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OPTOELECTRONICS POTENTIOMETERS
Selecting resistors for aerospace and defence electronics often includes reviewing the applicable qualification requirements at an early stage. For component engineers, however, that is rarely where the evaluation ends.
Qualification reports provide the evidence that a resistor design has successfully completed the recognised electrical, mechanical and environmental testing. Qualification evidence provides an important assessment of the design and manufacturing process against defined requirements. Engineers may still need to examine ongoing process controls, lot acceptance, change management and application-specific performance when assessing long-term programme suitability.
As platform lifecycles continue to increase and supply chains evolve, engineers are increasingly evaluating not only whether a resistor has been qualified, but also how it is manufactured, how it performs under application-specific conditions and how effectively the supplier can support the programme over the long term.
Qualification demonstrates capability. Ongoing production demonstrates repeatability.
What Happens After Qualification?
Standards such as MIL-PRF-55342, IEC 60115 and ESCC are fundamental to component selection, providing recognised methods for evaluating environmental endurance, mechanical integrity and electrical stability. Typical qualification programmes include load-life endurance, temperature cycling, moisture resistance, vibration, mechanical shock and short-time overload. Key electrical parameters such as resistance and temperature coefficient of resistance (TCR) are verified before and after testing.
For component engineers, these results establish confidence that the resistor design is suitable for its intended application. A key next step is determining whether that level of performance can be consistently reproduced throughout production.
Material selection, substrate quality, thick-film deposition, firing profiles, laser trimming and passivation all influence long-term electrical stability. Equally important are the manufacturing controls behind those processes. Statistical process control (SPC), lot traceability and disciplined engineering change management help ensure production devices continue to perform consistently with the original qualified design. At TT Electronics, more than 40 years of manufacturing experience, supported by millions of component-hours of load-life testing, provides valuable engineering evidence to support long-term reliability assessments and the FIT estimates used during system reliability modelling.
For programmes expected to remain in service for twenty years or more, this depth of manufacturing knowledge is every bit as important as successful qualification.
The Application Matters
Qualification testing evaluates components under a defined set of controlled stresses. Operational environments are rarely so predictable.
A resistor specified for an aircraft flight control computer is exposed to different electrical loading and environmental conditions than one used in a radar power supply, electronic warfare system or satellite communications subsystem. Understanding those conditions helps determine which qualification data deserves the closest scrutiny.
Beyond the qualification report, engineers should consider:
Taken together, these considerations help engineers interpret qualification data in the context of the intended operating environment.
Completing the Engineering Assessment
Completing the engineering assessment means understanding not only how a resistor performed during qualification, but how consistently that performance can be maintained throughout the life of the programme. Controlled manufacturing processes, disciplined engineering change management, production traceability and long-term product support all contribute to reducing both technical and supply chain risk.
Considering these factors alongside recognised qualification data provides a more complete picture of resistor suitability for demanding aerospace and defence applications.
Applying These Principles
These broader considerations are also relevant when evaluating the TT Electronics Welwyn CR Series of thick-film chip resistors.
Manufactured in Bedlington, United Kingdom, the CR Series uses established thick-film technology and is available across multiple package sizes, resistance values and tolerance options. The range is approved to applicable EN 140401 and CECC 40401 specifications and supports analogue, control, power-management and signal-conditioning functions in aerospace, defence and other long-life electronic applications.
Electrical ratings and qualification status remain central to the selection process, but they should be considered alongside the intended operating conditions and the manufacturing and programme controls available for the selected part. Depending on the application, these may include lot traceability, configuration control, change notification and continued product support.
Qualification therefore provides an important foundation for resistor selection. Combining that evidence with application-specific analysis and an understanding of the supplier’s manufacturing and lifecycle controls helps engineers make more complete component decisions for long-term programmes.
Woking, UK - 27, May 2026 - TT Electronics, a global provider of mission-critical power and sensing technology, has been selected to supply Hallogic® Hall-effect sensors for integration into fan assemblies on NASA’s Dragonfly rotorcraft mission. The sensors support a spacecraft subsystem where reliability and consistency are essential across the programme lifecycle.
Hallogic® Hall-effect devices, part of the Optek technology portfolio, are designed for non-contact motion sensing and switching, with variants processed and screened for military and space-grade applications where consistency and reliability are deisgn priorities.
Hallogic® OMH3075S is a high-reliability Hall-effect sensor in the Optek portfolio, designed for non-contact switching and operation across a broad range of supply voltages. The device is specified for operation from -55 °C to +150°C, supporting applications that require reliable switching across wide temperature ranges, and is suitable for military and space applications. For applications requiring enhanced screening, B and S versions are processed and screen to MIL-STD-883, with ESD Class 3B per the same standard.
Dragonfly is a rotorcraft lander mission to Saturn's largest moon, Titan, that is designed to conduct science across multiple locations, sampling surface materials to measure their detailed compositions, and observing geology and meteorology. The Johns Hopkins Applied Physics Laboratory (APL) manages the Dragonfly mission for NASA and is building the rotorcraft, which is scheduled to launch in 2028 and reach Titan in 2034.
