Vector 750 Watt Power Inverter User Manual download pdf (Page 22)

that is within the valve. A flat spring centers the

armature and also provides a countering force to the

magnetic field. The usual arrangement is normally

closed - when no current is applied to the solenoid the

face of the armature rests on the orifice. This face may

have an elastomeric material to seal the valve or it may

be a metal-non sealing configuration. It should be noted

that control valves of this type are not meant to be

positive shut off devices. If a positive shutoff is

required, there should be a dedicated isolation valve

downstream of the control valve.

The action of the valve is as a variable conductance

with very high resolution. Proportioning valves are

designed to be used as part of a closed loop control

system with constant feedback. They are not designed as

“set and forget” valves as the armature position will

wander without constant correction.

The orifice is sized to the flow range required by

application, and manufacturers will offer a range of

flows and guidelines for selection. A typical offering

would be several ranges from 10 sccm to 10,000 sccm.

withthe flow rating based on the orifice size under

typical upstream and downstream pressure conditions

the Bell Jar, Vol. 10, No. 3/4, Summer/Fall 2001

Figure 5 -

Figure 6 -

Vacuum Chamber

Pressure

Gauge

Proportioning

Valve

Throttle Valve

To Pump

Gas

Supply

Set Point Input

Pressure

Reading

Deviation

Error

Figure 4 - System with Upstream PID Pressure Control

Control

Voltage

Solenoid

Orifice

Spring

Armature

Figure 5 - Solenoid Proportioning Valve

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Vector 750 Watt Power Inverter User Manual Page 22

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