A P A S S I O N F O R P E R F E C T I O N

Total Pressure Measurement

Prepared by: Andreas Schopphoff

Date: 2012-10

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 2

Content

� Basics of Total Pressure Measurement

� Measurement Ranges

� Gas Type Dependent Measurement

� Medium Vacuum Measurement

� Pirani

� Ultra High Vacuum Measurement

� Hot Cathode Gauges

� Cold Cathode Gauges

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 3

Overview

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Measurement Ranges

A P A S S I O N F O R P E R F E C T I O N

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Measurement independent of gas type

� Pressure defined

� p=F/A

� F=force

� A=Area

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Commonly Used Units in Vacuum Technology

� SI Pascal Pa=N/m2

� Units used in vacuum technology

� 1 mbar = 100 Pa

� 1 Torr = 133,322 Pa

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Measurement dependent on gas type

� Pressure defined

� p = n KT

� n = particle number density

� K = Boltzmann’s constant

� T = thermodynamic temperature

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 8

Measurement Ranges

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 9

Content

� Basics of Total Pressure Measurement

� Measurement Ranges

� Gas Type Dependent Measurement

� Medium Vacuum Measurement

� Pirani

� Ultra High Vacuum Measurement

� Hot Cathode Gauges

� Cold Cathode Gauges

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 10

Pirani Gauge, Principle

� Heated wire (tungsten) 100 to 130°C

� Heat loss due to thermal transfer of gas

� Constant heating

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Characteristic Curve Pirani Gauge

0,0001

0,001

0,01

0,1

1

10

100

1000

0,0001 0,001 0,01 0,1 1 10 100 1000

True pressure (mbar)

Indic

ate

d p

ressure

(m

bar)

Stickstoff

Luft

Wasserstoff

Helium

Argon

Kohlendioxyd

Nitrogen

Air

Hydrogen

Helium

Argon

Carbondioxide

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 12

Summary: Pirani

� Measurement range: E-4 to 1000 mbar

� Accuracy + - 15 %

� Easy to use

� Can be mounted in any orientation

� Gas type dependent

� Easy to clean

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 13

Content

� Basics of Total Pressure Measurement

� Measurement Ranges

� Gas Type Dependent Measurement

� Medium Vacuum Measurement

� Pirani

� Ultra High Vacuum Measurement

� Hot Cathode Gauges

� Cold Cathode Gauges

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 14

Hot Cathode, Principle

A P A S S I O N F O R P E R F E C T I O N

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Differential Ionization

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Bayard Alpert: X-Ray Effect

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Ion Source: Trajectories

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Bayard Alpert: ESD Ions

A P A S S I O N F O R P E R F E C T I O N

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Extractor Ion Gauge

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Summary: Hot Cathode Gauge

� Measurement Range: E-12 to E-1mbar

� High Accuracy + - 10 to 15 %

� Sensitive to conatmination

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 21

Cold Cathode Sensor: Principle

A P A S S I O N F O R P E R F E C T I O N

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Cold Cathode Sensor

A P A S S I O N F O R P E R F E C T I O N

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Magnetron

� According to Redhead

� Additional electrodes

� p = E-13 mbar

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 24

Summary: Cold Cathode Gauge

� Measurement Range E-11 to E-2 mbar

� Accuracy + - 30%

� Rugged

� Easy to clean

� Not useful with sputter applications

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 25

The Right Gauge for the Application

� Measurement Range?

� Accuracy?

� Gases?

� Environment?

A P A S S I O N F O R P E R F E C T I O N

© Pfeiffer Vacuum 2012 • Market Management R&D • Andreas Schopphoff • 2012-06-21 ■ 26

Gauges with external Controller

GaugeElektronic TPG 300

Up to 500m

A P A S S I O N F O R P E R F E C T I O N

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End

� Thank you for your attention!