Fujikura O2 Sensor Replacement Without Redesign

When Is a Full Redesign Really Necessary?

The discontinuation of Fujikura oxygen sensors has left many OEM manufacturers asking the same question:

Can we replace the sensor without redesigning the entire system?

In many applications, the answer is yes.

Although Fujikura sensors are no longer available, replacing them does not necessarily require a complete redesign of the electronics, PCB, firmware, or mechanical assembly. The level of engineering effort depends on how the original sensor was integrated and which aspects of the system are critical to the application.

A replacement sensor does not need to be electrically and mechanically identical in every detail to be suitable. Successful migration depends on evaluating the complete system and identifying only the changes that are required.

Because Fujikura and Sensore oxygen sensors use the same limiting current ZrO₂ measurement principle, much of the existing system architecture can often be retained.

This article explains which areas should be reviewed, where changes may be required, and how OEM manufacturers can transition away from discontinued Fujikura sensors while minimizing redesign, validation effort, and production disruption.

Table of contents

Start by Understanding What Really Changes
Where Changes Are Most Common
PCB Mounting Considerations
The Biggest Mistake OEMs Make
Validate Before You Redesign
OEM Migration Checklist

Start by Understanding What Really Changes

When replacing a discontinued component, many engineers begin by comparing datasheets line by line. While technical specifications are essential, a direct comparison does not always show how easily a replacement can be integrated into the existing system.

For Fujikura replacements, it is important to distinguish between the sensing technology itself and the surrounding system architecture.

Although Fujikura and Sensore sensors differ in some mechanical and electrical characteristics, both use the same limiting current ZrO₂ measurement principle.

This allows much of the existing system architecture to be retained, while only application-specific differences need to be reviewed.

Instead of asking “Is this sensor identical?”, a more useful engineering question is:

“Which differences are relevant to my existing system?”

In many OEM designs, the answer is fewer than expected.

For OEM manufacturers evaluating replacement options, understanding the technical differences between Fujikura and Sensore oxygen sensors is an important step in the migration process. Explore our Fujikura replacement solutions and sensor comparison resources to evaluate available alternatives.

Where Changes Are Most Common

The effort required depends on how the original Fujikura sensor was integrated into the product. Rather than redesigning the complete system, engineers should review four key areas.

Mechanical Integration

The most obvious differences are mechanical rather than functional.

Most Sensore sensor types are mechanically compatible with the corresponding Fujikura footprint, although some differences in housing design and sensor orientation should be considered during integration.

Areas to verify include:

Sensor footprint and orientation
Available installation space
PCB clearance
Sensor positioning and airflow
Assembly method

For many OEM applications, the existing mechanical architecture can therefore be retained.

PCB and Sensor Footprint

Another area that often generates unnecessary concern is PCB compatibility.

Fujikura sensors use five pins, whereas Sensore sensors use four. At first glance, this appears to represent a major electrical difference, but the additional Fujikura pin serves only as a mechanical orientation feature and has no electrical function.

Sensore indicates orientation through a mechanical feature on the housing, following a common approach used across electronic component design.

Similarly, although the PCB footprints are not completely identical, many OEM manufacturers have successfully installed Sensore sensors onto PCBs originally designed for Fujikura devices with only minor adaptations. Compatibility should always be verified for each PCB layout and manufacturing process, but footprint differences alone do not necessarily require a board redesign.

Electrical Integration

Mechanical compatibility is only one part of the replacement process. The existing electronics should also be reviewed to determine whether any adjustments are required.

Fujikura and Sensore sensors use the same limiting current ZrO₂ measurement principle, but differ in some electrical operating parameters. Fujikura sensors require individual heater voltage adjustment, while Sensore sensors operate with a defined fixed heater voltage. This simplifies sensor integration and replacement.

Engineers should review:

Heater operating conditions
Sensor bias voltage
Sensor output characteristics
Signal conditioning
Existing electronics and firmware
System calibration

Depending on the existing Fujikura electronics and the selected Sensore sensor, much of the existing electrical architecture may be retained. A review of the complete measurement chain helps identify whether any adjustments are required and which Sensore sensor is best suited as a replacement.

