Sensor Element Metal Platelet Corrosion Protection

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Solution Overview

Problem

Conventional sensor elements for measuring physical variables in media suffer from reduced long-term stability due to corrosion of passivating layers when in direct contact with the measured medium, which also decreases their sensitivity and response time.

Innovation Solution

A sensor element design featuring a planar substrate with a functional layer, a passivating layer, a metal connecting layer, and a metal platelet that prevents direct contact between the passivating layer and the medium, using a contact layer and a plastics layer to protect the metal connecting layer and substrate, allowing direct contact without degrading stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the sensor element is protected with a passivating layer and used in direct contact with the measured medium, then the long term stability is improved, but the sensitivity and response time are degraded due to corrosion of the passivating layer

Engineering Contradiction:

Improvelong term stabilityVSAvoidcorrosion of passivating layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A metal platelet is introduced as an intermediary protective element between the passivating layer and the measured medium. The platelet is applied on the passivating layer in a corrosion-resistant manner, preventing direct contact between the passivating layer and the aggressive medium while maintaining thermal coupling for sensing functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The metal platelet is applied as a thin film or layer on the passivating layer surface. This thin protective layer prevents corrosion while minimizing thermal mass addition, thereby preserving the sensor's response time and sensitivity characteristics.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If metal sleeves are used to protect sensor elements from the process medium, then the long term stability is improved, but the response time and sensitivity are significantly degraded due to increased thermal mass

Engineering Contradiction:

Improvelong term stabilityVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of thick metal sleeves, a thin metal platelet layer is applied directly on the passivating layer. This thin-film approach provides corrosion protection while adding minimal thermal mass, thereby maintaining fast response times and high sensitivity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The metal platelet is applied locally only where needed for corrosion protection on the passivating layer surface, rather than enclosing the entire sensor in a thick metal sleeve. This localized protection minimizes thermal mass addition while providing adequate protection against the measured medium.

Inventive Principle:

Principle #3Local quality

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

The sensor element maintains high sensitivity and short response time while preventing corrosion, enabling long-term stability and safe operation in direct contact with aggressive media.

Implementation Method 1

By means of this functional layer, the temperature of a medium in thermal interaction with the functional layer can be determined

Methodology Applied

Scientific EffectThermal interaction: Conduction (thermal)

Implementation Method 2

a metal platelet, which is applied in such a manner on the surface of the metal connecting layer that in the case of a contact of the sensor element with the measured medium no contact occurs between the passivating layer and the measured medium

Methodology Applied

Scientific EffectPhysical barrier protection: Physical Containment

Implementation Method 3

thermal flow sensors are composed of a plurality of these sensor elements, usually a low-ohm heating element and a high-ohm resistance element

Methodology Applied

Scientific EffectThermal energy transfer: Conduction (thermal)

Data Source

PatentUS11092471B2Sensor element and thermal flow sensor for determining a physical variable of a measurement medium

Publication Date: 2021.08.17 INNOVATIVE SENSOR TECH IST

AI summary

The present disclosure resides in a sensor element for determining a physical, measured variable of a measured medium, comprising: a planar substrate; a functional layer applied on a surface of the substrate; a passivating layer applied on the functional layer; a metal connecting layer applied on the surface of the passivating layer such that the passivating layer is completely covered; and a metal platelet applied on the surface of the metal connecting layer such that no contact can occur between the passivating layer and the measured medium, as well as residing in a thermal flow sensor, which has at least two such sensor elements.