3-3
3.1.4 Gas Flow Controls and Indicators
Pressure Regulator and Gage
Turning the regulator knob(s) clockwise increases pressure, counter-clockwise
decreases pressure; pushing in on the knob locks the setting. The pressure gage
indicates the setting.
Note: When adjusting the regulator(s) to the required pressure, make sure that
the process is either stopped or that the regulator is not supplying gas to the
furnace. Although a pressure regulator is a dynamic device, in this type of
application it has to be set at zero flow.
Flowmeter
Turning the control valve clockwise decreases flow, counter-clockwise increases
flow.
Note: Flowmeters of this type are calibrated to discharge at atmospheric
pressure and will not read correctly unless the chamber exhaust valve is open.
When the chamber exhaust valve is closed, the reading will continually decrease
as the chamber pressure increases and reaches equilibrium.
Compound Pressure Gage
This gage indicates the level of vacuum or pressure in the chamber on a
continuous basis.
Digital Vacuum Gage, (Optional on 120 Volt Models/Required on 220 Volt
Models)
This gage indicates the vacuum level in the chamber on a continuous basis. The
instrument is auto-ranging, switching between units of torr or millitorr depending
on the vacuum level. Note: On 220 volt models SP1 is set to 5 torr, SP2 to 900
millitorr; these settings are used by the control system to inhibit heat until
vacuum levels are sufficiently low enough to prevent arcing due to plasma.
3.2 ¼ DIN Ramping Controller
The Model 1200 Table-Top furnace system features a Watlow Series F4 ¼ DIN
Industrial Controller. Please refer to Figure 3.3 at end of this section for an
illustration of the controller. The F4 includes the following:
• Four-line high resolution LCD display.
• Guided setup and programming software.
• 16-bit microprocessor.
• 40 variable-length nameable profiles with up to 256 ramp steps.
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