Why did my temperature sensor die?

02 May 2019

Why did my temperature sensor die? Early engineering analysis matters for critical applications

Temperature sensors used in harsh environments face numerous threats to survival. Failures are usually driven by external forces including thermal and mechanical shock, vibration, humidity, corrosion, radiation and dynamic thermal pressure cycling. Sensors subjected to these environments will ultimately fail, but how they handle the conditions over their lifespan is dependent on how they are made.

Early engineering design and analysis can dramatically increase the life expectancy of temperature sensors and yield the ideal sensor design. However, many companies are finding temperature sensor design is increasingly difficult due to:

  • Lack of in-house sensor development and exotic materials expertise
  • Shortage of analog electrical engineers
  • Increasingly harsh environmental operating conditions due to advanced product designs
  • Regulatory requirements
  • The Internet of Things (IoT) movement is proliferating the use of sensors to instrument, manage, and control complex processes

Analyze These 4 Areas to Avoid Sensor Failure:

  • End Use Application
  • Design & Material Selection
  • Manufacturing & Supply Chain
  • Project Execution & Regulatory Compliance

End Use Application Analysis:

Achieving a reliable sensor design requires a comprehensive understanding of the target use application, including:

  • Macro and micro location; proximity to other objects and surfaces
  • Process and equipment interfaces, and phases of matter to be encountered
  • Installation, set-up, operation, and maintenance conditions and constraints
  • Support documentation to meet product, project, and supplier quality requirements
  • All external factors that will contribute to the aging of the sensor

Temperature sensors are passive components that degrade when operating in the presence of harsh environments. Oftentimes the review of these application requirements will preclude the use of an off-the-shelf sensor as they will be destroyed in a short period of time. It is critical during the engineering analysis phase to understand the use and application requirements for the sensor design.

Design & Material Selection:

The quality of the materials in a temperature sensor system has a massive effect on its lifespan in a given harsh environment. After thoroughly understanding the application, the following engineering analysis should be performed to design the ideal temperature sensor:

  • Define critical sensor design parameters to achieve application performance goals
  • Define the sensor element layout and packaging to protect the sensor
  • Identify and select materials and ensure material performance ratings are suited to the application operating environment conditions
  • Model material interfaces to minimize thermal expansion and hysteresis issues
  • Ensure fit and tolerances with all equipment and application interfaces

Each of these steps is closely related and may require multiple iterations to arrive at the ideal design. Specifying materials and designing the ideal sensor are critical to project success; the ability to deliver custom sensors consistently is another overlooked factor in overall sensor system selection.

Manufacturing & Supply Chain Analysis:

When an application requires an ongoing, sustainable supply of sensors, inconsistent manufacturing can become a major root cause of sensor failures. Early in the engineering analysis phase, the ideal sensor design should be translated into critical manufacturing parameters that need to be measured and controlled. This phase should also include the definition of a calibration method that will ensure the sensor’s performance matches the end-use application’s requirements. Finally, a review of the supply chain should be conducted to ensure that the material sourcing meets traceability and quality requirements. This review should also be used to define the inventory strategy that best matches the scheduled project and/or factory consumption patterns.

Project Execution & Regulatory Compliance:

Regulations pertaining to sensor use vary greatly by market. Compliance with these regulations can preclude the use of some off-the-shelf sensors.  Non-compliance can result in sensor failure and have negative safety and legal ramifications. Regulatory compliance should be analyzed early in the engineering analysis phase to determine its impact on the overall project schedule. This includes understanding regulatory impacts on all aspects of documentation, design control, quality control, manufacturing control, supplier control, materials traceability and history retention requirements.

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