The piezoelectric gas dosers from
Oxford Applied Research are high quality all-metal (no elastomers) UHV compatible
dosers which are actuated by means of an internal piezoelectric crystal stack. Application
of a voltage to the stack causes it to extend thereby lifting a ceramic plunger
which, unenergised, is sealed to the valve seat by a high tension spring.
This design provides fail-safe operation
such that in the event of power failure, the valve automatically closes preventing
venting of the system. Power is provided for the valve by a compact supply, permitting
remote control which is particularly advantageous where the valve is situated in
inaccessible or hazardous locations. The linear extension of the piezo-stack with
voltage preserves the relationship between leak rate and old-style manual control
knob position, as shown in the adjacent graph. Greatest control is provided where
it is needed most - in the extremely low flow regime. |
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