Ionization Gauge Leakage Current Detection and Decontamination

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Solution Overview

Problem

Hot cathode ionization vacuum pressure gauges suffer from conductive contamination on electrical feedthrough insulators, leading to leakage currents that cause inaccurate pressure measurements and reduce gauge lifetime, necessitating a solution to measure and mitigate these issues in situ without removing the gauge from its operational environment.

Innovation Solution

A device and method that includes an electrical circuit configured to test and respond to leakage currents in hot cathode ionization gauges, allowing for in situ measurement and decontamination of feedthrough insulators while under vacuum, using a microcontroller to apply corrections to pressure measurement signals and electron emission currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrical feedthrough insulators are used to prevent leakage currents, then electrical isolation is maintained, but conductive contamination builds up on the insulators causing leakage currents to flow

Engineering Contradiction:

Improveelectrical isolationVSAvoidconductive contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies the 'Blessing in disguise' principle by using the harmful leakage current itself as a diagnostic signal. The system intentionally applies a test voltage to the contaminated insulator and measures the resulting leakage current, converting the harmful effect into useful information about the contamination level. This measured current is then used to correct pressure measurements and extend gauge operation without removal for cleaning.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Measurement precision

If leakage current measurement and correction systems are implemented, then pressure measurement accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvepressure measurement accuracyVSAvoidelectrical circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies the 'Universality' principle by designing the test circuit to serve multiple functions: it measures leakage current, diagnoses contamination levels, corrects pressure measurements, and monitors insulator condition all through a single integrated electrical circuit. The microcontroller executes multiple diagnostic and correction algorithms using the same hardware infrastructure, reducing the need for separate specialized components for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent applies the 'Intermediary' principle by introducing a test voltage source and measurement circuit as an intermediary between the contaminated insulator and the pressure measurement system. This intermediary circuit isolates the contamination effect, measures it separately, and then allows the main pressure measurement system to operate independently while applying corrections based on the intermediary's measurements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If in situ decontamination is performed by electrically heating contamination, then insulator cleanliness is improved, but energy consumption increases

Engineering Contradiction:

Improveinsulator cleanlinessVSAvoiddecontamination energy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies the 'Periodic action' principle by implementing decontamination as an intermittent process rather than continuous operation. The system periodically applies elevated voltage to electrically heat and remove contamination from the insulator, then returns to normal measurement operation. This periodic approach maintains insulator cleanliness over time while minimizing energy consumption compared to continuous heating.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach improves pressure measurement accuracy and extends gauge lifetime by enabling in situ leakage current measurement and correction, reducing the need for service and maintaining accurate pressure readings even at low electron emission currents.

Implementation Method 1

The electrical circuit can be further configured to electrically heat the contamination by increasing the voltage across the electrical feedthrough insulator to increase current passing through contamination on the insulator

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

ions are generated by electron flow between the cathode and anode

Methodology Applied

Scientific EffectIonization: Ionisation

Data Source

PatentUS10132707B2Devices and methods for feedthrough leakage current detection and decontamination in ionization gauges

Publication Date: 2018.11.20 MKS INSTR INC

AI summary

Devices and corresponding methods can be provided to test an ionization gauge, such as a hot cathode ionization gauge, for leakage currents and to respond to the leakage currents to improve pressure measurement accuracy. Responding to the leakage current can include applying a correction to a pressure measurement signal generated by the gauge based on the leakage current. Responding to the leakage current can also include removing contamination causing the leakage current, where the contamination is on electrical feedthrough insulators or other gauge surfaces. Testing and correcting for leakage currents and removing contamination can be completed with the ionization pressure gauge in situ in its environment of use, and while the gauge remains under vacuum.