232 serial communication link. A front panel lockout feature disables command
control through the front panel (except for the [
QUIET
/
CANCEL
] key). The 146 unit front panel
lockout commands are entered through the available digital control lines or RS-232 messages.
Another option is the displayless unit. Here, 146 units have their normal front panel replaced
with a panel that has only a power switch, LED, and 25-pin Type “D” connector. One or more of
these displayless units can be placed in remote locations and controlled through a portable front
panel which has the normal display, or through RS-232 communications. The panel can be
connected to each remote unit in turn with a ribbon cable. In summary, the 146 instrument is
designed to allow operators the ability to calibrate gauges; control and fine tune their pressure
system, and still provide flexibility for system upgrades.
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