Gamry VistaShield Stir/Purge, Operator'S Manual

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Chapter 5: Panel Indicators and Controls--Front panel
5 - 3
GAS Toggle and LED
The GAS Toggle and LED are located to the left of the STIR Toggle and LED. The PURGE function of the
Stir/Purge is controlled by a three-position GAS toggle switch and by the FLOW RATE knob. The three positions
of the GAS toggle are (top to bottom) PURGE, BLANKET, and REMOTE:
• When the switch is set to REMOTE, the Digital I/O connector controls the gas operation as described
below.
•
When set to BLANKET, the gas flow is directed out of the BLANKET port on the back of the Stir/Purge
chassis.
• When set to PURGE, the gas flow is directed out of the PURGE port on the back of the Stir/Purge chassis.
The LED above the toggle switch is lit whenever the gas flow is directed to PURGE, whether manually via
the toggle or through software when the switch is set to REMOTE. The default behavior with the Gamry
Framework software is that blanket gas flows before, during, and after an experiment. The purge gas flows
only when performing the stir/purge operation.
FLOW RATE Knob
The FLOW RATE knob is located on the left side of the Stir/Purge front panel. The knob is connected directly to
a needle valve. Turning the knob in a counterclockwise direction opens the valve and increases the gas flow
directed to either PURGE or BLANKET port depending on the GAS Toggle position. While the individual
components are rated to 30 psi gauge, the system as a whole is rated to 10 psi, which is generally low enough
that wire tie-downs on hose-connections to barbs are not necessary. Gamry suggests starting with the gas FLOW
RATE control off and increase slowly until you get a reasonable bubbling.
There is no indication or recording of whether gas is flowing or how much gas there is. Therefore, the user must
determine both that the gas flow is on and that the flow rate is appropriate. Gas-flow rate is not controlled by
the REMOTE connector. The REMOTE setting only controls whether gas is directed to the PURGE or BLANKET
port.
The gas FLOW RATE control is reversed compared to many common flow control
devices, such as cold water taps. The knob is turned in a clockwise direction to turn off or
lessen the gas flow.
Gas Toggle
and LED
Gas FLOW
RATE Knob