"Dragonfly is a mission that demands exceptional reliability and consistency, and we’re proud that the Hallogic OMH3075S has been selected for this application,” said Klaus Zwerschina, VP Components, TT Electronics. “We work closely with customers to de-risk performance-critical designs, supporting programmes that value engineering continuity and a disciplined supply approach from design-in through production, for long service life."
About TT Electronics
TT Electronics is a global provider of engineered electronics for performance-critical applications. The company designs and manufactures solutions that enable a safer, healthier and more sustainable world. Serving key markets including healthcare, aerospace and defence, and industrial, TT Electronics partners with customers to deliver highly reliable solutions where failure is not an option.
Visit www.ttelectronics.com to learn more.
This TT Electronics white paper gives power system architects a practical framework for selecting, calculating, and maintaining optical isolation components designed to last 25 years in demanding grid environments.
Optical Isolation Fundamentals
How galvanic isolation has evolved into a critical performance enabler, including a breakdown of optical coupling mechanics and a comparison of five photodetector types mapped to their industrial applications.
CTR Calculations & Worst-Case Design
How to calculate the Current Transfer Ratio under real operating conditions — with a worked example showing how a nominal 200% CTR device can degrade to 129.2% in the field.
Reliability & LED Aging Mechanics
The Black Formula for predicting long-term CTR degradation, the Five Pillars of Optocoupler Longevity, and how to design for the 2σ worst-case population over a 25-year service life.
Advanced Applications & Compliance
SiC/GaN wide-bandgap driver requirements, integrated smart gate driver comparisons, and a plain-language guide to IEC 60747-5-5, partial discharge testing, and insulation standards.
In the landscape of industrial automation, the debate between maintaining fixed legacy systems and migrating to adaptable optical sensors is not just about technology; it is about operational philosophy. For decades, fixed optical systems—standard logic photocells, basic LED emitters, and fixed-gain optoisolators—have been the backbone of manufacturing. They are reliable, understood, and inexpensive.
However, the shift toward Industry 4.0 has exposed the limitations of these rigid systems. Engineers are now tasked with integrating components that can self-calibrate, communicate status, and adapt to environmental degradation. This article provides a transparent comparison between fixed legacy systems and modern adaptable optical sensors, covering Fibre Optics, Optoisolators, Photologic assemblies, and VCSEL technologies.
A fixed system operates on binary logic or set parameters defined at the hardware level. Once installed, its behaviour is static. For example, a standard infrared emitter paired with a phototransistor will trigger a signal when a light beam is broken. If dust accumulates on the lens, the signal degrades until the system fails. To fix it, a technician must physically clean the sensor or adjust a potentiometer.
Adaptable sensors utilise intelligent circuitry and superior materials (like VCSELs) to adjust to their environment. A programmable Photologic sensor, for instance, might dynamically adjust its hysteresis threshold to account for signal drift caused by temperature changes or debris. These systems prioritise data continuity and predictive maintenance over simple binary switching.
We must acknowledge why legacy systems remain prevalent. They are not without merit.
Lower Upfront BOM Cost – A standard fixed-gain optoisolator or a simple LED-based interrupter is significantly cheaper than a programmable alternative.
Simplicity of Replacement – If a fixed sensor fails, you pull it out and plug in an identical part. There is no firmware to update and no calibration software to run.
Zero Latency – Purely analogue fixed systems often have faster response times than smart sensors that require processing cycles to interpret data.
Legacy systems rely on standard LEDs. While functional, they suffer from beam divergence and lower power efficiency. Adaptable systems utilise Vertical-Cavity Surface-Emitting Lasers (VCSELs). VCSELs offer a narrow, coherent beam that requires less power and provides higher accuracy for position sensing. In adaptable systems, the VCSEL current can be modulated dynamically to maintain constant output power as the component ages.
A fixed system usually employs a discrete photodiode and a separate amplifier circuit. Adaptable Photologic sensors integrate the sensor, amplifier, and logic gate into a single package. The benefit is not just space; it is consistency. These adaptable units often feature internal voltage regulation and temperature compensation that fixed discrete circuits lack.
In high-EMI environments, copper is a liability. While legacy systems try to shield copper, adaptable systems switch to fibre optics. Modern industrial fibre optic links are adaptable because they provide complete electrical isolation and can be routed through hazardous areas where electrical sparks are prohibited. They are immune to the electromagnetic interference that plagues fixed copper legacy systems.
Engineers should consider migrating to adaptable sensors if:
Environmental variation is high – Varying light levels, dust, or temperature swings require sensors that can auto-calibrate.
Downtime is expensive – If stopping a line to wipe a sensor lens costs thousands of pounds, an adaptable sensor that compensates for occlusion is worth the investment.
Precision is critical – If you are moving from simple object detection to precise position sensing, VCSEL-based adaptable systems are required.
Fixed legacy systems are not obsolete, but they are becoming niche. For simple, cost-constrained applications where downtime is manageable, they remain a valid choice. However, for industrial engineers building systems for longevity, reliability, and Industry 4.0 integration, adaptable optical sensors offer a superior return on investment despite the higher upfront cost. By eliminating manual calibration and reducing failure points related to environmental stress, adaptable sensors future-proof manufacturing lines.
Written by TT Electronics