Heater Control Can Simplify the Migration

One important difference between Fujikura and Sensore sensors is heater operation.

Fujikura sensors require the heater voltage to be adjusted individually for each sensor, while Sensore sensors operate with a defined fixed heater voltage for each sensor type. This eliminates the need for sensor-specific heater voltage adjustment and can simplify integration, production and sensor replacement.

For specific Fujikura replacement applications, Sensore can also provide sensor variants with adapted heater characteristics to support integration with existing Fujikura electronics. The appropriate sensor configuration should be selected based on the existing electronics and application requirements.

Don’t Let the Housing Differences Mislead You

Sensore and Fujikura sensors differ in their external construction, but both use the same limiting-current ZrO₂ measurement principle.

One visible difference is the protective design around the sensing element. Sensore uses a protective mesh on top of the sensor, while Fujikura uses a different mesh construction around the sensing element.

Both designs allow the surrounding gas to reach the sensing element while providing mechanical protection. Although the housing designs differ, the underlying measurement principle remains the same. Sensor positioning and airflow should therefore be considered during system integration.

Although the designs look different, both serve the same purpose:

Protecting the sensing element
Allowing gas diffusion
Maintaining reliable oxygen measurement
Reducing contamination reaching the sensor

For most applications, these design differences do not change the overall migration strategy, although airflow characteristics should always be verified during system validation.

PCB Mounting Considerations

Fujikura sensors use an insulating molded base plate, allowing the sensor to sit directly on the PCB without creating electrical contact.

Sensore sensors use a metal base plate instead. If the base plate touches conductive areas on the PCB, there is a potential risk of an electrical short circuit.

For this reason, Sensore typically recommends maintaining a clearance of approximately 2–3 mm between the PCB surface and the sensor base during assembly.

To simplify production, an optional insulating spacer can also be fitted beneath the base plate. This provides electrical isolation while enabling easier, more consistent assembly, particularly in high-volume manufacturing environments.

For many OEMs, this small mechanical adaptation is sufficient to eliminate the risk without requiring significant changes to the PCB design.

Replacing a Fujikura oxygen sensor without redesigning an OEM system

The Biggest Mistake OEMs Make

Replacing a discontinued Fujikura sensor does not automatically require a complete system redesign. Before making design changes, OEM manufacturers should review how the selected Sensore replacement interacts with the existing electronics, mechanical setup and application conditions.

This system-level assessment helps identify any necessary adjustments early while retaining as much of the existing design as possible.

Sensore supports customers throughout this process, from sensor selection and technical evaluation to integration and qualification.

Validate Before You Redesign

A common misconception is that replacing a discontinued sensor automatically requires a complete redesign of the product. Many migration projects involve fewer changes than initially expected.

Successful replacements begin with a structured engineering assessment that identifies where modifications are genuinely required and where the existing design can be retained.

By reviewing mechanical integration, electronics, firmware, manufacturing requirements, and validation together, OEM manufacturers can often preserve much of their existing architecture while reducing development time and qualification effort.

Sensor replacement should therefore be approached as a system integration project rather than a simple procurement decision.

OEM Migration Checklist

Before implementing a Fujikura replacement, verify:

Suitable Sensore replacement selected
Mechanical integration and PCB clearance checked
Electrical operating conditions reviewed
Signal processing and calibration verified
Performance validated under application conditions

Conclusion

Replacing a discontinued Fujikura oxygen sensor can often be achieved without redesigning the entire OEM system.

With the right Sensore replacement and a structured technical evaluation, OEM manufacturers can minimize integration effort while maintaining product and supply continuity.

Our team supports customers throughout the replacement process to find a solution that fits both the existing system and the application requirements.

Related Resources

Need Support with Your Fujikura Sensor Migration?

Every OEM application is different. Our engineering team can help evaluate sensor compatibility, identify required modifications, and define a practical migration path from obsolete components to a qualified replacement solution.

Replacing a Fujikura Oxygen Sensor Without Redesigning Your OEM System